Squaramide-catalyzed diastereo- and enantioselective Michael addition of 3-substituted oxindoles to nitroalkenes
作者:Wen Yang、Jingsi Wang、Da-Ming Du
DOI:10.1016/j.tetasy.2012.06.018
日期:2012.7
An efficient diastereo- and enantioselectiveMichaeladdition of 3-substituted oxindoles onto nitroalkenes catalyzed by a bifunctional chiral squaramide catalyst has been developed. This organocatalytic reaction with 2 mol % of catalyst proceeded smoothly to afford 3,3-disubstituted oxindoles in high yields with good diastereoselectivities and enantioselectivities (up to 98:2 dr, 88% ee).
Michael Addition of N-Unprotected 2-Oxindoles to Nitrostyrene Catalyzed by Bifunctional Tertiary Amines: Crucial Role of Dispersion Interactions
作者:Christoph Reiter、Sònia López-Molina、Bernhard Schmid、Christian Neiss、Andreas Görling、Svetlana B. Tsogoeva
DOI:10.1002/cctc.201301052
日期:2014.3.5
Bifunctional thiourea‐ or sulfonamide‐derived tertiary aminescatalyze the enantioselective nitro‐Michaeladdition of N‐unprotected 3‐substituted 2‐oxindoles to nitrostyrene in up to 99 % yields, 94:6 er, and 87:13 dr. Overcoming the necessity to introduce and remove activating or protecting groups at the nitrogen moiety leads to a reduction of energy use, costs, and waste. Transition‐state geometries