Introduction

1,2,3-Triazoles and its derivatives have emerged rapidly with the advance of modern heterocyclic chemistry, promising a variety of medicinal applications such as antimicrobial (Demaray et al., 2008) anti-HIV (Lazrek et al., 2001) anticancer (Chen et al., 2011) and antioxidant (Khan et al., 2010) activities.

Chalcones are known to exhibit various biological activities (Alvarez et al., 1994), such as antioxidant (Sathyanarayana et al., 2004), anti-inflammatory (Mukherjee et al., 2001), antimalarial (Hsieh et al., 2000), antileishmanial (Ram et al., 2000) and anticancer (Zhai et al., 1999) activities. Furthermore, they have considerable biological importance, especially as pesticides (Anto et al., 1995). It is known that numbers of chroman derivatives are used as antioxidant for fats and oils (Bergmann and Gericke, 1990; Burrell et al., 1990; Gericke et al., 1991). Among naturally occurring chromans, vitamin E is very effective that suppress cellular membranes phospholipids degradation (Ray et al., 1976) and also exhibits antioxidant, anticancer and cardio protective activities.

During the past decades, the environment consciousness has compelled the chemist to make a new twist on old theme. In this endeavour, Microwave-assisted reactions have made a landmark and significant contributions to preserve the green environment by reducing the waste effluent, remarkable rate enhancement, high yields, greater selectivity and ease of manipulation.

Inspired with the biological profile of 1,2,3 triazoles, chalcones and chroman nuclei, their increasing importance in pharmaceutical and biological fields, and in connection with our (Ashok and Shravani, 2008; Ashok et al., 2012) search on the design and synthesis of pharmacologically important new heterocycles linked to chroman, it was thought worthwhile to synthesize the titled compounds with a view to obtain certain chemical entities with active pharmacophores in a single molecular framework.

Microwave-assisted organic synthesis is suited to the increased demand in industry because of short reaction times and expanded reaction range, In particular, there is a requirement in the pharmaceutical industry for a higher number of novel chemical entities to be produced.

Results and discussion

Chemistry

Herein, we wish to report an efficient, practical and high yielding method for the synthesis of compounds 8a–j and 13a–j. The starting materials 1-(7-hydroxy-2,2-dimethyl-chroman-6-yl)-ethanone (1) and 1-(5-hydroxy-2,2-dimethyl-chroman-6-yl)-ethanone (2) were prepared from the mixture of resacetophenone and isoprene using Amberlyst-15 catalyst in THF and heptanes (Kalena et al., 1997) shown in Scheme 1. The synthesis of titled compounds 8a–j and 13a–j was accomplished by two synthetic strategies and is shown in Schemes 2 and 3. In route-1 (Scheme 2), the chalcones 4a–j were synthesized from the mixture of compound 1 and aryl aldehydes in alcoholic KOH under microwave irradiation (MWI), followed by propargylation of chalcones 4a–j in dry acetone/K2CO3 gave compounds 5a–j. These compounds upon click reaction using CuI in DMF under MWI gave compounds 8a–j. In route-2 (Scheme 2), compound 6, prepared by propargylation of compound 1, followed by click reaction using CuI in DMF under MWI gave compound 7. Compound 7 on condensation with aryl aldehydes in alcoholic KOH under MWI gave compounds 8a–j in excellent yields than route-1 shown in Scheme 2. Compounds, 13a–j were also synthesized by the same procedure as compounds 8a–j shown in Scheme 3. By comparing the above routes, the target compounds were synthesized in excellent yields in route-2 (Table 3) to give overall yields of 90–95 % in short reaction time. Whereas in route 1, the overall yields are 50–60 % only and took longer time to complete the reaction. Initially, we have investigated the yields of the click reaction using CuSO4·5H2O/sodium ascorbate and CuI in different solvents like t-BuOH: H2O (2:1), THF and DMF under both conventional and MWI. In the above investigation, we produced higher yields using CuI in DMF under MWI (Tables 1, 2, 3).

Scheme 1
scheme 1

Synthesis of 1-(7-hydroxy-2,2-dimethyl-chroman-6-yl)-ethanone (1) and 1-(5-hydroxy-2,2-dimethyl-chroman-6-yl)-ethanone(2)

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Scheme 2
scheme 2

Synthesis of 1-[7-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-3-aryl-propenone (Route-1 and Route-2)

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Scheme 3
scheme 3

Synthesis of 1-[5-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-3-aryl-propenone (Route-1 and Route-2). Reagents and conditions: (a) Ar–CHO 3(a–j), KOH/EtOH, MWI (b) propargylbromide, dry acetone, K2CO3, reflux. (c) Benzylazide, (i) CuSO4·5H2O, Sodiumascorbate, H2O/t-BuOH (2:1), (or) (ii) CuI, DMF or THF, NEt3 RT or MWI

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Table 1 Screening of catalyst and solvent
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Table 2 Comparisons of conventional and microwave irradiation methods
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Table 3 Comparison of yields of 8a–j and 13a–j of route-1 and route-2
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Structures of synthesized compounds (5, 6, 8a–j, 11, 12, and 13a–j) were characterized by IR, 1H NMR, 13C NMR and mass spectral analysis. The 1H NMR spectrum of the representative compound 8a (dissolved in CDCl3 ) showed a singlet for Ar–H5 proton at δ 8.29, another singlet for Ar–H8 proton at δ 6.51. Two singlets for O–CH2 and N–CH2 protons appeared at δ 5.41 and 5.21 respectively. In the 13C NMR spectrum, the signal of C=O carbon appeared at 190.9 ppm, those of O–CH2 and N–CH2 C-atoms appeared at 63.0 ppm and 54.0 ppm respectively. From, DEPT 135 O-methylene and N-methylene carbons were confirmed by the signals at 63.0 and 54.0 respectively and two methylene carbons C3 and C4 were also confirmed by the signals at 32.6 and 21.5 respectively. The GC–MS spectrum exhibited the [M+H]+ peak at m/z 480. Thus, on the basis of above studies 8a has been assigned structure 1-[7-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-3-phenyl-propenone.

Microbiology

Antibacterial activity

All the synthesised compounds were screened in vitro for their antibacterial activity against two gram positive bacteria Staphylococcus aureus (ATCC-9144), Bacillus cereus (ATCC-11778) and two gram negative bacteria Escherichia coli (ATCC-8739), Proteus vulgaris (ATCC-29213) by the cup-plate agar diffusion method (Revol-Junelles et al., 1996) at different concentrations (50, 100, 150 and 200 μg/mL). Nutrient agar medium was used for the antibacterial screening. The Zone of inhibition (in mm) was compared with standard drug Streptomycin sulphate. The results are tabulated in Tables 4 and 5.

Table 4 Antibacterial activity of compounds 8a–j and 13a–j against two gram positive bacteria
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Table 5 Antibacterial activity of compounds 8a–j and 13a–j against two gram negative bacteria
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The investigation of antibacterial screening revealed that compounds 8a and 13a exhibited maximum zone of inhibition, indicates that compounds without substitutions on phenyl ring (benzaldehyde) showed prominent potency against all bacteria. compounds 8b–e, 8h, 8i, 13b–e, 13h, and 13i showed moderate zone of inhibition, indicate that compounds with substitutions at R1 and R2 positions on phenyl ring with electron donating groups enhances the antibacterial activity. Compounds with substitution at R1 position with OCH3 and Cl groups showed maximum zone of inhibition and compounds with substitution at R2 position with CH3, OCH3 and Cl groups showed maximum zone of inhibition. Compounds 8f, 8g, 8i, 13f, 13g, and 13i showed poor zone of inhibition against all bacterial strains, indicate that compounds with substitution at R2 position with N(CH3)2 and CH(CH3)2 groups diminishes the antibacterial potency.

