Amine nucleophilic addition to nitroalkene as a new practical approach for the synthesis of fully substituted isoxazoline-N-oxide

1,3-Difunctionalization of β-Alkyl Nitroalkenes via Combination of Lewis Base Catalysis and Radical Oxidation

Upon treatment with a Lewis base catalyst, β-alkyl-substituted nitroalkenes could be readily converted into allylic nitro compounds. Examples of either C-1 or C-3 functionalization methods have been reported through nitro-elimination, giving alkene products. In this work, successful 1,3-difunctionalization was achieved through a synergetic Lewis base catalysis and TBHP radical oxidation, giving vinylic alkoxyamines in good to excellent yields. This work further extended the general synthetic application of β-alkyl nitroalkenes.

Nitroacetic Esters in the Regioselective Synthesis of Isoxazole-3,5-dicarboxylic Acid Derivatives

An efficient and high-yielding strategy to prepare "unsymmetrical" 4-aryl-isoxazol-3,5-dicarboxylic acid derivatives from nitroacetic esters and aromatic aldehydes has been developed. The strategy is based on the isolation and usage of the previously missed intermediate of the Dornow reaction-5-hydroxy-6-oxo-4-aryl-6H-1,2-oxazine-3-carboxylates. In addition, the mechanism of the Dornow reaction was partially revised.

Catalytic asymmetric (4 + 1) annulation of nitroalkenes with allylic acetates: stereoselective synthesis of isoxazoline N-oxides

An asymmetric (4 + 1) annulation of α-nitro cinnamates with Morita-Baylis-Hillman (MBH) acetates catalyzed by α-isocupreine is reported. It provides chiral isoxazoline N-oxides in moderate to good yields with 88-99% ee, and represents the first catalytic asymmetric (4 + 1) annulation of activated nitroalkenes with in situ generated ammonium ylides. It also affords a practical and efficient access to chiral isoxazoline N-oxides.

Asymmetric synthesis of substituted NH-piperidines from chiral amines

Previously, we reported an efficient asymmetric synthesis of substituted piperidines through an exocyclic chirality induced nitroalkene/amine/enone (NAE) condensation reaction. An effective protecting group strategy was developed herein to achieve enantiopure piperidines (yields up to 92%) with complete chirality retention (ee > 95%). A simple derivatization of the obtained piperidines gave thiourea catalysts, indicating the strong potential of this method for producing new amine-based dual functional organocatalysts for future development.

A versatile and efficient approach for the synthesis of chiral 1,3-nitroamines and 1,3-diamines via conjugate addition to new (S,E)-γ-aminated nitroalkenes derived from L-α-amino acids

New chiral (S,E)-γ-N,N-dibenzylated nitroalkenes 2a-c were synthesized from natural L-(α)-amino acids in five steps with overall yields of 68-88%. The conjugate addition of hydride, methoxide, nitronate and azide nucleophiles to 2a-c led to the corresponding chiral 1,3-nitroamines in 74-90% yield. The conjugate addition of cyanide anion to 2a,b was followed by HNO2 elimination affording chiral aminated acrylonitriles (73-98%). On the other hand, the azide anion reacted with 2a, in acetonitrile, via a [3 + 2]-cycloaddition in which HNO2 was lost, providing the corresponding 1,2,3-triazole derivative. Direct reduction of 1,3-nitroamine derivatives 9a,b produced the corresponding 1,3-diamines in good yields.