Synthesis of organoboron compounds via the transition metal-catalyzed addition and coupling reaction of (alkoxo)diborons

Transition metal-catalyzed additions and cross-coupling reactions of the me tal-metal compounds have attracted considerable attention as direct routes to prepare various organometallic compounds. Although the corresponding rea ctions of boron compounds had not yet been well developed, we recently repo rted the first platinum (0)-catalyzed addition reaction of bis(pinacolato) diboron (Id) to either terminal or internal alkynes to give cis-bis(boryl)a lkenes. The addition of id to 1,3-dienes and alkenes with platinum(0) compl exes afforded a new access to the cis-1,4-bis(boryl)butene and bis(boryl)al kane derivatives. The palladium (0)-catalyzed cross-coupling reactions of 1 d with aryl halides or triflates, and allyl chlorides or acetates gave the corresponding aryl- and allylboronates in high yields, which provides the f irst one-step procedure for organoboronic eaters from organic electrophiles . Since (alkoxo)diborons are thermally stable and easily handled in air, th e reagent can be useful as boron nucleophiles for cross-coupling reactions with organic halides. The mechanisms and the synthetic applications of thos e reactions are discussed.