Compounds 8a (14 mm), 8d (14 mm), 8e (13.5 mm) 13a (13 mm) and 13e (13 mm) showed maximum zone of inhibition compare with standard drug streptomycin (15 mm) against S. aureus. Compound 8e (13 mm) showed maximum potency compare with standard (16 mm) against B. cereus. Compounds 8a (14.5 mm), 8d (16 mm) and 8e (16 mm) showed high potency compare with standard (17 mm) against E. coli. Compounds 8a (13.5 mm) and 8d (14 mm) exhibited maximum inhibition compare with standard (16 mm) against P. vulgaris.

Antifungal activity

All the synthesised compounds were screened in vitro for their antifungal activity against Aspergillus Niger (ATCC-9029), Candida albicans (ATCC-2091) and Aspergillus foetidus (NCIM-505). Sabouraud’s agar medium was used for the antifungal screening. Zone of inhibition (in mm) was compared with standard drug Nystatin. The results are tabulated in Table 6.

Table 6 Antifungal activity of compounds 8a–j and 13a–j
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Antifungal activity studies revealed that the compounds 8a, 8d and 8e showed maximum zone of inhibition, compounds 8b, 8f, 8g, 13a, 13d, 13e and 13g showed moderate zone of inhibition and compounds 8c, 8h, 8i, 8j, 13b, 13c, 13f, 13h, 13i and 13j showed poor antifungal potency. This study indicates that compounds without substitution on phenyl ring showed maximum potency and compounds with substitutions with Cl, OCH3 and CH3 groups showed moderate zone of inhibition.

Compounds 8a, 8d, 8e, 13d and 13e exhibited maximum zone of inhibition against A. Niger. Compounds 8a, 8e, 8f and 13g showed maximum zone of inhibition against C. albicans. Compounds 8a and 8e showed maximum zone of inhibition against A. foetidus.

Biological assay

Antimicrobial activity

The test solutions of the samples were prepared in dimethylformamide (DMF). The antibiotics: Streptomycin sulphate was used as standard for antibacterial screening and Nystatin was used as a standard for antifungal screening. The antibacterial standard was dissolved in sterile-distilled water. The antifungal standard was dissolved in buffered 70 % propanol.

The microorganisms employed in this study were two gram positive bacteria such as S. aureus (ATCC-9144) and B. cereus (ATCC-11778) and two gram negative bacteria such as Escherichia coli (ATCC-8739) and P. vulgaris (ATCC-29213) and fungal strains like A. niger (ATCC-9029), Candica albicans (ATCC-2091) and A. foetidus (NCIM-505).

Nutrient broth (pH −7.2) was used for the preparation of inoculum of bacteria. Nutrient agar medium was used for the antibacterial screening, contained 20.0 g of agar in addition to the composition of nutrient broth. For antifungal screening, inoculum was prepared by transferring a loopful of fungal stock culture to 100 mL of conical flask containing 50 mL of Sabouraud’s broth. The composition of the broth was Glucose 40 g, Peptone 10 g, distilled water 1,000 mL. Sabouraud’s agar medium was used for the antifungal screening, contained 20.0 g of agar in addition to the composition of Sabouraud’s broth.

For antibacterial screening, the agar medium was sterilized by autoclaving at 120 °C for 15 min. The Petri plates and pipettes were sterilized by dry heat in a hot-air oven at 150 °C for 1 h. About 20 mL of the molten agar medium was poured in each of sterilized Petri plates and 0.5 mL of 24 h old broth cultures of bacterial strains were added to the respective Petri plates. The contents of the Petri plates were mixed thoroughly by rotary motion. After solidification of the medium, four cups (diameter 8 mm) were made with the help of a sterile borer at equal distances.

For antifungal activity, the corning sterile Petri plates were used for investigation. About 20 mL of the molten Sabouraud’s agar medium was poured in each of sterilized Petri plates and 0.5 mL of 24 h old broth cultures of fungal strains was added to the respective Petri plates. The contents of the Petri plates were mixed thoroughly by rotary motion. After solidification of the medium, four cups (diameter 8 mm) were made with the help of a sterile borer at equal distances.

Accurately measured 0.1 mL of four different concentrations (50, 100, 150 and 200 μg/mL) of test samples and 0.1 mL of four different concentrations of standard antibiotics (50, 100, 150 and 200 μg/mL) were added into the cups and labelled accordingly. The plates were kept undisturbed in a cool place for 1 h to allow the solutions to diffuse into the medium. The nutrient agar plates were then incubated at 37 °C for 24 h for antibacterial activity. For antifungal activity, the Sabouraud’s agar plates were then incubated at 28 °C for 48 h.

The presence of definite zone of inhibition surrounding the cups indicated antimicrobial activity. The diameter of the zone of inhibition was recorded. The experiments were performed, at least in triplicate.

Experimental

Materials

All the reagents and solvents were purchased from commercial sources. Analytical TLC was performed on Merck precoated 60 F254 silica gel plates. Visualization was done by exposing to iodine vapour and UV. IR spectra (υmax in cm−1) were recorded on a Shimadzu FT-IR 8400 S spectrometer. The melting points were taken in open capillary tubes on a Stuart SMP3 melting-point apparatus and are uncorrected. 1H, 13C NMR spectra were recorded in CDCl3 on a Bruker AVANCE-400 spectrometer using TMS as an internal standard. (Chemical shift in δ, ppm). Mass spectra were scanned on a shimadzu GCMS-QP 1000 spectrometer (shimadzu, Tokyo, Japan).

General procedures

Synthesis of 1-(2,2-dimethyl-7-prop-2-ynyloxy-chroman-6-yl)-ethanone (6)

Anhydrous K2CO3 (0.94 g, 6.80 mmol, 1.5 eq) was added to 1-(7-hydroxy-2,2-dimethyl-chroman-6-yl)-ethanone (1 g, 4.50 mmol, 1.0 eq) dissolved in 5 mL dry acetone. Propargyl bromide 80 % in toluene (0.64 g, 5.40 mmol, 1.2 eq) was added to the mixture. The reaction mixture was refluxed for about 8 h. After completion of the reaction (monitored by TLC), the solvent was removed under reduced pressure and added 30 mL ice cold water, then extracted with EtOAc and dried over anhydrous Na2SO4. Crude was purified by column chromatography using hexane/EtOAc (4:1) as eluent to give compound 6.

