Study on Novel Carboxylation Reactions Using CO2 as a C1 Sourece

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In this study, we have succeeded a novel one-pot process for alpha-amino acid synthesis from imine precursors using Me3SiSnBu3 or PhMe2SiBpin in the presence of CsF. Also, a catalytic enantioselective silylation of N-t-butylsulfonylimines using a copper-diamine complex was realized, and the resulting optically active alpha-amino silanes could be carboxylated under a CO2 atmosphere (1 atm) to afford the corresponding alpha-amino acids in a stereoretentive manner. This two-step sequence provides a new synthetic protocol for optically active alpha-amino acids from gaseous CO2. Furthermore, we also found that N-acyl-N,O-acetals were successfully converted into the corresponding alpha-amino acids under 1 atm of CO2 atmosphere in high yields in the presence of Mn powder, BF3-Et2O, and LiCl. The LiCl additive is necessary in order to increase the solubility and the nucleophilicity of an organomanganese intermediate.