In a typical reaction ethyl diazoacetate (a well-known carbene precursor) and dirhodium tetraacetate react with hexane; the insertion into a C−H bond occurs 1% on one of the methyl groups, 63% on the alpha-methylene unit and 33% on the beta-methylene unit.
[3] the metal that stabilizes the carbene, dissociates at the same time but not to the same degree as carbon–carbon bond formation and hydrogen atom migration.
It does, however, serve as a premier example of a metal-catalyzed C–H functionalization reaction, which some authors also refer to as C–H activation (sensu lato).
The metal employed as a catalyst in this reaction historically was copper until superseded by rhodium.
Most successful reactions are intramolecular within geometrically rigid systems, as pioneered by Wenkert (1982) [4] and Taber (1982).