- Iridium-catalyzed asymmetric hydrogenation of α-substituted α,β-unsaturated acyclic ketones: Enantioselective total synthesis of (-)-mesembrine
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A highly efficient asymmetric hydrogenation of α-substituted α,β-unsaturated acyclic ketones catalyzed by chiral spiro iridium complexes for the preparation of chiral 2-substituted allylic alcohols has been developed (ee up to 99.7%). This method provides a concise route to (-)-mesembrine (34% yield, 12 steps).
- Zhang, Qian-Qian,Xie, Jian-Hua,Yang, Xiao-Hui,Xie, Jian-Bo,Zhou, Qi-Lin
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supporting information
p. 6158 - 6161
(2013/02/23)
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- Isoxazole compounds as cyclooxygenase inhibitors
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A class of substituted isoxazolyl compounds is described for use in treating cyclooxygenase-2 related disorders. Compounds of particular interest are defined by Formula I STR1 wherein R1, R2, and R3, are described in the specification.
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- Rhodium carbonyl-catalyzed carbonylation of unsaturated compounds III*. Synthesis of α,β-unsaturated ethyl ketones by cross-hydrocarbonylation of acetylenes and ethylene with carbon monoxide and hydrogen
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Rhodium carbonyl-catalyzed cross-hydrocarbonylation of acetylenes and ethylene with carbon monoxide and hydrogen gives α,β-unsaturated ethyl ketones.Under CO (10 kg cm-2) and H2 (50 kg cm-2) at 90 deg C the reaction of diphenylacetylene with ethylene in the presence of Rh4(CO)12 catalyst gave (E)-1,2-diphenyl-1-penten-3-one (3a) in 91percent yield.Under similar conditions phenylacetylene (1d), 1-hexyne (1e), 3,3-dimethyl-1-butyne (1f), and trimethylsilylacetylene (1g) gave (E)-1-phenyl-1-penten-3-one (3d), (E)-4-nonen-3-one (3e), (E)-6,6-dimethyl-4-hepten-3-one (3f), and (E)-1-trimethylsilyl-1-penten-3-one (3g) in 76, 68, 93, and 62percent respectively.Thus, the reaction of terminal acetylenes proceeds with high stereo- and regioselectivity: the propionyl group is introduced to the less-sterically hindered acetylenic carbon atom.By comparison of the regioselectivity with that in the formation of 5-ethyl-2-(5H)-furanone (2), which is obtained in the presence of a hydrogen donor such as alcohol, these reactions are assumed to include a β-acylvinylrhodium complex as the common key intermediate.
- Hong, Pangbu,Mise, Takaya,Yamazaki, Hiroshi
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p. 129 - 140
(2007/10/02)
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- Interaction of Fischer carbene complexes of the type W(CO)5[C(OMe)R] (R = CH3, C2H5) with acetylenes
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W(CO)5[C(OMe)CH2R1] (R1 = H, CH3) reacts with PhC2R2 (R2 = Ph, CH3) in toluene at 100°C to give vinyl ethers and enones. The formation of these products can be explained by an exocyclic β-hydride elimination reaction of a metallacyclobutene intermediate.
- Macomber, David W.
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p. 1589 - 1591
(2008/10/08)
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