Pale yellow solid; m.p.: 60–62 °C; IR (KBr) cm−1: 3,294 (C≡C–H), 3,135 (Ar–H), 2,210 (C≡C), 1,648 (C=O), 1,226 (Ar–C), and 1,118 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.63 (s, 1H, Ar–H5), 6.42 (s, 1H, Ar–H8), 4.72 (d, 2H, O–CH2), 2.73 (t, J = 6.67 Hz, 2H, CH2), 2.60 (s, 3H, CH3), 2.54 (t, 1H, C≡C–H), 1.80 (t, J = 6.73 Hz, 2H, CH2), 1.36 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 197.7 (C=O), 159.0 (C8a), 157.3 (C7), 132.4 (C5), 120.8 (C6), 114.1 (C4a), 101.3 (C8), 77.9 (C2), 75.9 (C≡C–H), 75.7 (C≡C–H), 56.2 (O–CH2), 32.6 (C3), 32.0 (CH3), 26.8 (2×CH3), 21.4 (C4); MS [M+H]+: 259.

Synthesis of 1-[7-(1-benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl)-ethanone (7) using CuSO4·5H2O/Sodium ascorbate under conventional conditions

CuSO4·5H2O (0.05 g, 0.37 mmol) and sodium ascorbate (0.22 g, 1.10 mmol) were added to a mixture of Benzyl azide (1.0 g, 7.5 mmol) and 1-(2,2-dimethyl-7-prop-2-ynyloxy-chroman-6-yl)-ethanone (1.90 g, 7.50 mmol) 6 dissolved in t-BuOH:H2O (1:1, v/v) (5 mL) and was stirred under room temperature for 24 h. After completion of the reaction (monitored by TLC), the resulting mixture was poured into ice cold water (20 mL), extracted with 30 mL EtOAc, washed twice with saturated solution of NH4Cl, twice with brine and dried over Na2SO4. The organic layer was concentrated in vacuo and the residue was purified by column chromatography on silica gel eluted with hexane/EtOAc (2:1) to give compound 7.

Synthesis of 1-[7-(1-benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl)-ethanone (7) using CuSO4·5H2O/Sodium ascorbate under microwave irradiation

A mixture of Benzyl azide (1.0 g, 7.5 mmol), 1-(2,2-dimethyl-7-prop-2-ynyloxy-chroman-6-yl)-ethanone (1.90 g, 7.50 mmol) 6, CuSO4·5H2O (0.05 g, 0.37 mmol) and sodium ascarbate (0.22 g, 1.1 mmol) dissolved in t-BuOH:H2O (1:1, v/v) (5 mL) was subjected to microwave irradiation at 180 watts for 8–010 min. After completion of the reaction (monitored by TLC), the resulting mixture was poured into ice cold water (20 mL), extracted with 30 mL EtOAc, washed twice with saturated solution of NH4Cl, twice with brine and dried over Na2SO4. The organic layer was concentrated in vacuo and the residue was purified by column chromatography on silica gel eluted with hexane/EtOAc (2:1) to give compound 7.

Synthesis of 1-[7-(1-benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl)-ethanone (7) using CuI under conventional conditions

A mixture of Benzyl azide (1.0 g, 7.5 mmol), 1-(2,2-dimethyl-7-prop-2-ynyloxy-chroman-6-yl)-ethanone (1.90 g, 7.50 mmol) 6, triethylamine (0.90 g, 9.00 mmol) and CuI (0.14 g, 0.75 mmol) in DMF (5 mL) was stirred under room temperature for 24 h. After completion of the reaction (monitored by TLC), the resulting mixture was poured into ice cold water (20 mL), extracted with 30 mL EtOAc, washed twice with saturated solution of NH4Cl, twice with brine and dried over Na2SO4. The organic layer was concentrated in vacuo and the residue was purified by column chromatography on silica gel eluted with hexane/EtOAc (2:1) to give compound 7.

Synthesis of 1-[7-(1-benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl)-ethanone (7) using CuI under microwave irradiation

A mixture of Benzyl azide (1.0 g, 7.50 mmol), 1-(2,2-dimethyl-7-prop-2-ynyloxy-chroman-6-yl)-ethanone (1.90 g, 7.50 mmol) 6, triethylamine (0.90 g, 9.00 mmol) and CuI (0.14 g, 0.75 mmol) in DMF (5 mL) was subjected to microwave irradiation at 180 watts for 8–10 min. After completion of the reaction (monitored by TLC), the resulting mixture was poured into ice cold water (20 mL), extracted with 30 mL EtOAc, washed twice with saturated solution of NH4Cl, twice with brine and dried over Na2SO4. The organic layer was concentrated in vacuo and the residue was purified by column chromatography on silica gel eluted with hexane/EtOAc (2:1) to give compound 7.

White solid; m.p.: 95–97 °C; IR (KBr) cm−1: 3,138 (Ar–H), 1,648 (C=O), 1,455 (N=N), 1,226 (Ar–C), 1,182 (C–N) and 1,118 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.60 (s, 1H, Ar–H5), 7.53 (s, 1H, triazole-H), 7.42–7.35 (m, 3H, Ar–H), 7.28 (m, 2H, Ar–H), 6.44 (s, 1H, Ar–H8), 5.56 (s, 2H, O–CH2), 5.19 (s, 2H, N–CH2), 2.72 (t, J = 6.67 Hz, 2H, CH2), 2.45 (s, 3H, CH3), 1.79 (t, J = 6.73 Hz, 2H, CH2), 1.34 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 198.2 (C=O), 159.0 (C8a), 157.0 (C7), 144.1 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 134.5–124.1 (6C, Ar–C), 128.0 (C5), 123.4 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\) ), 127.5 (C5), 120.8 (C6), 114.1 (C4a), 101.3 (C8), 75.2, 67.1 (O–CH2), 54.2 (N–CH2), 31.9 (C3), 29.7 (CH3), 26.7 (2×CH3), 21.4 (C4); MS [M+H]+: 392.

1-(2,2-Dimethyl-7-prop-2-ynyloxy-chroman-6-yl)-3-tolyl-propenone (5c)

Pale yellow solid; m.p.:159–162 °C; IR (KBr) cm−1: 3,294 (C≡C–H), 3,138 (Ar–H), 2,210 (C≡C), 1,648 (C=O), 1,615 (C=C), 1,226 (Ar–C), and 1,118 (Ar–O). 1H NMR (400 MHz, CDCl3): 7.68–7.64 (d, 1H, J = 15.76 Hz, Hβ), 7.58–7.55 (m, 2H, Hα, Ar–H5), 7.52–7.51 (m, 2H, Ar–H), 7.18–7.17 (d, 2H, J = 7.68 Hz, Ar–H), 6.45 (s, 1H, Ar–H8), 4.71 (s, 2H, O–CH2), 2.74 (t, J = 6.67 Hz, 2H, CH2), 2.53 (s, 1H, C≡C–H), 2.36 (s, 3H, CH3−), 1.81 (t, J = 6.73 Hz, 2H, CH2), 1.35 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 191.2 (C=O), 158.6 (C8a), 156.6 (C7), 141.1 (HC=CH), 132.8 (C5), 132.7–127.0 (6C, Ar–C), 122.0 (HC=CH), 114.1 (C4a), 109.8 (C6), 101.3 (C8), 78.1 (C2), 75.9 (C≡C–H), 75.7 (C≡C–H), 56.2 (O–CH2), 32.6 (C3), 32.7 (CH3), 26.9 (2×CH3), 21.4 (C4); MS [M+H]+: 361.

