Catalyst-free and solvent-free hydroboration of aldehydes

A simple catalyst-free and solvent-free method for the hydroboration of various aldehydes bearing a wide array of electron-withdrawing and electron-donating groups was developed. Unlike aldehydes, the addition of boranes to ketones is less efficient and is thus advantageous for the chemoselective reduction of the former ones. It is suggested that the described transformation proceeds with the formation of Lewis acid-base adducts, which facilitates further hydroboration.