A Metal‐Free Eliminative Azide‐Olefinic Cycloaddition Route to Sulfonylated 1,2,3‐Triazoles From Vinyl Bissulfones: Impact of an Additional Sulfonyl Group on Regioselectivity

ABSTRACT This study explores the effect of an additional electron‐withdrawing sulfonyl group on the regioselectivity of triazole formation using vinyl bissulfones, a new class of acetylene equivalent and leads to the synthesis of a wide range of sulfonylated triazoles. The selectivity was influenced by the positioning of the second electron withdrawing vinyl sulfone group, which enhances the electron deficient nature of the double bond and also acts as a leaving group. Internal vinyl bissulfones generated a complex mixture of products. However, terminal vinyl bissulfones, regioselectively produced two types of 1,4‐disubstituted 1,2,3‐triazoles functionalized either with a CH 2 SO 2 Ar moiety or the ArSO 2 group directly attached to the triazole ring depending on the nature of the starting material. These metal‐free reactions, executed in water, are a new addition to the eliminative azide‐olefinic cycloaddition category of reactions. The results suggest that modified vinyl bissulfones are inexpensive and readily available starting materials for the synthesis of two distinct varieties of 1,4‐disubstituted sulfonylated 1,2,3‐triazoles in a regioselective fashion via unconventional routes.