A tandem Mannich-Michael reaction catalyzed by modularly designed organocatalysts
A diastereodivergent tandem Mannich-Michael reaction between an α-imino ester with 7-oxo-5-enals was achieved by using modularly designed organocatalyst (MDOs), which were self-assembled from in situ in the reaction media from á-amino acids and cinchona alkaloid derivatives. The tandem Mannich-Michael reaction generated substituted pipecolic acid derivatives. Using pseudo-diastereomeric and pseudo-enantiomeric MDOs, two diastereomers of the tandem Mannich-Michael reaction products as well as their enantiomers may be obtained in good yields, high diastereomeric ratios, and excellent ee values. The all cis -diastereomer of the tandem Mannich-Michael reaction product also undergo further cyclization under the reaction conditions to give azabicyclo[2.2.2]octanes.