Catalytic Carbon-Carbon Bond-Forming Reactions of Weakly Acidic Carbon Pronucleophiles Using Strong Brønsted Bases as Catalysts

Catalytic carbon-carbon bond-forming reactions of weakly acidic carbon pronucleophiles with N-aryl imines, α,β-unsaturated amides, and others under proton-transfer conditions were developed by designing strongly basic reaction intermediates known as product bases. The reactions proceed smoothly in the presence of a catalytic amount of strong base such as KH or alkaline metal amides. Modification of the metal cations by using chiral macrocyclic crown ethers allowed catalytic asymmetric 1,4-addition reactions to proceed with high enantioselectivities. This concept can be applied to Brønsted-base-catalyzed reactions of a wide range of weakly acidic carbon pronucleophiles.

Catalyst free decarboxylative trichloromethylation of aldimines

A catalyst free decarboxylative trichloromethylation of imines to afford different trichloromethyl sulfonyl and sulfinyl amines has been presented.

Direct anti-selective catalytic asymmetric Mannich-type reactions of alpha-ketoanilides for the synthesis of gamma-amino amides and azetidine-2-amides

Breaking with convention: A homodinuclear nickel complex derived from a biphenyldiamine-based Schiff base catalyzed an anti-selective Mannich-type reaction of alpha-ketoanilides (see scheme) to afford unique building blocks for the synthesis of azetidine-2-amides and alpha-hydroxy gamma-amino amides. This approach stands in contrast to conventional Mannich-type reactions for the synthesis of beta-amino carbonyl compounds. o-Ns = o-nitrobenzenesulfonyl.

Organocatalytic Asymmetric Mannich Reactions withN-Boc andN-Cbz Protected α-Amido Sulfones (Boc:tert-Butoxycarbonyl, Cbz: Benzyloxycarbonyl)

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.