Reaction of Diisobutylaluminum Borohydride, a Binary Hydride, with Selected Organic Compounds Containing Representative Functional Groups.

The binary hydride, diisobutylaluminum borohydride [(Bu)AlBH], synthesized from diisobutylaluminum hydride (DIBAL) and borane dimethyl sulfide (BMS) has shown great potential in reducing a variety of organic functional groups. This unique binary hydride, (Bu)AlBH, is readily synthesized, versatile, and simple to use. Aldehydes, ketones, esters, and epoxides are reduced very fast to the corresponding alcohols in essentially quantitative yields.

Hydride as a leaving group in the reaction of pinacolborane with halides under ambient Grignard and Barbier conditions. One-pot synthesis of alkyl, aryl, heteroaryl, vinyl, and allyl pinacolboronic esters.

Grignard reagents (aliphatic, aromatic, heteroaromatic, vinyl, or allylic) react with 1 equiv of 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (pinacolborane, PinBH) at ambient temperature in tetrahydrofuran (THF) to afford the corresponding pinacolboronates. The initially formed dialkoxy alkylborohydride intermediate quickly eliminates hydridomagnesium bromide (HMgBr) and affords the product boronic ester in very good yield. Hydridomagnesium bromide (HMgBr) in turn disproportionates to a 1:1 mixture of magnesium hydride (MgH(2)) and magnesium bromide (MgBr(2)) on addition of pentane to the reaction mixture.