The chemistry of terpenes. Part XIII. Synthesis of (+)-3β,7,7-trimethyl-anti,cis,anti-tricyclo[4,1,0,02,4]heptane and (±)-trans-3-(1-hydroxyethyl)-6,6-dimethylbicyclo[3,1,0]hexane, deamination products of the cis-caran-4-amines

Abstract

Syntheses of the novel, highly strained, tricyclic hydrocarbon, (+)-3β,7,7-trimethyl-anti,cis,anti-tricyclo[4,1,0,0^2,4]heptane (1) and of (±)-trans-3(1-hydroxyethyl)-6,6-dimethylbicyclo[3,1,0]hexane (2) are described. Cyclisation of the keto-aldehyde (10), obtained by the ozonolysis of (+)-car-3-ene (9) gives (+)-2-acetyl-6,6-dimethylbicyclo[3,1,0]hex-2-ene (11), which with diazoethane affords the pyrazoline, (–)-1β-acetyl-3,3,7β-trimethyl-cis,anti,cis-8,9-diazatricyclo[4,3,0,0^2,4]non-8-ene (12). Photolysis of this pyrazoline yields a mixture of (+)-2β-acetyl-3β,7,7-trimethyl-anti,cis,anti-tricyclo[4,1,0,0^2,4]heptane (13), its (+)-3α-epimer (14), and (+)-2-acetyl-3-ethyl-6,6-dimethylbicyclo[3,1,0]hex-2-ene (15). Removal of the acetyl group from compound (13) presented difficulty. Photolysis of the pyrazoline, methyl (+)-3,3,7β-trimethyl-cis,anti,cis-8,9-diazatricyclo[4,3,0,0^2,4]non-8-ene-1β-carboxylate (19), gives methyl (+)-3β,7,7-trimethyl-anti,cis,anti-tricyclo[4,1,0,0^2,4]heptane-2-carboxylate (20), its 3α-epimer (21), and methyl (+)-3-ethyl-6,6-dimethylbicyclo[3,1,0]hex-2-ene-2-carboxylate (22). Conversion of the ester (20) to the corresponding aldehyde (26) and photolysis of the latter yields the hydrocarbon (1).

Cyclisation of the keto-aldehyde (47) obtained from (+)-car-2-ene (46) affords (+)-3-acetyl-6,6-dimethyl-bicyclo[3,1,0]hex-2-ene (48), which on hydrogenation yields a mixture of trans- and cis-3-acetyl-6,6-dimethylbicyclo[3,1,0]hexane, (7) and (8), respectively. Reduction of the former yields the title alcohol (2).