RUTHENIUM-CATALYZED ALDOL AND MICHAEL REACTIONS OF NITRILES - CARBON-CARBON BOND FORMATION BY ALPHA-C-H ACTIVATION OF NITRILES

The ruthenium(II)-catalyzed reaction of nitriles with carbonyl compoun ds proceeds highly efficiently under neutral and mild conditions to gi ve alpha,beta-unsaturated nitriles. Under similar reaction conditions, nitriles react with olefins bearing electron-withdrawing groups to gi ve the corresponding Michael adducts. The efficiency of the reaction i s illustrated by the selective additions to alpha,beta-unsaturated ald ehydes and acetylenes bearing electron-withdrawing groups, which are d ifficult to perform using conventional bases. Chemoselective aldol and Michael reactions of nitriles can be performed in the presence of oth er active methylene compounds. Tandem Michael and Michael-aldol conden sations of nitriles 30 can be performed with high diastereoselectivity . These reactions can be rationalized by assuming oxidative addition o f ruthenium(0) to the alpha=C-H bond of nitriles and subsequent insert ions to carbonyl compounds or olefins. As the key intermediates and ac tive catalysts hydrido(N-bonded enolato)ruthenium(II) complexes, mer-R uH(NCCHCO(2)R)(NCCH(2)CO(2)R)(PPh(3))(3) (R = Me (41a), Et (41b), n-Bu (41c) have been upon treatment of RuH2(PPh(3))(4) (3) or RuH(C2H4)(PP h(3))(2)(PPh(2)C(6)H(4)) (4) with alkyl cyanoacetates. Kinetic study o f the catalytic aldol reaction of ethyl cyanoacetate with benzaldehyde indicates that the rate-determining step reaction of enolato complex 41 with aldehydes.