hydrostannylation

Hydrostannylation is a chemical transformation in which a tin hydride, most commonly tributyltin hydride (Bu3SnH), adds across a carbon–carbon multiple bond to form organotin compounds, typically vinyl or alkylstannanes. The reaction is widely used in organic synthesis to install a tin-containing handle that can be elaborated further by palladium-catalyzed cross-coupling or other tin-based transformations.

Mechanistically, hydrostannylation proceeds via a radical chain. A radical initiator such as AIBN or photochemical activation generates Bu3Sn•, which adds to the unsaturated substrate to form a carbon-centered radical. This radical then abstracts a hydrogen atom from another molecule of Bu3SnH to yield the organotin product and regenerate Bu3Sn•, propagating the chain. The process is typically carried out under inert conditions with organic solvents and often at elevated temperature.

In alkynes, hydrostannylation is generally regioselective, with the tin moiety installed at the less substituted carbon of the former triple bond, producing vinylstannanes suitable for Stille-type cross-couplings. For alkenes, hydrostannylation furnishes alkylstannanes. The stereochemical outcome depends on substrate and conditions, and mixtures can arise with more substituted substrates.

Applications include the preparation of vinylstannanes for subsequent cross-coupling to form carbon–carbon bonds, enabling convergent syntheses and short linear sequences in natural product and material syntheses. Limitations include the toxicity and environmental concerns of tin reagents, the need for radical conditions that can affect sensitive functionalities, and the requirement to efficiently remove tin residues from products.