Chirality transfer from a biphenyl axis to a spiro centre and its reverse: sequential self-immolation

Abstract

Schmidt reaction of ( S)-1-(2′, 4′, 6-trimethoxy-4, 6′-dimethylbiphenyl-2-yl)ethanone 8 furnished the expected amide 9 (43%) accompanied by ( S)-2, 7′-dimethoxy-3′, 5′, 6-trimethylspiro[cyclohexa-2, 5-diene-1, 1′-(1 H)isoindole]-4-one 12 (30%) which on reduction with zinc and acetic acid and subsequent methylation regenerated ketone 8. Schmidt rearrangement of the ketone 1 provided besides the expected amide 2 the dienone 3 in which chirality has been transferred from the biphenyl axis to the spiro centre. Reductive cleavage and subsequent methylation of 3 regenerated 1. [Display omitted]