Synthesis of 1,4‐Disubstituted 1,2,3‐Triazoles from Terminal Vinyl Sulfones in Ionic Liquid: A Metal‐Free Eliminative Azide‐Olefinic Cycloaddition Route to Triazolyl Carbohydrates and Triazole‐linked Bissaccharides

Abstract

Several terminal vinyl sulfones, derived from styrene epoxide and monomesylated glycerol were reacted with benzylazide in a metal‐free condition to afford regioselectively 1,4‐disubstituted 1,2,3‐triazoles (1,4‐DTs) via Eliminative Azide‐Olefinic Cycloaddition (EAOC) reactions. The stereoelectronic repulsions between the aryl/alkyl groups attached to the azido and vinyl sulfone functionalities play a significant role in deciding the outcome of the reactions. The N, N‐dimethyl ethanolammonium formate‐water mixture consisting of a biodegradable ionic liquid turned out to be the best solvent system to reduce significantly the reaction time and increase the yield of products in almost all cases. Furthermore, a pair of exocyclic terminal vinyl sulfone‐modified carbohydrates were prepared from protected‐glucofuranoside and ‐allofuranoside. These carbohydrates were reacted under the EAOC conditions with a host of organic azides to afford the corresponding 1,4‐disubstituted 1,2,3‐triazole modified carbohydrates. Azido sugars were also reacted with terminal vinyl sulfone modified carbohydrates under similar conditions to afford 1,4‐disubstituted 1,2,3‐triazole linked bissacharides. This powerful strategy serves as a potential yet practical route for delivering two carbon unit (required for the C4‐C5 of the 1,2,3‐triazole ring) directly connected to sugar body in place of a sugar alkyne.

Ionic liquids for the green synthesis of 1,2,3-triazoles: a systematic review

“…Sarkar et al reported a new metal-free approach for the synthesis of 1,2,3-triazoles ( 51–51f ), in which various vinyl sulfones were treated with diversified organic azides via an eliminative azide-olefinic cycloaddition (EAOC) reaction (Scheme 55). 132 It was observed that the reaction medium played a significant role in synthesizing 1,2,3-triazoles as the reaction timing and product yield depended on it. The highest yield of triazoles (68%–75%) was obtained when phenyl-based vinyl sulfones were treated with benzyl azides in a DAF : H 2 O (1 : 1 v/v) solvent system at 100 °C.…”