Development of Asymmetric Reactions of Diazo Carbonyl Compounds in the Presence of Metal-Catalysts having Axial Chirality

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In the presence of 10 mol % of rare earthmetal triflate as catalyst, the reaction of pheriyldiazoacetate with alcohols proceeded smoothly to give desired α, α-substituted products in high yield. Moderate diastereoselectivity was obtained in the reaction of l-menthyl phenyldiazoacetate. The use of the catalysts, which were prepared by mixing the ligands having axial chirality such as binaphthol and binaphthyldiimine derivatives with rare earth metal triflates, did not show satisfactory results in terms of selectivity and chemical yield.Stereocontrol by using Lewis acid in the reaction of 2-benzopyrylium-4-olate, which was generated by Rh_2( OAc )_4-catalyzed decomposition of o-methoxycarbonyl-α-diazbacetophenone, was also investigated. In the reaction with N-substituted maleimide under reflux in benzene showed exo-selectivity, while the reaction in the presence of 10 mol % of Yb( OTf )_3 in CH_2Cl_2 at room temperature proceed with high endo-slectivity. On the other hand, addition of 10 mol % of Yb( OTf )_3 was quite effective in obtaining high exo-selectiyity in the reaction with benzaldehyde, p-substituted benzaldehyde, and benzyloxyacetoaldehyde in Et_2O or CH_2Cl_2. We also found that the use of 10 mol % of lanthanide tris( S )-1,1'-binaphthyl-2,2'-diyl phosphate, known to be an effective catalyst for hetero Diels-Alder reaction of Danishefsky's diene, showed moderate enantioselectivity (endo: 20 - 52 % ee), although almost no diastereoselectivity was observed. Furthermore, in the presence of the chiral catalyst, which was prepared from 2,6-bis[( 4S )-( - )-isopropyl-2-oxazolin-2-yl]pyridine and Sc( OTf )_3, enantioselectivity of the endo-product showed 86 % ee ( endo : exo = 76 : 24 ). To the best of knowledge, this is the first example of asymmetric induction found in the chiral Lewis acid-catalyzed cycloaddition reaction of a carbonyl ylide.