carbonallylation

Carbonallylation is a term encountered in some chemical literature to describe reactions that install an allyl fragment together with another carbon-containing unit onto a substrate in a single operation. It is not a single, universally defined class, and different sources use the term differently. In broad terms, carbonallylation can refer to three-component coupling processes in which an allyl group and a carbon-containing unit are introduced across a substrate, or to carbonylation-allylation sequences in which a carbonyl group is formed or inserted concomitantly with an allylation step. As a result, the exact meaning depends on context and the authors’ preferred terminology.

Mechanistic frameworks for carbonallylation-like processes typically involve transition-metal catalysis, including palladium, nickel, or copper catalysts, and may proceed via three-component coupling, radical pathways, or carbonylation steps that insert CO into a metal–carbon bond prior to allyl transfer. Reagents commonly used include allyl electrophiles or nucleophiles, various carbon donors (such as aldehydes, boron reagents, or organometallic fragments), and carbon monoxide or CO surrogates. The aim is to construct C–C bonds that bear both an allyl moiety and a carbon-based fragment in a coordinated fashion.

Scope and challenges vary across reported examples. Key issues include control of regio- and stereoselectivity, compatibility with diverse functional groups, and suppression of competing pathways such as simple allylation, carboalkylation, or isomerization. The term’s lack of a single, accepted definition means practical use depends on the specific reaction system described in a given publication.

See also: carbonylation, allylation, carboalumination, carbonyl-allylation, three-component coupling.