Dithiane-initiated cascade to eight-membered sulfur-containing pyrazoles via decarboxylative aromatization†
Abstract
A base-mediated cascade reaction between alkynyl-1,3-dithianes and α-diazoesters enables the efficient and thermally tunable synthesis of eight-membered sulfur-containing pyrazoles. This transformation proceeds through a regio- and stereoselective [3+2] cycloaddition, followed by 1,3-dithiane ring expansion and decarboxylative aromatization. Notably, Z-pyrazoline intermediates can be selectively isolated under mild conditions (Z/E > 20 : 1).