Proline was a benchmark in organocatalysis, nevertheless, it has serious limitations in selectivity, reaction rates, catalyst loads, and solubility in organic solvents. This lead to the development of many aminocatalysts with tuned reactivity and selectivity. Many of these catalysts are obtained by conventional synthesis from L-proline (stepwise approach and purifications) (Figure 1a). We propose that tetrabutyl ammonium prolinate can be complexed with different 1,3-disubstituted thioureas and as result give a variety of catalysts can be obtained easily (Figure 1b). As a model reaction we chose the Michael addition of cyclohexanone to nitrostyrene. We found that different thioureas afforded different yields and selectivities with d.r. between 90:10 to 97:3. Thiourea with 9-fluorenyl gave the best result with benzoic acid and after optimization with a variety of acids the enantioselectivity raised to 97:3 with (S)-mandelic acid. List, B.; Pojarliev, P.; Martin, H. J. Org. Lett. 2001 , 3, 2423.Enders, D.; Seki, A. Synlett 2002 , 26.

Aminocatalysis based upon supramolecular prolinate-thiourea aggregates

248th National Meeting (2014)

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