A Stereospecific Access to Allylic Systems Using Rhodium(II)−Vinyl Carbenoid Insertion into Si−H, O−H, and N−H Bonds

Abstract

Rhodium-catalyzed decomposition of α-vinyldiazoesters in the presence of silanes, alcohols, ethers, amines, and thiols have been shown to produce the corresponding α-silyl, α-hydroxy, α-alkoxy, α-amino, and α-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 ester function or achiral α-vinyldiazoesters and Doyle's chiral catalyst Rh2(MEPY)4. In the former approach, pantolactone as chiral auxiliary gave diastereoselectivities of up to 70%, while the second approach produced the desired allylsilane with ee as high as 72%. On the other hand, Rh2(MEPY)4-catalyzed insertion into the O−H bond of water led to poor or no enantioselectivity in good agreement with recent literature reports.