Takanao Taketomi

Chemoselective asymmetric hydrogenation of α,β-unsaturated carbonyl compounds to allylic alcohols catalysed by [Ir(binap)(cod)]BF4-aminophosphine

Asymmetric hydrogenation of (E)-4-phenyl-3-buten-2-one by use of [Ir(binap)(cod)]BF4 and o-di-methylaminophenyldiphenylphosphine afforded (E)-4-phenyl-3-buten-2-ol in 97% chemoselectivity and in 65% enantiomeric excess. A mixed ligand iridium dihydride complex containing both BINAP and the aminophosphine ligand has been shown to be the catalytically active species.

Cationic rhodium(I) complex-catalysed asymmetric isomerisation of allylamines to optically active enamines

The cationic rhodium(I) complex(+)- or (–)-2,2′bis(diphenylphosphino)-1,1′-binaphthyl(cyclo-octa-1,5-diene)rhodium perchlorate, effectively catalyses the isomersiation of N,N-diethylnerylamine or N,N-diethylgeranylamine to produce optically active N,N-diethylcitronellal-(E)-enamine with excellent enantioselectivity (> ca. 95% enantiomeric excess) and chemoselectivity (> ca. 98%).

Further studies on the reactivity of π-cyclo-octenyl-π-cyclo-octa-1,5-dienecobalt. Formation of π-cycloheptadienyl-π-cyclo-octa-1,5-dienecobalt

Treatment of π-cyclo-octenyl-π-cyclo-octa-1,5-dienecobalt, Co(C8H13)(C8H12), with cyclo-heptatriene (C7H8) afforded the title compound, Co(C7H9)(C8H12), from which was derived Co(C7H9)(CO)2. Co(C8H13)(P(n-C4H9)3]2 and Co(C8H13)(PPh3)2 were obtained from Co(C8H13)(C8H12) and the corresponding phosphine. The formation of the title compound in n-heptane at 65°C follows a composite rate equation, R=k[Co][C7H8]+k′[Co]½. The kinetics, volatile products analysis, and isolation of a diamagnetic, dinuclear complex [Co(C7H8)(C8H12)]2 are used to infer the reaction pathways.

π-Cycloheptadienyl-π-cyclo-octa-1,5-dienecobalt; fluxional bonding

The title complex exhibits a temperature-dependent 1H n.m.r. spectrum indicative of proton averaging between –25 and 75 °C. The stable molecular conformation was inferred from the limiting spectrum below –25 °C. The averaging of diene protons was interpreted in terms of a planar rotation of the ligand and the energy barrier calculated from the temperature dependence was about 14 kcal mol–1.

Bicyclo[3,3,0]octa-2,4-dien-1-yl(cyclo-octa-1,5-diene)cobalt

Cyclo-octenylcyclo-octa-1,5-dienecobalt Co(C8H13)(C8H12)(I) reacts with cyclo-octa-1,5-diene to give the title complex (II). An intermediate 1–3-η-cyclo-octa-1,5-dienyl(cyclo-octa-1,5-diene)cobalt complex Co-(C8H11)(C8H12)(III) has been isolated and characterised. A possible reaction path of the dehydrogenative ring closure of (I) to (II) is discussed.