Diastereoselective formation of tertiary stereocenters via Mizoroki-Heck reaction

The diastereoselective Mizoroki-Heck reaction of N-benzylpyrrolidines that incorporate a protected allylic alcohol moiety allows the synthesis of enantiomerically pure pyrrolo[1,2-b]isoquinolines, generating a tertiary stereocenter. The best results were obtained with the use of bulky phosphanes, as P(o-Tol)₃. When a good leaving group, such as pivaloyl is used as a protecting group, the trans-10-vinyl substituted pyrroloisoquinoline (10S,10aS)-2a is obtained as the major diastereoisomer in moderate yield. On the other hand, when the allylic alcohol is protected as a silyl ether, the protected alcohol is retained, obtaining an enol ether, whichafter deprotection and reduction leads to the trans-10-hydroxymethyl substituted pyrrolisoquinoline (10S,10aS)-5, in enantiomerically pure form, with complete diastereoselectivity.