Elimination-Addition Route The Carbenic Mechanism

This is a relatively rare route in which both elements of HX are eliminated from the /J-carbon, leaving a carbene (181) (equation 17). Among other reactions, the carbene may also capture the nucleophile, giving a /8-substitution product. 

The formation of t-butoxyvinyl ether (188) from bromomethylene-cycloheptene (187) and t-BuO- proceeds via intermediate alkylidene-carbene (Erickson and Wolinsky, 1965). 

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