Diethyl ether-boron trifluoride (1/1) induced transannular cyclization reaction of humulene 2,3-epoxide

Article abstract of DOI:10.1246/bcsj.69.459

The treatment of (6E, 9E)-2,3-epoxy-3,7,11,11-tetramethylcycloundeca-6,9-diene with Et₂O·BF₃ produced four novel transannular cyclized compounds of (4E)-(1S*, 8S*, 9S*)-8-acetoxy-6,6,9-trimethyl-2-methylenebicyclo[7.2.0]undec-4-ene (13), (2Z, 4E)-(1S*, 8S*, 9S*)-8-acetoxy-2,6,6,9-tetramethylbicyclo[7.2.0]undeca-2,4-diene (14), (6E)-(1R*, 2R*, 3S*, 10R*)-3-acetoxy-2,5,5-trimethyl-9-methylenebicyclo[8.1.0]undec-6-ene (15), and (4E)-(1S*, 2S*, 8S*, 9S*)-2,8-diacetoxy-2,6,6,9-tetramethylbicyclo[7.2.0]undec-4-ene (16) together with three new acetates: (2E, 5E, 8E)-1-acetoxy-2, 6,10,10-tetramethylcycloundeca-2,5,8-triene, (1E, 6E)-3,9-diacetoxy-2,5,5,9-tetramethylcycloundeca-1,6-diene, and (4E, 7E)-1-acetoxy-3,3,7-trimethyl-11-methylenecycloundeca-4,7-diene. The configurations of the bicyclo[7.2.0]undecane skeletons (13, 14, and 16) and 15 maintained the shape of TC and CT conformers of the original epoxide, respectively.