1-(2,2-Dimethyl-5-prop-2-ynyloxy-chroman-6-yl)-3-tolyl-propenone (10c)

Pale yellow solid; m.p.: 59–62 °C; IR (KBr) cm−1: 3,294 (C≡C–H), 3,138 (Ar–H), 2,210 (C≡C), 1,648 (C=O), 1,615 (C=C), 1,226 (Ar–C), and 1,118 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.63 (d, 1H, J = 15.76 Hz, Hβ), 7.58–7.51 (m, 4H, Ar–H5, Ar–H), 7.18–7.12 (d, 2H, J = 7.68 Hz, Ar–H), 6.45 (s, 1H, Ar–H8), 4.71 (s, 2H, O–CH2), 2.74 (t, J = 6.67 Hz, 2H, CH2), 2.53 (s, 1H, C≡C–H), 2.36 (s, 3H, CH3−), 1.81 (t, J = 6.73 Hz, 2H, CH2), 1.35 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 191.3 (C=O), 159.0 (C8a), 157.3 (C5), 143.6 (HC=CH), 137.3–126.6 (6C, Ar–C), 124.7 (C7), 115.9 (HC=CH), 113.9 (C6), 109.9 (C4a), 107.0 (C8), 77.9 (C2), 75.9 (C≡C–H), 75.7 (C≡C–H), 63.2 (O–CH2), 32.0 (C3), 26.7 (2×CH3), 20.9 (CH3), 17.5 (C4); MS [M+H]+: 361.

1-(2,2-Dimethyl-5-prop-2-ynyloxy-chroman-6-yl)-ethanone (11)

Pale yellow solid; m.p.: 60–62 °C; IR (KBr) cm−1: 3,294 (C≡C–H), 3,135 (Ar–H), 2,210 (C≡C), 1,648 (C=O), 1,226 (Ar–C), and 1,118 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.63 (d, J = 8.78 Hz, 1H, Ar–H7), 6.42 (d, J = 8.78 Hz, 1H, Ar–H8), 4.73 (d, 2H, O–CH2), 2.73 (t, J = 6.67 Hz, 2H, CH2), 2.60 (s, 3H, CH3), 2.55 (t, 1H, C≡C–H), 1.80 (t, J = 6.73 Hz, 2H, CH2), 1.36 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 197.7 (C=O), 159.0 (C8a), 157.3 (C5), 127.6 (C7), 109.3 (C4a), 108.9 (C8), 102.8 (C6), 77.9 (C2), 75.9 (C≡C–H), 75.7 (C≡C–H), 56.2 (O–CH2), 32.6 (C3), 32.0 (CH3), 26.8 (2×CH3), 17.5 (C4); MS [M+H]+: 259.

1-[5-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-ethanone (12)

White solid, m.p.: 95–98 °C; IR (KBr) cm−1: 3,138 (Ar–H), 1,648 (C=O), 1,455 (N=N), 1,226 (Ar–C), 1,182 (C–N) and 1,118 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.62 (s, 1H, triazole-H), 7.54–7.51 (d, J = 8.78 Hz, 1H, Ar–H7), 7.45–7.37 (m, 4H, Ar–H), 7.28 (m, 1H, Ar–H), 6.63–6.60 (d, J = 8.78 Hz, 1H, Ar–H), 5.54 (s, 2H, O–CH2), 5.02 (s, 2H, N–CH2), 2.77 (t, J = 6.67 Hz, 2H, CH2), 2.54 (s, 3H, CH3), 1.74 (t, J = 6.73 Hz, 2H, CH2), 1.34 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 198.2 (C=O), 159.0 (C8a), 157.0 (C5), 144.1 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\) ), 134.5–128.1 (6C, Ar–C), 128.7 (C7), 124.1 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 116.4 (C4a), 113.6 (C8), 102.8 (C6), 75.2 (C2), 67.1 (O–CH2), 54.2 (N–CH2), 31.9 (C3), 29.7 (CH3), 26.7 (2×CH3), 17.4 (C4); MS [M+H]+: 392.

Synthesis of 1-[7-(1-benzyl-1H-[1,2,3]triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-3-phenyl-propenone (8)

To a mixture of 1-[7-(1-benzyl-1H-[1,2,3]triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-ethanone (0.1 g, 0.25 mmol) 7 and aryl aldehydes (0.25 mmol, 1 eq) 3a–j in EtOH (5 mL), pellets of KOH (0.01 g, 1.2 eq) was added and subjected to microwave irradiation at 180 watts 2-4 min. The progress of the reaction was monitored by TLC. After completion of reaction, it was poured into crushed ice, carefully neutralized with 3 N HCl and extracted with EtOAc (15 mL). The organic layer was concentrated in vacuo and purified by column chromatography on silica gel eluted with hexane/EtOAc (3:1) to give compound 8.

1-[7-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-3-phenyl-propenone (8a)

Pale yellow solid; m.p.: 130–132 °C; IR (KBr) cm−1: 3,138 (Ar–H), 1,648 (C=O), 1,615 (C=C), 1,455 (N=N), 1,226 (Ar–C), 1,182 (C–N) and 1,118 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 8.29 (s, 1H, Ar–H5), 8.16–8.11 (d, 1H, J = 15.96 Hz, Hβ), 7.79–7.51 (m, 7H, Hα, Ar–H), 7.20–7.12 (m, 3H, Ar–H), 7.11–7.09 (m, 2H, Ar–H), 6.51 (s, 1H, Ar–H8), 5.41 (s, 2H, O–CH2), 5.21 (s, 2H, N–CH2), 2.76 (t, J = 7.02 Hz, 2H, CH2), 1.83 (t, J = 7.02 Hz, 2H, CH2), 1.37 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 190.9 (C=O), 160.5 (C8a), 158.9 (C7), 143.6 (HC=CH), 142.6 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 135.1–124.7 (12C, Ar–C), 130.2 (C5), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 118.7 (HC=CH), 115.9 (C4a), 110.9 (C6), 100.8 (C8), 75.2 (C2), 63.2 (O–CH2), 54.0 (N–CH2), 32.0 (C3), 26.7 (2×CH3), 21.8 (C4); MS [M+H]+: 480.

1-[7-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-3-p-tolyl-propenone (8b)

Pale yellow solid; m.p.: 155–157 °C; IR (KBr) cm−1: 3,133 (Ar–H), 1,649 (C=O), 1,613 (C=C), 1,455 (N=N), 1,231 (Ar–C), 1,141 (C–N) and 1,117 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.60 (m, 3H, J = 17.13 Hz, Hβ, Ar–H), 7.51 (s, 1H, Ar–H5), 7.45–7.30 (m, 5H, Ar–H), 7.18 (m, 2H, Ar–H), 7.0 (d, 2H, Ar–H), 6.51 (s, 1H, Ar–H8), 5.20 (s, 4H, O–CH2, N–CH2), 2.77 (t, J = 6.67 Hz, 2H, CH2), 2.40 (s, 1H, CH3), 1.83 (t, J = 6.73 Hz, 2H, CH2), 1.38 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 190.9 (C=O), 160.5 (C8a), 158.9 (C7), 143.6 (HC=CH), 142.4 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 137.6–126.9 (12C, Ar–C), 130.2 (C5), 122.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 121.7 (HC=CH), 115.9 (C4a), 110.9 (C7), 101.2 (C8), 75.2 (C2), 63.1 (O–CH2), 54.0 (N–CH2), 32.7 (C3), 26.8 (2×CH3), 22.4 (C4), 21.5 (CH3); MS [M+H]+: 494.

