Bifunctional organocatalysts are increasingly important for the discovery of new asymmetric reactions. Herein we report a new class of bifunctional organocatalysts incorporating triaryliminophosphoranes and a H-bond donor group (Figure 1a). We have shown that triaryliminophosphoranes have comparable basicities to other organic superbases. The catalysts can be synthesized on gram scale.We have applied the catalysts to the first general organocatalytic enantioselective nitro-Mannich reaction of nitromethane to ketimines. The reaction was applied to 17 examples with up to 97% yield and up to 95% ee (Figure 1b). The reaction was also performed on a 10 g preparative scale with 1% catalyst loading. (Figure 1c).Furthermore, the catalysts have outperformed existing tertiary amine bifunctional organocatalysts in a known challenging Michael addition by a rate increase of 1300 under identical conditions with maintained diastereoselectivity and enantiocontrol. As a further demonstration of the broad applicability of the new family of superbasic organocatalysts, a second generation BIMP catalyst was applied to the addition of alkyl thiols to a-substituted, a,� unsaturated esters. The reaction was applied to 20 substrates with yields up to 99% and ee up to 97% with catalyst loadings down to 0.05mol%.

New class of highly active and tunable bifunctional organocatalysts for asymmetric synthesis (BIMP)

248th National Meeting (2014)

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