Conjugate additions Brpnsted base catalysts

With respect to the catalysts employed in conjugate additions, a big collection of efficient stable and environmentally friendly natural or newly designed chiral organocatalysts has already been developed. These catalysts are usually cheap to prepare and readily accessible in a range of quantities. They fall into four major classes Lewis bases, Lewis acids, Brpnsted bases, and Brpnsted acids [If]. The identification of the generic modes of activation of these catalysts has been crucial to the success of organocatalysis. 

Chiral ion pairs (B, Fig. 2.2) can be formed by deprotonation of the pronucleophile with a chiral Brpnsted base or employing an achiral base and a chiral phase-transfer catalyst. Chiral phase-transfer catalysis (PTC) [8] illustrates how ion pairing interactions can be used to carry out the enantioface discrimination in conjugate addition reactions. In both cases, the chiral cation is responsible for... 

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