1-[7-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-3-(4-methoxy-phenyl-propenone (8c)

Pale yellow solid; m.p.: 133–135 °C; IR (KBr) cm−1: 3,135 (Ar–H), 1,649 (C=O), 1,616 (C=C), 1,459 (N=N), 1,255 (Ar–C), 1,145 (C–N) and 1,118 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.53–7.51 (m, 2H, Hβ, Ar–H5), 7.41–7.31 (m, 4H, Hα, Ar–H), 7.10–7.07 (m, 2H, Ar–H), 6.91 (d, 2H, Ar–H), 6.46 (s, 1H, Ar–H8), 5.33 (d, 2H, O–CH2), 4.96 (d, 2H, N–CH2), 3.86 (s, 1H, OCH3), 2.75 (t, J = 6.67 Hz, 2H, CH2), 1.82 (t, J = 6.73 Hz, 2H, CH2), 1.36 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 190.3 (C=O), 160.5 (C8a), 159.8 (1C, Ar–C), 158.9 (C7), 143.6 (HC=CH), 142.6 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 135.1–124.7 (9C, Ar–C), 130.2 (C5), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 118.7 (HC=CH), 115.9 (C4a), 114.5 (2C, Ar–C), 110.9 (C6), 100.8 (C8), 75.2 (C2), 63.0 (O–CH2), 56.5 (N–CH2), 54.8 (O–CH3), 32.0 (C3), 26.7 (2×CH3), 21.8 (C4). MS [M+H]+: 510.

1-[7-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-3-(3,4-dimethoxy-phenyl)-propenone (8d)

Pale yellow solid; m.p.: 122–124 °C; IR (KBr) cm−1: 3,064 (Ar–H), 1,668 (C=O), 1,606 (C=C), 1,461 (N=N), 1,265 (Ar–C), 1,141 (C–N) and 1,119 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.61–7.54 (m, 3H, Hβ, Ar–H5, Ar–H), 7.43–7.38 (m, 3H, Ar–H), 7.24–7.23 (m, 4H, Hα, Ar–H), 7.11–7.01 (m, 3H, Ar–H), 6.88–6.85 (d, J = 8.16 Hz, 1H, Ar–H), 6.47 (s, 1H, Ar–H8), 5.25 (s, 2H, O–CH2), 5.20 (s, 2H, N–CH2), 3.92 (d, J = 17.37 Hz, 6H, 2×CH3), 2.74 (t, J = 6.79 Hz, 2H, CH2), 1.82 (t, J = 6.79 Hz, 2H, CH2), 1.34 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 190.3 (C=O), 160.5 (C8a), 158.9 (C7), 149.3 (2C, Ar–C), 143.6 (HC=CH), 142.6 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 135.1–124.7 (8C, Ar–C), 130.2 (C5), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 118.7 (HC=CH), 115.9 (C4a), 112.5 (2C, Ar–C), 110.9 (C6), 100.8 (C8), 75.2 (C2), 63.2 (O–CH2), 56.5 (N–CH2), 54.8 (2×O–CH3), 32.0 (C3), 26.7 (2×CH3), 21.8 (C4); MS [M+H]+: 540.

1-[7-(1-Benzyl-1 H-[1,2,3] triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-3-(3,4,5-trimethoxy-phenyl)-propenone (8e)

Pale yellow solid; m.p.: 70–72 °C; IR (KBr) cm−1: 3,138 (Ar–H), 1,653 (C=O), 1,615 (C=C), 1,455 (N=N), 1,279 (Ar–C), 1,182 (C–N) and 1,118 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.56 (s, 1H, Ar–H5), 7.51 (s, 1H, Ar–H), 7.46–7.40 (d, J = 15.86 Hz, 1H, Hβ), 7.38 (s, 1H, Ar–H), 7.28–7.21 (m, 3H, Hα, Ar–H), 7.03–7.00 (dd, 1H, Ar–H), 6.75 (s, 2H, Ar–H), 6.47 (s, 1H, Ar–H8), 5.26 (s, 2H, O–CH2), 5.19 (s, 2H, N–CH2), 3.88 (s, 3H, 1×O–CH3), 3.85 (s, 6H, 2×O–CH3), 2.76 (t, J = 6.78 Hz, 2H, CH2), 1.82 (t, J = 6.13 Hz, 2H, CH2), 1.36 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 190.9 (C=O), 171.2 (C8a), 158.9 (C7), 156.9 (2C, Ar–C), 143.6 (HC=CH), 142.6 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 135.1–125.4 (7C, Ar–C), 130.2 (C5), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 118.7 (HC=CH), 115.9 (C4a), 110.9 (C6), 104.3 (2C, Ar–C), 100.8 (C8), 75.7 (C2), 63.2 (O–CH2), 60.9 (1×O–CH3), 56.2 (N–CH2), 56.0 (2×O–CH3), 32.0 (C3), 26.7 (2×CH3), 21.8 (C4); MS [M+H]+:570.

1-[7-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-3-(4-dimethylamino-phenyl)-propenone (8f)

Yellow solid; m.p.: 113–115 °C; IR (KBr) cm−1: 3,137 (Ar–H), 1,647 (C=O), 1,606 (C=C), 1,491 (N=N), 1,275 (Ar–C), 1,140 (C–N) and 1,116 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.64–7.60 (d, J = 15.99 Hz, 1H, Hβ), 7.54 (s, 1H, Ar–H5), 7.42–7.40 (m, 3H, Ar–H), 7.34–7.26 (m, 4H, Hα, Ar–H), 7.04–7.02 (d, J = 6.99 Hz, 2H, Ar–H), 6.69–6.67 (d, J = 7.99 Hz, 2H, Ar–H), 6.47 (s, 1H, Ar–H8), 5.22 (s, 4H, O–CH2, N–CH2), 3.03 (s, 6H, 2×CH3), 2.77 (t, J = 6.99 Hz, 2H, CH2), 1.83 (t, J = 6.99 Hz, 2H, CH2), 1.38 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 191.4 (C=O), 159.1 (C8a), 158.2 (C7), 151.9 (1C, Ar–C), 144.0 (HC=CH), 143.8 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 135.1–125.4 (9C, Ar–C), 130.2 (C5), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 118.7 (HC=CH), 115.9 (C4a), 112.7 (2C, Ar–C), 110.9 (C6), 100.8 (C8), 75.7 (C2), 63.2 (O–CH2), 56.2 (N–CH2), 40.1 (2×N–CH3), 32.0 (C3), 26.7 (2×CH3), 21.8 (C4); MS [M+H]+: 523.

