Abstract
The enantioselective conjugate addition reaction of 3-aryl-substituted oxindoles with methyl vinyl ketone promoted by binaphthyl-modified bifunctional organocatalysts was investigated. The corresponding Michael adducts, containing a quaternary center at the C3-position of the oxindoles, were generally obtained in high yields with excellent enantioselectivities (up to 91% ee).
Highlights
Oxindole structures exist in a large number of natural and biologically active molecules [1–4]
Discovering various electrophiles to react with 3-substituted oxindoles for the synthesis of diversely structured 3,3-disubstituted oxindoles is still strongly desired
Several groups have reported the Molecules 2012, 17 enantioselective conjugate addition reactions of 3-substituted oxindoles to vinyl ketones catalyzed by organocatalysts, phase-transfer catalyst, and chiral calcium phosphate [34–38]
Summary
Oxindole structures exist in a large number of natural and biologically active molecules [1–4]. Oxindole scaffolds bearing a quaternary stereocenter at the 3-position are a versatile structural motif found in a variety of biologically and pharmaceutically active natural products and utilized as building blocks for indole alkaloid synthesis [5]. Several methods for their asymmetric formation and transformation are of considerable interest. Several groups have reported the Molecules 2012, 17 enantioselective conjugate addition reactions of 3-substituted oxindoles to vinyl ketones catalyzed by organocatalysts, phase-transfer catalyst, and chiral calcium phosphate [34–38]. The development of alternative catalysts for the catalytic enantioselective conjugate addition reaction of 3-substituted oxindoles to vinyl ketones would be highly desirable
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