Synthesis and Stereochemical Structures of Novel Spiro[Benzocycloheptene-6(5 H ),3′-[3 H ]Pyrazol]-5-Ones

Abstract

Reaction of a variety of 6-arylmethylene-6,7,8,9-tetrahydro-5H-benzocycloheptene-5-ones 1a–f with nitrilimines (generated in situ by triethylamine dehydrohalogenation of the corresponding hydrazonoyl chlorides 2) in refluxing benzene, afforded the corresponding spiro[benzocycloheptene-6(5H),3′-[3H]pyrazol]-5-ones 3a–h and not the isomeric forms spiro[benzocycloheptene-6(5H),4′-[4H]pyrazol]-5-ones 4 in a highly regioselective manner. The stereochemical configuration of the isolated products was established to be 3′R, 4′S based on single crystal X-ray diffraction of 3a.