1-[7-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-3-(4-chloro-phenyl)-propenone (8g)

Pale yellow solid; m.p.: 152–154 °C; IR (KBr) cm−1: 3,136 (Ar–H), 1,653 (C=O), 1,569 (C=C), 1,491 (N=N), 1,281 (Ar–C), 1,142 (C–N) and 1,118 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.60–7.54 (m, 3H, Hβ, Ar–H5), 7.39–7.30 (m, 8H, Hα, Ar–H), 7.08–7.06 (dd, 2H, Ar–H), 6.49 (s, 1H, Ar–H8), 5.32 (s, 2H, O–CH2), 5.19 (s, 2H, N–CH2), 2.76 (t, J = 7.02 Hz, 2H, CH2), 1.82 (t, J = 7.02 Hz, 2H, CH2), 1.36 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 190.5 (C=O), 171.1 (C8a), 159.1 (C7), 143.6 (HC=CH), 141.1 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 135.1–124.7 (12C, Ar–C), 130.2 (C5), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 118.7 (HC=CH), 115.9 (C4a), 110.9 (C6), 100.8 (C8), 75.2 (C2), 63.0 (O–CH2), 54.1 (N–CH2), 32.0 (C3), 26.8 (2×CH3), 21.1 (C4); MS [M+H]+: 514.

1-[7-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-3-(3,4-dichloro-phenyl)-propenone (8h)

Pale yellow solid; m.p.: 95–97 °C; IR (KBr) cm−1: 3,139 (Ar–H), 1,660 (C=O), 1,568 (C=C), 1,491 (N=N), 1,287 (Ar–C), 1,157 (C–N) and 1,109 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.61 (s, 1H, Ar–H5),7.55–7.54 (d, J = 15.99 Hz, 2H, Hβ, Ar–H), 7.49–7.41 (m, 3H, Hα, Ar–H), 7.31–7.29 (m, 4H, Ar–H), 7.13–7.11 (d, J = 6.99 Hz, 2H, Ar–H), 6.49 (s, 1H, Ar–H8), 5.40 (s, 2H, O–CH2), 5.21 (s, 2H, N–CH2), 2.77 (t, J = 6.99 Hz, 2H, CH2), 1.84 (t, J = 6.99 Hz, 2H, CH2), 1.38 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 197.1 (C=O), 171.1 (C8a), 159.2 (C7), 143.5 (HC=CH), 141.0 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 135.2–124.7 (12C, Ar–C), 130.8 (C5), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 118.7 (HC=CH), 115.9 (C4a), 110.9 (C6), 100.8 (C8), 75.3 (C2), 63.2 (O–CH2), 54.1 (N–CH2), 31.9 (C3), 26.7 (2×CH3), 21.1 (C4); MS [M+H]+:549.

1-[7-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-3-(4-isopropyl-phenyl)-propenone (8i)

Pale yellow solid; m.p.: 115–117 °C; IR (KBr) cm−1: 3,135 (Ar–H), 1,665 (C=O), 1,609 (C=C), 1,468 (N=N), 1,211 (Ar–C), 1,176 (C–N) and 1,121 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.59–7.52 (m, 2H, Hβ, Ar–H5), 7.46–7.43 (d, J = 15.86 Hz, 1H, Hα), 7.40–7.36 (m, 4H, Ar–H), 7.26–7.20 (m, 4H, Ar–H), 6.98–6.95 (dd, 2H, Ar–H), 6.46 (s, 1H, Ar–H8), 5.20 (s, 2H, O–CH2), 5.17 (s, 2H, N–CH2), 2.98–2.89 (m, 1H, C–H), 2.76 (t, J = 6.67 Hz, 2H, CH2), 1.82 (t, J = 6.67 Hz, 2H, CH2), 1.36 (s, 6H, 2×CH3), 1.27 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 190.2 (C=O), 163.2 (C8a), 158.8 (C7), 150.5 (1C, Ar–C), 143.6 (HC=CH), 142.9 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 135.1–124.7 (11C, Ar–C), 130.2 (C5), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 118.7 (HC=CH), 115.9 (C4a), 110.9 (C6), 100.8 (C8), 75.2 (C2), 63.2 (O–CH2), 53.9 (N–CH2), 34.1 (CH–2×CH3), 32.0 (C3), 26.8 (2×CH3), 23.8 (CH–2×CH3), 21.1 (C4); MS [M+H]+: 522.

1-[7-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy-2,2-dimethyl-chroman-6-yl]-3-(3-nitro-phenyl)-propenone (8j)

Pale yellow solid; m.p.: 100–102 °C; IR (KBr) cm−1: 3,140 (Ar–H), 1,653 (C=O), 1,615 (C=C), 1,455 (N=N), 1,279 (Ar–C), 1,182 (C–N) and 1,118 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.80–7.75 (m, 2H, Ar–H), 7.54–7.52 (d, J = 16.30 Hz, 1H, Hβ), 7.46 (s, 1H, Ar–H5), 7.43–7.31 (m, 4H, Hα, Ar–H), 7.21–7.15 (m, 2H, Ar–H), 7.11–7.08 (d, 1H, Ar–H), 6.98–9.95 (m, 2H, Ar–H), 6.46 (s, 1H, Ar–H8), 5.20 (s, 2H, O–CH2), 5.17 (s, 2H, N–CH2), 2.76 (t, J = 6.67 Hz, 2H, CH2), 1.82 (t, J = 6.73 Hz, 2H, CH2), 1.36 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 189.9 (C=O), 163.2 (C8a), 159.4 (C7), 148.6 (1C, Ar–C), 143.6 (HC=CH), 142.9 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 139.6–124.7 (11C, Ar–C), 130.2 (C5), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 118.7 (HC=CH), 115.9 (C4a), 110.9 (C6), 100.8 (C8), 75.2 (C2), 63.0 (O–CH2), 53.9 (N–CH2), 32.0 (C3), 26.8 (2×CH3), 21.1 (C4); MS [M+H]+: 525.

1-[5-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-3-phenyl-propenone (13a)

White solid; m.p.: 98–100 °C; IR (KBr) cm−1: 3,139 (Ar–H), 1,661 (C=O), 1,594 (C=C), 1,453 (N=N), 1,226 (Ar–C), 1,165 (C–N) and 1,119 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.71–7.67 (d, 2H, Hβ, Ar–H7,), 7.58–7.53 (m, 4H, Hα, Ar–H), 7.40 (m, 4H, Ar–H), 7.26 (m, 2H, Ar–H), 7.10–7.07 (d, 2H, Ar–H), 6.68–6.65 (d, J = 9.09 Hz, 1H, Ar–H8), 5.31 (s, 2H, O–CH2), 4.96 (s, 2H, N–CH2), 2.80 (t, J = 7.02 Hz, 2H, CH2), 1.76 (t, J = 7.02 Hz, 2H, CH2), 1.33 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 190.9 (C=O), 158.9 (C8a), 157.1 (C5), 143.6 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 142.6 (HC=CH), 135.1–126.6 (12C, Ar–C), 124.7 (C7), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 115.9 (HC=CH), 113.9 (C6), 109.9 (C4a), 107.0 (C8), 75.2 (C2), 67.7 (O–CH2), 54.0 (N–CH2), 32.0 (C3), 26.7 (2×CH3), 17.5 (C4); MS [M+H]+: 480.

