Hydroboration with Pyridine Borane

Key words

hydroboration - pyridine boranes - haloboranes

Significance

A stable available pyridine-borane complex after the reaction with iodine gives a selective hydroborating agent, active at room temperature. Acetylenes can be transformed into ketones after oxidation. Mono-, di- and trisubstitut­-ed alkenes can be readily hydroborated leading to mono-adducts at room temperature. Functional groups like esters, amines and amides are tolerated.

Comment

Despite the numerous existing hydroborating agents, developed to date, there is still the lack of a cheap, selective, robust and stable reagent. Pyridine-borane complex is a stable and not air-sensitive liquid. On the reaction with iodine, it is transformed into a strong but selective hydroborating agent, that reacts equally well with alkynes and alkenes, tolerating reducible functional groups. The procedure is very simple and practical.