Microwave-Assisted Azide-Alkyne Cycloaddition in Water Using a Heterogeneous Cu-Catalyst

Abstract

Several triazoles have been synthesized. They were obtained by a Cu-catalyzed cycloaddition of azides and alkynes. The reaction takes place in aqueous media under microwave irradiation using a copper catalyst based on porous glass. The products have been characterized by infrared, gas chromatography–mass spectrometry, ¹H NMR, and ¹³C NMR in addition to melting = point determination. Furthermore the in situ building of some azides and alkynes and the influence of the used metal species was investigated.

GRAPHICAL ABSTRACT

Keywords:

• Alkyne
• azide
• copper
• heterogeneous catalysis
• microwave

Notes

Note. Reaction conditions: 0.5 mmol azide (1), 0.55 mmol alkyne (2a), 50 mg catalyst, theoretical Cu-loading 1 wt%, 50 mg sodium ascorbate, 5 ml deionized H₂O, microwave heating, 10 min, 80 °C (300 W).

^a Isolated yields (averages from two independent reaction sequences).

^b The analytical yield was determined from conversion calculated via calibration with benzyl azide measured with GC-FID.

^c Same product as entry 9.

^d Alkyne = 2-(trimethylsilyl)phenyl trifluoromethanesulfonate.

^e Reaction at 100 °C.

Note. Reaction conditions: 0.5mmol chloride, 0.5mmol NaN₃, 0.55mmol 2a, 50mg catalyst, theoretical Cu-loading 1 wt%, 50mg sodium ascorbate, 5ml deionized H₂O.

^a Microwave heating, 10min (300 W).

^b The conversion of chloride was calculated from calibrated peak area of GC-FID.

^c Yield of the azide was calculated from the peak area ratio of the product.

^d Without sodium ascorbate.

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