REGIOCHEMISTRY AND STEREOCHEMISTRY .90. FROM CHLOROCYCLOBUTANONES TO CAGE COMPOUNDS - STRAIN, PROXIMITY EFFECTS, AND TANDEM REARRANGEMENTS

A review of studies in our laboratory on the chemistry of alpha-chloro cyclobutanones fused to 5-, 6-, and 8-membered rings is presented. The major feature of such compounds is the high propensity to undergo cin e substitution with nucleophiles, which is initiated by the intermedia cy of oxidoallyl cations. The cine substitution products often undergo interesting transformations which become evident especially when the 4-membered ring is fused to a tetrahydrofuran or a tetrahydropyran. In such cases, beta elimination of the alcohol chain with ring opening o f the heterocyclic ring leads to formation of cyclobutenones, which un dergo further transformations. Proximity effects as well as strain are responsible for unusual tandem rearrangements and formation of cage c ompounds.