ACID CLEAVAGE OF HUMULENE 9,10-EPOXIDE. ANOMALOUS PRODUCTS AND EFFECTS OF STRAIN ON THE REACTION COURSE

Abstract
Summary On treatment of humulene 9,10-epoxide with BF3·OEt2 in AcOH, seemingly anomalous products 6-acetoxy-7-hydroxy-2,9-humuladiene and 6-acetoxy-2,7(13),9-humulatriene were obtained together with known compounds 2,9-diacetoxy-1,5,8,8-tetramethylbicyclo[8,1,0]undec-5-ene, 9-acetoxy-1,5,8,8-tetramethyltricyclo[8,1,0,02,6] undec-4ene and -5ene. The reaction course was well explained by the strain energy of four possible intermediates expected at the first stage of the transannular reaction.