Dithiane-initiated cascade to eight-membered sulfur-containing pyrazoles <i>via</i> decarboxylative aromatization

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, <i>Z</i>-pyrazoline intermediates can be selectively isolated under mild conditions (<i>Z</i>/<i>E</i> > 20 : 1).