Methylenation

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In organic chemistry, methylenation is a chemical reaction that inserts a methylene (−CH2) group into a chemical compound:

Typically, the reaction is used to prepare terminal alkenes from aldehydes and, less frequently, ketones.

Methods

Methylene-for-oxo reactions

A common method for methylenation involves the

phenyl, C6H5):[1]

A related reaction can be accomplished with Tebbe's reagent, which is sufficiently versatile to allow methylenation of esters:[2]

Other less well-defined titanium reagents, e.g., Lombardo's reagent, effect similar transformations.[3][4]

Carbanions derived from methylsulfones have also been employed, equivalently to the Wittig reaction.[5]

Other approaches

Ethenolysis is a method for methylenation of internal alkene as illustrated by the following example:

In principle, the addition of CH2 across a C=C double bond could be classified as a methylenation, but such transformations are commonly described as cyclopropanations.

References