trialkylborane

Trialkylboranes are organoboron compounds with the general formula R3B, where R represents an alkyl group. These compounds are characterized by a boron atom bonded to three carbon atoms. The boron atom in trialkylboranes is electron-deficient, possessing an empty p-orbital, which makes them Lewis acids. This property is central to their reactivity. They readily react with Lewis bases, such as amines or ethers, to form adducts.

Trialkylboranes are typically prepared by the reaction of a Grignard reagent or an organolithium reagent with a boron trihalide, such as boron trifluoride or boron trichloride. For example, the reaction of three equivalents of methylmagnesium bromide with boron trifluoride yields trimethylborane.

One of the most significant applications of trialkylboranes is in hydroboration, a reaction where a boron-hydrogen bond adds across a carbon-carbon double or triple bond. This process is stereoselective and regioselective, often leading to the syn addition of hydrogen and boron. The resulting organoborane intermediate can then be further functionalized through oxidation, amination, or other reactions, providing a versatile route to a variety of organic compounds, including alcohols and amines. Trialkylboranes are also used as reducing agents in organic synthesis, particularly in the reduction of functional groups. Their Lewis acidity also makes them useful catalysts in certain polymerization reactions.