Trans-bicyclo{2.2.0}hexane, if accessible, would, on thermal cleavage of the bridging bond, provide directly the chair-cyclohexane-1,4-diyl. This diyl has been discussed as a possible intermediate in the Cope rearrangement by Doering, McIver, and Dewar. It may also be involved in the thermal rearrangement of cis-bicyclo{2.2.0}hexane as the intermediate leading to 1,5-hexadiene, a product formed in competition with an inversion process. These two probably interrelated processes could then be studied from the point of view of a presumed common intermediate.

During the course of work directed at the synthesis of a trans-bicyclo{2.2.0}hexane derivative, variously functionalized trans-fused strained-ring bicyclic systems were examined including {4.3.0}, {4.2.0}, {3.2.0}, and {3.3.0} derivatives. The individual ring systems exhibited unexpected chemical behavior.

This work was contrasted with a previous effort by the exchange of the diazo and the carbonyl of a trans-{3.2.0}diazoketone so as to possibly avoid a strain driven bond shifting process during formation. It was found in this work that functionality required to prevent epimerization also inhibited the diazoexchange process. The reason was thought to be steric protection of the reactive site by methyl groups on the bridgeheads of the ring system. The system of the previous study was unencumbered sterically and reacted readily with diazoexchange reagents.

It was observed that as ring size diminished, efficiency of the photochemical Wolff rearrangement, the principle means of ring contraction, also diminished. This was contrasted with the corresponding cis-fused series at the {4.2.0} level. The cis-series was synthesized and ring contracted without side product formation and with much higher yields. The problem associated with the trans-fused series was thought to stem from the twisted nature of the ring system.

Ozonolysis of the ketene intermediates formed by the Wolff rearrangement in aprotic media to the corresponding ketones as a means of reducing the number of steps involved in multiple ring contractions of one ring, was shown to lead to unfavorable mixtures consisting mainly of partial cleavage products. This was shown to be independent of the ring system and was principly a function of steric factors about the ketene. The partial cleavage products observed were of the same types observed for the same reaction done on other ketenes as reported in the literature. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI