TRANSMETALATION REACTIONS OF ORGANOSAMARIUM REAGENTS - CHLOROSILANE-ACCELERATED COPPER-CATALYZED CONJUGATE ADDITIONS

TMSCl accelerates the conjugate addition of in situ prepared organosamarium reagents to alpha,beta-unsaturated carbonyl compounds and nitriles in the presence of HMPA and catalytic amounts of Cu(I) salts. Reactions at -78-degrees-C leads to silyl enol ethers which are isolated or cleaved with TBAF to give beta-alkylated ketones in 30-90% overall yield. Catalysis is most efficient in the presence of 4 equiv of TMSCl and HMPA. HMPA is also necessary for the in situ preparation of the organosamarium species from alkyl halide and SmI2. Some functional groups (chloride,ether,alkene, amide) are tolerated in this process. In the absence of Cu(I) salts, 1,2-additions of organosamarium reagents to carbonyl groups are also dramatically accelerated by TMSCl/HMPA and occur within minutes at -78-degrees-C.