1-[5-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-3-p-tolyl-propenone (13b)

Pale yellow solid; m.p.: 98–100 °C; IR (KBr) cm−1: 3,152 (Ar–H), 1,645 (C=O), 1,592 (C=C), 1,495 (N=N), 1,222 (Ar–C), 1,164 (C–N) and 1,118 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.70 (d, J = 15.67 Hz, 1H, Hβ), 7.65–7.45 (m, 5H, Ar–H7, Hα, Ar–H), 7.33–7.32 (m, 3H, Ar–H), 7.20–7.17 (d, J = 8.10 Hz, 2H, Ar–H), 7.09–7.08 (m, 2H, Ar–H), 6.69–6.66 (d, J = 8.87 Hz, 1H, Ar–H8), 5.32 (s, 2H, O–CH2), 4.96 (s, 2H, N–CH2), 2.81 (t, J = 6.06 Hz, 2H, CH2), 2.3 (s, 1H, CH3), 1.8 (t, J = 6.67 Hz, 2H, CH2), 1.33 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 190.9 (C=O), 160.5 (C8a), 158.9 (C5), 143.6 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 142.6 (HC=CH), 137.3–126.6 (12C, Ar–C), 124.7 (C7), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 115.9 (HC=CH), 113.9 (C6), 109.9 (C4a), 107.0 (C8), 75.2 (C2), 67.8 (O–CH2), 54.0 (N–CH2), 32.0 (C3), 26.7 (2×CH3), 21.3 (CH3), 17.5 (C4); MS [M+H]+: 494.

1-[5-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-3-(4-methoxy-phenyl)-propenone (13c)

Pale yellow solid; m.p.: 90–92 °C; IR (KBr) cm−1: 3,140 (Ar–H), 1,649 (C=O), 1,605 (C=C), 1,485 (N=N), 1,221 (Ar–C), 1,172 (C–N) and 1,108 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.67 (d, 1H, Ar–H7), 7.55 (dd, J = 12.16 Hz, 1H, Hβ), 7.40 (d, J = 6.74 Hz, Ar–H), 7.29 (m, Ar–H), 7.08 (dd, J = 12.27 Hz, 1H, Hα), 6.7 (d, 1H, Ar–H8), 5.31 (s, 2H, O–CH2), 5.21 (s, 2H, N–CH2), 2.81 (t, J = 6.67 Hz, 2H, CH2), 1.76 (t, J = 6.66 Hz, 2H, CH2), 1.33 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 190.3 (C=O), 160.5 (C8a), 158.9 (C5), 157.2 (1C, Ar–C), 143.6 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 142.6 (HC=CH), 134.3–126.6 (9C, Ar–C), 124.7 (C7), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 115.9 (HC=CH), 114.8 (2C, Ar–C), 113.9 (C6), 109.9 (C4a), 107.0 (C8), 75.2 (C2), 67.2 (O–CH2), 54.0 (N–CH2), 52.8 (O–CH3), 32.0 (C3), 26.7 (2×CH3), 17.5 (C4); MS [M+H]+: 510.

1-[5-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-3-(3,4-dimethoxy-phenyl)-propenone (13d)

White solid; m.p.: 92–95 °C; IR (KBr) cm−1: 3,050 (Ar–H), 1,658 (C=O), 1,611 (C=C), 1,476 (N=N), 1,227 (Ar–C), 1,180 (C–N) and 1,121 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.66–7.62 (d, J = 16.06 Hz, 1H, Hβ), 7.55–7.53 (d, J = 9.03 Hz, 1H, Ar–H7), 7.51–7.26 (m, 3H, Hα, Ar–H), 7.10–6.86 (m, 5H, Ar–H), 6.84–6.67 (d, 1H, Ar–H), 6.64–6.63 (d, J = 9.03 Hz, 1H, Ar–H8), 5.34 (s, 2H, O–CH2), 5.02 (s, 2H, N–CH2), 3.88 (s, 6H, 2×CH3), 2.80 (t, J = 7.02 Hz, 2H, CH2), 1.76 (t, J = 7.02 Hz, 2H, CH2), 1.30 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 190.3 (C=O), 160.5 (C8a), 158.9 (C5), 150.1 (2C, Ar–C), 143.6 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 142.6 (HC=CH), 134.3–125.2 (8C, Ar–C), 124.7 (C7), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 115.9 (HC=CH), 113.9 (C6), 111.8 (2C, Ar–C), 109.9 (C4a), 107.0 (C8), 75.2 (C2), 67.7 (O–CH2), 54.0 (N–CH2), 52.8 (2×O–CH3), 32.0 (C3), 26.7 (2×CH3), 17.5 (C4); MS [M+H]+: 540.

1-[5-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-3–(3,4,5-trimethoxy-phenyl)-propenone (13e)

Pale yellow solid; m.p.: 93–95 °C; IR (KBr) cm−1: 3,137 (Ar–H), 1,659 (C=O), 1,592 (C=C), 1,503 (N=N), 1,235 (Ar–C), 1,162 (C–N) and 1,124 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.61–7.57 (d, J = 16.06 Hz, 1H, Hβ), 7.54–7.53 (d, J = 8.78 Hz, 1H, Ar–H7), 7.45–7.31 (m, 7H, Hα, Ar–H), 6.78 (s, 2H, Ar–H), 6.67–6.65 (d, J = 8.78 Hz, 1H, Ar–H8), 5.34 (s, 2H, O–CH2), 4.97 (s, 2H, N–CH2), 3.91 (s, 9H, 3×CH3), 2.80 (t, J = 7.27 Hz, 2H, CH2), 1.83 (t, J = 7.02 Hz, 2H, CH2), 1.32 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 190.9 (C=O), 158.8 (C8a), 156.9 (C5), 153.5 (2C, Ar–C), 143.6 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 142.6 (HC=CH), 134.3–125.9 (8C, Ar–C), 124.7 (C7), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 115.9 (HC=CH), 113.9 (C6), 109.9 (C4a), 107.0 (C8), 105.6 (2C, Ar–C), 75.1 (C2), 67.7 (O–CH2), 60.8 (1×O–CH3), 56.2 (2×O–CH3), 54.0 (N–CH2), 32.0 (C3), 26.7 (2×CH3), 17.5 (C4); MS [M+H]+: 570.

1-[5-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-3-(4-dimethylamino-phenyl)-propenone (13f)

Yellow solid; m.p.: 95–97 °C; IR (KBr) cm−1: 3,136 (Ar–H), 1,646 (C=O), 1,594 (C=C), 1,476 (N=N), 1,227 (Ar–C), 1,165 (C–N) and 1,118 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.69–7.65 (d, J = 15.81 Hz, 1H, Hβ), 7.51–7.46 (m, 3H, Ar–H7, Ar–H), 7.34–7.28 (m, 5H, Ar–H), 7.08–7.06 (m, 2H, Ar–H), 6.68–6.63 (m, 3H, Ar–H8, Ar–H), 5.31 (s, 2H, O–CH2), 4.98 (s, 2H, N–CH2), 3.10 (s, 6H, 2×CH3), 2.81 (t, J = 7.27 Hz, 2H, CH2), 1.76 (t, J = 7.02 Hz, 2H, CH2), 1.33 (s, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 191.4 (C=O), 158.2 (C8a), 156.5 (C5), 151.9 (1C, Ar–C), 144.0 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 143.8 (HC=CH), 134.5–125.4 (9C, Ar–C), 124.7 (C7), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 115.7 (HC=CH), 113.9 (C6), 111.3 (2C, Ar–C), 109.9 (C4a), 107.0 (C8), 74.9 (C2), 67.5 (O–CH2), 53.9 (N–CH2), 40.1 (2×N–CH3), 32.0 (C3), 26.7 (2×CH3), 17.5 (C4); MS [M+H]+: 523.

