Evaluating β-amino acids as enantioselective organocatalysts of the Hajos–Parrish–Eder–Sauer–Wiechert reaction
作者:Stephen G. Davies、Angela J. Russell、Ruth L. Sheppard、Andrew D. Smith、James E. Thomson
DOI:10.1039/b711171a
日期:——
A systematic study of the effect of substitution within the β-amino acid framework indicates that both β2- and β3-amino acids catalyse the HajosâParrishâEderâSauerâWiechert reaction with poor to reasonable levels of enantioselectivity. These results led to the evaluation of the conformationally constrained β-amino acid (1R,2S)-cispentacin, which catalyses the HajosâParrishâEderâSauerâWiechert reaction with comparable or higher levels of enantioselectivity to L-proline.
<i>N</i>-Tosyl-(<i>S</i><sub>a</sub>)-binam-<scp>l</scp>-prolinamide as Highly Efficient Bifunctional Organocatalyst for the General Enantioselective Solvent-Free Aldol Reaction
N-Tosyl-(S a)-binam-l-prolinamide (5 mol%) and benzoic acid (1 mol%) were used as catalysts in the enantioselective direct aldol reaction between different ketones and aldehydes under solvent-free conditions in the presence or absence of water. Under these reaction conditions it was possible to reduce the amount of required ketone to two equivalents to give the corresponding aldol products with high yields, regio-, diastereo- and enantioselectivities. The aldol reaction between aldehydes or the intramolecular aldol reaction can be also performed with excellent results.