Retro-Birch reduction

The Y appendage of 2-cyclohexenone 191 cannot be directly disconnected by an alkylation transform. (y-Extended enolates derived from 2-cyclohexenones undergo alkylation a- rather than y- to the carbonyl group). However, 191 can be converted to 192 by application of the retro-Michael transform. The synthesis of 192 from methoxybenzene by way of the Birch reduction product 193 is straightforward. Another synthesis of 191 (free acid) is outlined in... 

Birch reduction, and a Diels-Alder disconnection is required. There are two possible retro Diels-Alders on a cyclohexadiene the one that places the EWG on the dienophile is the better disconnection (leading to the more favorable Diels-Alder). 

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