Extension of a One-Pot Synthesis of Bicyclo[n.4.0]alkanols; Indications of Scope and Limitations for Formation of Substituted Bicyclo[n.4.0]alkanols

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Novel bicyclo[n.2.0]alkan-1-ols with incorporation of methyl substitution at the C6 bridgehead and C2 position on a six-member ring, and incorporation of methyl substitution at the C2 position on a five-member ring were obtained. The presence or absence of a group at these positions had a role in the preference of the major stereochemical isomer observed. Potential limitations of the cyclisation methodology was observed when the ketone was hindered (camphor), and where conjugation was present in the enolate. By contrast, another functional group, as illustrated with 1,4-cyclohexanedione mono-ethylene ketal 24, can be incorporated in the bicyclo[4.2.0]octan-1-ol, and the ketal group converted to a ketone, as in 28, without disrupting the bicyclo[4.2.0]octan-1-ol ring.