organoallyl

Organoallyl is a term used in chemistry to describe compounds that feature an allyl fragment, CH2=CH-CH2-. The expression covers two closely related senses. First, organic molecules in which an allyl group is bonded to a nonmetal atom or framework, such as allyl alcohol, allyl ethers, and allyl silanes. Second, organometallic species in which the allyl fragment acts as a ligand bound to a transition metal in an η3-fashion. In the latter case, the three-carbon allyl unit is delocalized across the fragment and the metal, enabling interesting reactivity in catalytic cycles.

In η3-allyl complexes, the allyl ligand binds through all three carbons to the metal, a binding mode that allows facile migration and diversification of reactivity. This makes allyl groups versatile handles for carbon–carbon bond formation and for carrying the allyl unit into downstream transformations. Organically, allyl groups can participate in nucleophilic additions, substitutions, and cross-coupling processes when coordinated to or transferred by metals.

Preparation and occurrence: Organic allyl derivatives are prepared by standard allylation methods, including allylation of carbonyl compounds or substitution reactions that install the allyl moiety. In organometallic chemistry, π-allyl ligands are commonly generated by oxidative addition of allyl halides to low-valent metals or by transmetalation from allyl reagents such as allyl boranes, silanes, or stannanes.

Applications: The Tsuji–Trost allylation is a prominent example in which a π-allyl–metal complex transfers the allyl unit to nucleophiles, forming homoallylic products. η3-allyl complexes of nickel, palladium, ruthenium, and other metals are widely used as catalysts and intermediates in organic synthesis, cross-coupling, and polymerization, with simple examples including allyl chloride, allyl alcohols, and various organoallyl reagents.