1-[5-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-3-(4-chloro-phenyl)-propenone (13g)

Pale yellow solid; m.p.: 150–152 °C; IR (KBr) cm−1: 3,150 (Ar–H), 1,648 (C=O), 1,591 (C=C), 1,486 (N=N), 1,216 (Ar–C), 1,165 (C–N) and 1,120 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.64–7.60 (d, J = 16.06 Hz, 1H, Hβ), 7.56–7.46 (m, 4H, Hα, Ar–H7, Ar–H),7.35–7.31(m, 5H, Ar–H), 7.24 (d, J = 9.78 Hz, 1H, Ar–H), 7.14–7.11 (m, 2H, Ar–H), 6.67–6.65 (d, J = 8.53 Hz, 1H, Ar–H8), 5.37 (s, 2H, O–CH2), 4.95 (s, 2H, N–CH2), 2.79 (t, J = 7.02 Hz, 2H, CH2), 1.77 (t, J = 7.02 Hz, 2H, CH2), 1.33 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 190.5 (C=O), 171.1 (C8a), 159.0 (C5), 143.6 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 141.1 (HC=CH), 134.3–126.6 (12C, Ar–C), 124.7 (C7), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 115.9 (HC=CH), 114.0 (C6), 109.9 (C4a), 107.0 (C8), 75.2 (C2), 67.8 (O–CH2), 54.0 (N–CH2), 31.9 (C3), 26.7 (2×CH3), 17.5 (C4); MS [M+H]+: 514.

1-[5-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-3-(3,4-dichloro-phenyl)-propenone (13h)

Pale yellow solid; m.p.: 97–99 °C; IR (KBr) cm−1: 3,140 (Ar–H), 1,644 (C=O), 1,593 (C=C), 1,467 (N=N), 1,220 (Ar–C), 1,169 (C–N) and 1,118 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.84–7.82 (d, J = 8.78 Hz, 1H, Ar–H7), 7.68–7.63 (d, J = 15.05 Hz, 1H, Hβ), 7.61–7.50(m, 2H, Ar–H), 7.42–7.33 (m, 7H, Hα, Ar–H), 7.15–7.13 (m, 2H, Ar–H), 6.68–6.65 (d, J = 8.78 Hz, 1H, Ar–H8), 5.41 (s, 2H, O–CH2), 4.96 (s, 2H, N–CH2), 2.80 (t, J = 7.02 Hz, 2H, CH2), 1.77 (t, J = 7.02 Hz, 2H, CH2), 1.33 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 197.1 (C=O), 171.1 (C8a), 159.2 (C5), 143.5 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 139.7 (HC=CH), 135.2–127.7 (12C, Ar–C), 124.7 (C7), 123.6 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 115.9 (HC=CH), 113.9 (C6), 109.9 (C4a), 107.0 (C8), 75.2 (C2), 67.8 (O–CH2), 54.1 (N–CH2), 34.8 (C3), 26.7 (2×CH3), 17.5 (C4); MS [M+H]+: 549.

1-[5-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-3-(4-isopropyl-phenyl)-propenone (13i)

Pale yellow solid; m.p.: 95–97 °C; IR (KBr) cm−1: 3,146 (Ar–H), 1,667 (C=O), 1,611 (C=C), 1,475 (N=N), 1,229 (Ar–C), 1,186 (C–N) and 1,098 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 7.70–7.66 (d, J = 16.06 Hz, 1H, Hβ), 7.54–7.46 (m, 5H, Ar–H7, Ar–H), 7.35–7.29 (m, 5H, Hα, Ar–H), 7.08–7.06 (m, 2H, Ar–H), 6.67–6.64 (d, J = 8.78 Hz, 1H, Ar–H8), 5.30 (s, 2H, O–CH2), 4.97 (s, 2H, N–CH2), 2.9 (m, 1H, C–H), 2.80 (t, J = 7.02 Hz, 2H, CH2),1.76 (t, J = 7.02 Hz, 2H, CH2), 1.33 (s, 6H, 2×CH3), 1.26 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 191.2 (C=O), 158.8 (C8a), 156.9 (C5), 151.7 (1C, Ar–C), 143.6 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 142.6 (HC=CH), 134.4–125.6 (11C, Ar–C), 124.8 (C7), 123.8 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 115.9 (HC=CH), 113.9 (C6), 109.9 (C4a), 107.0 (C8), 75.1 (C2), 67.6 (O–CH2), 53.9 (N–CH2), 34.1 (CH–2×CH3), 32.0 (C3), 26.7 (2×CH3), 23.8 (CH–2×CH3), 17.5 (C4); MS [M+H]+: 522.

1-[5-(1-Benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-3-(3-nitro-phenyl-propenone (13j)

Pale yellow solid; m.p.: 80–83 °C; IR (KBr) cm−1: 3,140 (Ar–H), 1,655 (C=O), 1,617 (C=C), 1,493 (N=N), 1,283 (Ar–C), 1,142 (C–N) and 1,115 (Ar–O); 1H NMR (400 MHz, CDCl3) δ (ppm): 8.38–8.36 (t, 1H, Ar–H), 8.22–8.19 (m, 1H, Ar–H), 7.85–7.83 (dd, 1H, Ar–H), 7.66–7.65(d, J = 16.30 Hz, 1H, Hβ), 7.58–7.56 (d, J = 8.78 Hz, 1H, Ar–H7), 7.54–7.52 (d, J = 16.30 Hz, Hα),7.39 (s, 1H, Ar–H), 7.37–7.33 (m, 4H, Ar–H), 7.18–7.16 (m, 2H, Ar–H), 6.69–6.67 (d, J = 8.78 Hz, 1H, Ar–H8), 5.44 (s, 2H, O–CH2), 5.00 (s, 2H, N–CH2), 2.78 (t, J = 7.02 Hz, 2H, CH2), 1.18 (t, J = 6.67 Hz, 2H, CH2), 1.34 (s, 6H, 2×CH3); 13C NMR (100 MHz, CDCl3) δ (ppm): 189.9 (C=O), 159.4 (C8a), 157.3 (C5), 148.6 (1C, Ar–C), 143.5 (1,2,3-triazole \({\text{C}}_{{ 4^{\prime } }}\)), 139.6 (HC=CH), 136.9–124.2 (11C, Ar–C), 123.2 (C7), 122.3 (1,2,3-triazole \({\text{C}}_{{ 5^{\prime } }}\)), 115.9 (HC=CH), 114.1 (C4a), 110.9 (C6), 100.8 (C8), 75.3 (C2), 67.9 (O–CH2), 54.1 (N–CH2), 31.9 (C3), 26.7 (2×CH3), 17.5 (C4); MS [M+H]+: 525.

Conclusion

An efficient Microwave-assisted synthesis of 1, 2, 3-triazole derivatives has been carried out successfully under mild reaction conditions. All the final compounds were investigated for their in vitro antimicrobial activity. Compounds 8a, 8b, 8d, 8e, 13a, 13d and 13e showed promising antimicrobial activity compared with the standard. We observed that compounds not having substituents on phenyl ring showed very good antimicrobial activity compared to those having substituents.