Chemoselectivity in the Transannulaction of 1,2,3-Thiadiazoles and Alk-2-enenitriles: Specific Synthesis of 3-(Alk-1-enyl)isothiazoles

摘要

1,2,3-Thiadiazoles are precursors of thioacylcarbenes and thioketenes and show various reactions with unsaturated compounds. The rhodium-catalyzed reactions of 1,2,3-thiadiazoles and alk-2-enenitriles, including alkyl, aryl, and heteroaryl acrylonitriles, have been investigated, showing chemospecific reactivity to generate 3-vinylisothiazole derivatives via the (3+2) transannulation between the cyano group of alk-2-enenitriles and generated thioacylcarbenes. (Z)-Cinnamonitriles are less active than (E)-cinnamonitriles due to the strong coordination of the (Z)-C=C bond and the Rh catalyst. The current reaction provides a method for the synthesis of 3-vinylisothiazole derivatives.