Stereospecific formation of 2-[(E)-alk-1′-enyl]benzoic acids in an unusual reaction of thiophthalides with aldehydes
Abstract
The reaction of thiophthalides 1 with aldehydes 3 in the presence of lithium tert-butoxide at –60 to 25 °C results in the stereospecific formation of only trans 2-(alk-1′-enyl)benzoic acids 4 in fairly good yields in one-pot operations. This reaction is proposed to proceed via episulfide formation followed by sulfur extrusion, and corroborated by an unprecedented reaction of phthalide with thiobenzophenone giving the acid 11a under similar conditions.