Studies in cuprate rearrangement and stannylcupration: Application to the stereo- and enantiospecific synthesis of a stannyldiene C-10-C-15 fragment of des-epoxy-rosaramycin

Metallate rearrangements were performed on alpha-(carbamoyloxy)alkenyl stannanes 4 in high yields to prepare (+/-)-8a and (+/-)-8b via alkyl transfer but failed when stannyl and stannylvinyl transfers were attempted to give 10ab and lab after quenching with Mel. After we optimized conditions on dihydrofuran 13, a model study, the dihydrofuran 19 could deliver cuprate rearrangements, leading after methylation to the stannyl derivative 10 and the stannyldiene 1 in good yields. A second approach for the synthesis of stannyldienes was envisaged via a Stille Pd(0) coupling reaction using (E)-1,2-bis(tributylstannyl)ethylene 11. An efficient method was performed by stannylcupration of the enyne (+/-)-24 which gave the expected stannyldiene (+/-)-1 in good yield and with high regio-and stereocontrols. Copyright (C) 1996 Elsevier Science Ltd