Cinchonidine thiourea catalysts

In 2005, Chen and coworkers found that the epi-cinchonidine/cinchonine-derived thiourea catalysts, 79a,b, can serve as highly active promoters of the Michael addition ofthiophenol to the a,P-unsaturated imide 80 however, the reaction proceeded with low enantioselectivity (up to 17% ee) (Scheme 9.28) [22]. 

The extension of the thiourea-tertiary amine concept to the cinchona alkaloids was reported by several groups independently in 2005. The general usefulness of cinchona alkaloids as bifunctional catalysts was recognized by several groups even before this date [9]. The focus herein is on (thio)urea and squaramide catalysts since they are prototypes of more efficient catalysts. The Chen and the Dixon groups screened cinchonine and cinchonidine-derived thiourea catalysts for conjugate... 

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