Synthesis and Applications of 3‐Phenylthio‐2‐Sulfolenes

Abstract

Treatment of 3-phenylthio-2-sulfolene (1) with an equimolar proportion of butyllithium at -78 ·C in THF followed by addition of an electrophiIe gave the 2-substituted 3-phenylthio-2-sulfolenes (2). The deprotonation was found to proceed only at the vinylic C-2 position. Some of the 2-sulfolenes 2 underwent desulfonylation upon heating with base. Of particular interest was the conversion of 3-phenylthio-2trimethylsilyl-2-sulfolene (2h) to its 3-sulfolene isomer 6 by sequential addition of butyllithium and salicylie acid at low temperatures. The 3-sulfolene 6 was desuIfonylated by Kugelrohr distillation at ISO •C under vacuum to give (Z)-2-phenylthio-l-trimethylsilyl-l,3-butadiene (8). The regiochemistry of the Diels Alder reaction of this highly reactive diene 8 was found to be controlled by the phenylthio group, and the stereochemistry is endo addition. Diene 8 was oxidized to its sulfone derivative 12 which also underwent a stereospecific Diels-Alder reaction. S3