Stereocontrol in the intramolecular Buchner reaction of diazoamides and diazoesters

Dirhodium(II) catalysed decomposition of diazoamide 5 resulted in formation of β-lactams 6/7 by intramolecular C–H insertion, the intramolecular Buchner reaction being disfavoured for conformational reasons. The diazoamide 8, however, gave products resulting from both the intramolecular Buchner reaction and C–H insertion. Chiral diazoesters 14–16 derived from α-substituted benzyl alcohols gave cycloheptatrienes in a highly diastereoselective manner; the norcaradiene isomer of the cycloheptatrienes was readily intercepted in a Diels–Alder reaction with 4-phenyl-1,2,4-triazoline-3,5-dione to give adducts 19–21.