Regio- and diastereoselective organo-zinc promoted arylation of trans 2,3-diaryloxiranes by arylboronic acids: stereoselective access to trans 2,3-diphenyl-2,3-dihydrobenzofuran

Ortho-oxo substituted trans 2,3-diaryloxiranes were regio and stereoselective arylated by aryl zinc reagents, obtained from the corresponding boronic acids by B-Zn exchange. The reaction was quite general, irrespective to the aryl nucleophile and roceeded via a ring opening at the -carbon with respect to the substituted aryl ring. The stereoselectivity was from high to complete toward the alcohol resulted from retention of configuration at the electrophilic carbon. The method allowed a direct and high yielding access to trans 2,3-diphenyl-2,3-dihydrobenzofuran, which is a key structural motif in resveratrol dimers as viniferins. The use of enantioenriched starting diaryloxiranes resulted in no loss of stereochemical integrity in the final trans 2,3-dihydrobenzofuran, which was characterized for the first time in enantioenriched form.