Vinylogous Bronsted bases

Scheme 6.15 Enantioselective vinylogous Michael reactions catalyzed by chiral Bronsted bases.

Vinylogous Aidoi Reactions in Bronsted Base Cataiysis... 

Br0nsted Base Catalysis Including Bijunctional Catalysis 819 Table 28.7 Direct vinylogous aldol reactions in Bronsted base catalysis. 

Vinylogous Aldol Reactions in Bronsted Base Catalysis... 

The vinylogous Mannich reaction of 2 silyloxy furans and imines may also be catalyzed through chiral Brpnsted acids, as shown by Akiyama et al. [10]. Previously, Akiyama [11] and Terada [12] had independently discovered that 3,3 substituted BINOL based phosphoric acids were excellent Bronsted acids for a broad range of mainly imine addition reactions via protonation of the imines and in situ formation of chiral iminium contact ion pairs. Using the slightly modified phosphoric acid 28 as catalyst carrying additional iodine substituents in the 6,6 positions, the y amino substituted butenolides 27 were obtained in excellent enantioselectivity and variable diastereoselectivity (Table 5.4). 

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