Novel pyrrolidine-aminobenzimidazole bifunctional organocatalysts for asymmetric nitro-Michael reactions in brine

A new family of bifunctional organocatalysts with conformationally rigid H-bond donors was successfully synthesized and applied to the aqueous phase Michael reactions of cyclohexanone with nitroolefins. The corresponding products were obtained with high enantioselectivities (up to 99% ee) and diastereoselectivies (up to 99/1 dr) in the presence of a slight excess of Michael donors in brine at room temperature.

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(S)-N-(1H-Benzo[d]imidazol-2-yl)pyrrolidine-2-carboxamideC12H14N4O[α]D20=-15.2 (c 0.52, CH3OH)Source of chirality: prolineAbsolute configuration: (S)

(S)-N-(Pyrrolidin-2-ylmethyl)-1H-benzo[d]imidazol-2-amine dihydrochlorideC12H18Cl2N4[α]D20=-16.3 (c 0.30, CH3OH)Source of chirality: prolineAbsolute configuration: (S)

(S)-N-(Pyrrolidin-2-ylmethyl)-1H-perimidin-2-amine ditrifluoroacetateC20H20 F6N4O4[α]D20=-9.6 (c 0.22, CH3OH)Source of chirality: prolineAbsolute configuration: (S)

(S,Z)-1,2-Diphenyl-3-(pyrrolidin-2-ylmethyl)guanidine ditrifluoroacetateC2H24F6N4O4[α]D20=-6.1 (c 0.35, CH3OH)Source of chirality: prolineAbsolute configuration: (S)