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A simple and efficient organocatalytic enantioselective hydrophosphonylation of imines to enantiomerically enriched alpha-amino phosphonates is reported. By using 10 mol % of quinine as the catalyst in the enantioselective addition of diethyl phosphite to N-Boc protected imines, alpha-amino phosphonates are obtained in moderate to good yields and with up to 94% ee.

A novel organocatalytic approach for aza-Michael reaction of chalcones using commercial and non-expensive O-benzylhydroxylamine and a readily available organocatalyst is provided. The use of this simple protocol results in β-keto hydroxylamines in up to 60% ee, thus extending the generality of the catalytic enantioselective aza-Michael reaction.

Different malonates and beta-ketoesters can react with N-tert-butoxycarbonyl- (N-Boc) and N-benzyloxycarbonyl- (N-Cbz) protected alpha-amido sulfones in an organocatalytic asymmetric Mannich-type reaction. The reaction makes use of a simple and easily obtained phase-transfer catalyst and proceeds under very mild and user-friendly conditions. The optimised protocol avoids the preparation and the isolation of the relatively unstable N-Boc and N-Cbz imines that are generated in situ from the bench-stable alpha-amido sulfones. The corresponding Mannich bases are generally obtained in good yields and enantioselectivities, and can be readily transformed into key compounds, such as optically active beta3-amino acids in one easy step. Enantioenriched N-Boc and N-Cbz protected beta-amino acids that are suitable for peptide synthesis are also available from the Mannich adducts through simple manipulations. Control experiments showed the dual role of the enolate-catalyst ion pair in this reaction, as well as the crucial role of the presence of water to achieve high enantioselectivities.

Different malonates and beta-ketoesters can react with N-tert-butoxycarbonyl- (N-Boc) and N-benzyloxycarbonyl- (N-Cbz) protected alpha-amido sulfones in an organocatalytic asymmetric Mannich-type reaction. The reaction makes use of a simple and easily obtained phase-transfer catalyst and proceeds under very mild and user-friendly conditions. The optimised protocol avoids the preparation and the isolation of the relatively unstable N-Boc and N-Cbz imines that are generated in situ from the bench-stable alpha-amido sulfones. The corresponding Mannich bases are generally obtained in good yields and enantioselectivities, and can be readily transformed into key compounds, such as optically active beta3-amino acids in one easy step. Enantioenriched N-Boc and N-Cbz protected beta-amino acids that are suitable for peptide synthesis are also available from the Mannich adducts through simple manipulations. Control experiments showed the dual role of the enolate-catalyst ion pair in this reaction, as well as the crucial role of the presence of water to achieve high enantioselectivities.

A novel organocatalytic approach for aza-Michael reaction of chalcones using commercial and non-expensive O-benzylhydroxylamine and a readily available organocatalyst is provided. The use of this simple protocol results in β-keto hydroxylamines in up to 60% ee, thus extending the generality of the catalytic enantioselective aza-Michael reaction.

We describe a biomimetic organocatalytic enantioselective decarboxylative addition of malonic acid half thioesters to imines. This simple protocol makes use of readily available Cinchona-derived organocatalysts and nucleophiles at the carboxylate oxidation state. The resulting β-amino thioesters, being attractive precursors for the preparation of optically active β-amino acids, are formed in good yields and in up to 79 % ee. As suggested by several mechanistic insights the desired products are formed via initial formation of a thioester acetate enolate via decarboxylation of the malonic acid half thioester, followed by addition to the imine.

The aza-Henry reaction of imines with nitromethane was promoted by cinchona alkaloids and modified cinchona bases to give optically active β-nitroamines. Various N-protected imines were examined as substrates. N-Boc, N-Cbz, and N-Fmoc protected imines gave the best results in terms of chemical yields and enantioselectivities. After a careful screening of a series of chiral bases, very good enantioselectivities up to 94% ee were obtained using a cinchona-based thiourea organocatalyst under the optimized reaction conditions.

Using thioureas as H-bonding organocatalysts, nitro­alkenes can be activated for the conjugate addition of hydrazones as neutral nucleophiles. Formaldehyde derivatives react at the azo­methine carbon as expected, whereas hydrazones from enolizable aldehydes behave as ene-hydrazines and react at the α-carbon ­instead. Ionic liquids were found to decrease the reaction times ­considerably compared to commonly used solvents, whereas alternative activation by Lewis acids resulted in decomposition of ­reactants.

A study into the use of a chiral phase-transfer catalyst in conjunction with acetone cyanohydrin to effect the enantioselective formation of alpha-amino nitriles from alpha-amido sulfones is described. This novel catalytic asymmetric Strecker reaction is analyzed with regard to the possible mechanistic basis.

The highly enantioselective reaction between in situ generated, Cbz-protected azomethines and malonates in the presence of 150 mol % of potassium carbonate (50 % w/w) and 1 mol % of quinine-derived quaternary ammonium bromides as phase-transfer organocatalysts has been developed. This study reports a novel approach for the asymmetric Mannich-type reaction and a wide range of azomethines, including those derived from enolizable aldehydes, is tolerated by the present system. The adducts, obtained in excellent yields with ee up to 98 %, are suitable precursors of optically pure β-amino acids.

A general approach to the catalytic asymmetric aza‐Henry reaction has been developed. The combination of a commercially available phase‐transfer catalyst (PTC) with a base is able to promote the in situ formation of N‐carbamoyl imines from α‐amido sulfones and activate nitromethane towards the asymmetric addition reaction, thus furnishing N‐carbamoyl‐protected β‐nitroamines in good yields and with up to 98 % ee (see scheme; PG=protecting group).