We report here the evidence for hydride abstraction-recombination mechanism in the carbenic CH insertion reaction of alkoxides obtained by the stereochemical investigation'of alkylidenemethylene carbenoid (R'R2C= C: a--MX): insertion into aCH bond of secondary alkoxides. In an examination of the oxy anionic effect on the selective CH in~ ertion,~ alkylidenemethylene carbenoid was inserted into the aCH bond of alkoxides ...