Temhedmn Letters, Vo1.32. No.34, pp 4227A230.1991 Printedin Greak Britain 0040-4039/91 $3.00 + .OO Pergamcm Press plc ENANTIOSELECTIVE REDUCTION OF P-KETO ESTERS Douglass F. Taber* and Lee J. Silverberg Department of Chemistry & Biochemistry, University of Delaware, Newark, DE 19716 USA zyxwvutsrqponmlkjihg Summary: Highly enantioselective reduction of P_keto esters with BINAPeRu catalyst can be effected at 50 psig H2 and 800, using a Parr shaker. A simplified preparation of the BINAP.Ru catalyst is reported. In 1987 the Nagoya and Takasago groups, working in collaboration, reported 1*2that a catalyst prepared by treating BINAP ruthenium diacetate 1 with methanolic HCl would effect the hydrogenation of a P_keto ester 2 to the corresponding alcohol 3 with excellent turnover and stunning enantioselectivity (99:l). zyxwvutsrqponmlkjihgfedcbaZ 1 .w-p,,DCH, (s)-BE;2 /-,qyOCH, c99:1j 0 0 HO 0 2 1500 psig H2 58 hours 3 In the more than three years since the initial publication, only two3 other research groups have reported the use of this procedure in a target-directed synthesis. The reasons for this are easy to understand. Ruthenium complex 1 must be prepared (three steps) and stored under controlled atmosphere conditions (Schlenkware or glove box). Further, the hydrogenation is carried out at 1500 psig, a pressure not routinely available to the organic synthesis chemist. We have found that the direct product from combination of commerc ially available BINAP and (RuC12cyclooctadiene), in the presence of triethylamine 113 is a very active catalyst that shows good selectivity in the hydrogenation. This observation makes it possible to carry out these hydrogenations without purifying BINAP*RuC12]2Et3N and BINAP.Ru(OAc)2, two very air sensitive substances.4 4227