Cyclopropanation 2-Nitropropane

Cationic cyclization. A key step in the synthesis of the diterpenes cafestol5 and atractyligenin4 involves a novel cation cyclization of bicyclic cyclopropanes to the tetracyclic systems of the diterpenes (equations I and II). Thus treatment of 1 with a slight excess of triflic anhydride and 2,6-lutidine effects cyclization to the rather unstable pentacycle 2 with the kaurene system. The related conversion of 3 to 4 can be effected with triflic anhydride and 2,6-di-r-butyl-4-methylpyridine in 1-nitropropane. 

Diazo-l,l,l-trifluoro-3-nitropropane reacts with enamines. This reaction goes through the intermediacy of a cyclopropane derivative which hydrolyzes to the corresponding ketone 47. ... 

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