A Little of Everything Various Carbanions and Enolates Yielding Ring Expansion

A Little of Everything Various Carbanions and Enolates Yielding Ring Expansion 

In contrast to what we have practiced in this writing, reasonable solutions to complex mechanistic situations can sometimes be found after just a few explanatory words. In this reaction, not an easy one to foresee to be sure, a probable mechanism unfolds after the recognition of very few facts. 

All that is taking place is ring expansion, lactone ring opening with decarboxylation, and finally a local oxidation of the carbon atom at which the sulfone substituent in II is placed. 

For the ring expansion step an extra carbon is needed, of course, and the 7 carbon of the lactone ring appears to be the best candidate. It not only bears a relatively labile C-0 bond that upon disconnection might evolve into the carboxylate unit required for decarboxylation, but this carbon is also proximal to the a anion of the cyclohexanone portion of molecule I that is expected to appear in strong basic medium. The union of these two carbons will produce a cyclopropyl ketone whose central C-C bond might break up, prodded by the carbonyl unit, to yield a seven-membered ring system. 

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