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).
A simple alkylthiourea was found to be an effective catalyst for the Michaeladditionreaction of 3-substitutedoxindole to nitroolefins. A number of 3,3′-substituted oxindole derivatives, which have two vicinal quaternary-tertiary chiral centers were synthesized with up to 99% yield, 19:1 dr and 98% ee.
Organocatalytic Michael addition of unprotected 3-substituted oxindoles to nitroolefins
作者:Miao Ding、Feng Zhou、Zi-Qing Qian、Jian Zhou
DOI:10.1039/c004037a
日期:——
Quinidine was found to catalyze the Michaeladdition of unprotected 3-substitutedoxindoles to nitroolefins in excellent yield and moderate to good diastereoselectivity. Bifunctional quinidine derived thioureacatalyst 10 could catalyze this reaction to afford the major diastereomer in up to 85% ee.
Chiral auxiliaries: A new neutralreaction system with lipophilic [18]crown‐6 derivatives and with an aqueous KCl solution has been successfully utilized for several conjugate‐addition reactions (see scheme). The ring size, lipophilicity of the crown ether, and the presence of water are crucial to promote the reaction efficiently. The reaction system can also be applied to asymmetric conjugate addition