A STEREOSPECIFIC ACCESS TO ALLYLIC SYSTEMS USING RHODIUM(II)-VINYL CARBENOID INSERTION INTO SI-H, O-H, AND N-H BONDS

Rhodium-catalyzed decomposition of alpha-vinyldiazoesters in the prese nce of silanes, alcohols, ethers, amines, and thiols have been shown t o produce the corresponding alpha-silyl, alpha-hydroxy, alpha-alkoxy, alpha-amino, and alpha-thioalkoxy esters in generally good yield with a complete retention of the stereochemistry of the double bond of the diazo precursor. An extension of the process in homochiral series has also been devised using either a chiral auxiliary attached to the este r function or achiral alpha-vinyldiazoesters and Doyle's chiral cataly st Rh-2(MEPY)(4). In the former approach, pantolactone as chiral auxil iary gave diastereoselectivities of up to 70%, while the second approa ch produced the desired allylsilane with ee as high as 72%. On the oth er hand, Rh-2(MEPY)(4)-catalyzed insertion into the O-H bond of water led to poor or no enantioselectivity in good agreement with recent lit erature reports.