102(P-20) 光学活性なサレン錯体触媒を用いるキラルビルディングブロックの効率的不斉合成(ポスター発表の部)

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Second-generation metallosalen complexes show versatile and highly efficient asymmetric catalysis such as transfer of oxene, nitrene and carbene species and Lewis acidity. Taking advantage of their asymmetric catalysis, we developed new methodologies for enantioselective synthese of 2-substituted pyranones, sulfoximides, cis-disubstituted cyclopropanes, and optically active secondary alcohols that serve as useful chiral building blocks for organic synthesis. 1. Asymmetric hetero Diels-Alder reaction Hetero Diels-Alder reaction of Danishefsky's diene with various aldehydes was carried out in a highly enantioselective manner (93-97% ee, at 0℃) by using appropriate second-generation cationic (aR,S)- or (aR,R)-(salen)-manganese or -chromium complex as the catalyst, affording 2-substituted pyrones. Both aliphatic and aromatic aldehydes can be used as substrates irrespective of presence or absence of precoordinating functional group(s). 2. Enantioselective imidation of alkyl aryl sufides Enantioselective imidation of alkyl aryl sufides was examined by using (aR,S)-8 or (aR,R)-(salen)manganese complex 9 as a catalyst with PhI=NTs as the nitrene source. The imidation of sulfides bearing no precoordinating functional group was found to be effected in the presence of NMO by using (aR,R)-8 as the catalyst (up to 89% ee), while sulfides bearing electron-withdrawing nitro group such as methyl 2-nitrophenyl sulfide by using (aR,S)-9 as the catalyst in the absence of donor ligand. 3. Cis-selective asymmetric cyclopropanation Reaction of styrene derivatives and t-butyl α-diazoacetate using (aR,R)-(salen)cobalt(II) complex 11 as a catalyst in the presence of N-methylimdazole gave the corresponding cyclopropanecarboxylates with excellent enantio- (up to 99% ee) and high cis-selectivity (98%) together with good chemical yield. 4. Catalytic asymmetric aerobic oxidation Optically active (salen)ruthenium complex 10 was found to be an efficient catalyst for aerobic oxidation of racemic secondary alcohols under irradiation with a halogen or fluorescent lamp. The reaction proceeded with good enantiomer-differentiation (K_<rel>=11-20).
天然有機化合物討論会の論文
2000-10-01

102(P-20) 光学活性なサレン錯体触媒を用いるキラルビルディングブロックの効率的不斉合成(ポスター発表の部)

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