437 Journal of Organometallic Chemistry, 285 (1985) 431-447 Ekevier Sequoia S.A., Lausanne - Printed in The Netherlands zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONM MORE HIGHLY MIXED, HIGHER ORDER CYANOCUPRATES “R,(24bienyl)Cu(CN)Li,“. EFFICIENT REAGENTS WHICH PROMOTE SELECTlYE LIGAND TRANSFER BRUCE H. LIPSHUTZ l **, JOSEPH A. KOZLOWSKI, DAVID A. PARKER, SAM L. NGUYEN, and KEITH E. MCCARTHY Department of Chemistry, University of California, Santa Barbara, CA 93106 (U.S.A.) (Received July 17th, 1984) Summary The combination of an organolithium (RrLi) and 2Jithiothiophene (Zthienyl) with CuCN forms a new reagent, “R,(2&ienyl)Cu(CN)Li,.” This species selec- tively transfers the R-r ligand in substitution reactions with epoxides and halides. In conjugate addition processes, the cuprate reacts with unhindered substrates, while &/Misubstituted cases unexpectedly afford products resulting from 1,Zaddition of the thiophene group. The prospects for use of these reagents in the synthesis of polyene macrolide antibiotics are discussed. In applying higher order, mixed cuprate technology [l] (i.e., R,Cu(CN)Li,, 1, from 2 RLi + CuCN) to the formation of an all syn-1,3-polyol network 2 character- istic of the polyene macrolides [2] (e.g., Roflamycoin, 3), it was recognized that a 1. M$,Cu(CN)Li2 Ph-0 l 2. epoxidotion 3. repeat 1. and 2. 2 related strategy could be invoked for coupling of this unit with a functionalized polyene. Clearly, participation of a vinyl organometallic intermediate 4 in cuprate formation would be required. As 4 would necessitate its own preparation, there was tremendous incentive to devise a modified protocol wherein only one equivalent of 4 need be utilized in cyanocuprate generation, yet which would encourage selective * Alfred P. Sloan Foundation fellow. 1984-1986. 0022-328X/85/$03.30 0 1985 Elsevier Sequoia S.A.