Mannich-Type Reactions Using PSSEE

PSSEEs react with imines in the presence of a Lewis acid to afford /3-amino thioesters, which can be reduced to give amino alcohols (Table 6) [85a], In this reaction, although typical Lewis acids such as TiCU, SnCU, and BF3 OEt2 gave poor results, a catalytic amount of Sc(OTf)3 or Hf(OTf)4 gave better results. This process provides a convenient method for the construction of an amino alcohol library. 

Lewis acid (mol %) Yield (%) Lewis acid (mol %) Yield (%) 

In the solid phase, Sc(OTf)3 also effectively catalyzed Mannich-type three-component reactions of aldehydes, amines, and PSSEEs to afford polymer-supported /3-amino thioesters (Eq. 22). Reductive cleavage from the supports gave the amino alcohols in good to high yields [85b]. /3-Amino acid and /3-lactam libraries are also constructed according by this method (Eq. 23). 

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