A cationic rhodium(I)/Segphos complex catalyzes a [2 + 2 + 2] cycloaddition of internal 1,6-diynes with a phosphonate- or ester-substituted 1,3-butadiyne leading to C(2)-symmetric axially chiral biaryl diphosphonates or dicarboxylates, respectively, in high yields with outstanding ee's. The use of a phosphonate- or ester-substituted 1,3-butadiyne as a cycloaddition partner and Segphos as a ligand is crucial for the success of this transformation.
Axially chiral hydroxy carboxylic acid derivatives were successfully synthesized with high yields and ee values by the cationic rhodium(I)/axially chiral biaryl bisphosphine complex-catalyzed enantioselective [2 + 2 + 2] cycloaddition. Axially chiral hydroxy and dihydroxy carboxylic acid derivatives, bearing the aryl group at the ortho-position of the alkoxycarbonyl group, were also synthesized with high regio- and enantioselectivity.
Enantioselective Synthesis of Axially Chiral Hydroxy Carboxylic Acid Derivatives by Rhodium-Catalyzed [2 + 2 + 2] Cycloaddition. -The Rh-catalyzed reaction of 2-methoxynaphthalene substituted propynoates with 1,6-and 1,7-diynes is found to provide biaryls and teraryls in good yields with high regio-and enantioselectivity. The 2-methoxynaphthalene moiety is essential to achieve high enantioselectivity. -(OGAKI, S.; SHIBATA, Y.; NOGUCHI, K.; TANAKA*, K.; J. Org. Chem. 76 (2011Chem. 76 ( ) 6, 1926Chem. 76 ( -1929Chem. 76 ( , http://dx.doi.org/10.1021 Dep. Appl. Chem., Grad. Sch. Eng., Tokyo Univ. Agric. Technol., Koganei, Tokyo 184, Japan; Eng.) -Jannicke 24-028
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