Bifunctional phosphine-sulfonamide

The Sharpless ligand (DHQD>2AQN 45 was introduced to the asymmetric BH reaction in combination with acetic acid as co-catalyst. The ammonium salt generated in situ was proposed as a bifunctional catalyst, where the protonated amine acted as Brpnsted acid and the nonprotonated one performed as nucleophilic catalyst [99]. Besides, a simple phosphine-sulfonamide 46, synthesized readily from L-threonine, was found to be an efficient catalyst for the reaction of 7V-sulfonyl imines and (3-naphthyl acrylate to give the product in excellent enantioselectivities [100]. 

A series of bifunctional phosphine-sulfonamides have been developed as catalysts for the aza-MBH reactions. The threonine-derived candidate (200) turned out to be the most efficient (<97% ee) ... 

Figure 31.3 Novel bifunctional phosphine-sulfonamide organic catalysts 143-148 derived from natural amino acids.

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