A mechanistic alternative for the intramolecular hydroboration of homoallylic amine and phosphine borane complexes.

Intramolecular hydroboration is demonstrated starting from homoallylic amine boranes upon activation by iodine. The process involves a B-iodoborane complex as the intermediate and may occur via internal displacement of iodide by the alkene to generate a cationic borane-alkene pi-complex on the way to hydroboration products. The reaction can be carried out using a catalytic amount of iodine.