Nitro-Mannich reaction and intramolecular 1,3-dipolar cycloaddition route to acylpyrrolidinones: Synthesis of a tetramic acid and (+)-laccarin

The Stereoselective Nitro-Mannich Reaction in the Synthesis of Active Pharmaceutical Ingredients and Other Biologically Active Compounds

The nitro-Mannich (aza-Henry) reaction, in which a nitroalkane and an imine react to form a β-nitroamine, is a versatile tool for target-oriented synthesis. Although the first stereoselective reaction was developed only 20 years ago, and enantioselective and diastereoselective versions for the synthesis of non-racemic compounds soon after, there are nowadays a variety of reliable methods which can be used for the synthesis of APIs and other biologically active substances. Hence many anticancer drugs, antivirals, antimicrobials, enzyme inhibitors and many more substances, containing C-N bonds, have been synthesized using this reaction. Several transition metal complexes and organocatalysts were shown to be compatible with the presence of a wide range of functional groups in these molecules, and very high levels of asymmetric induction have been achieved in some cases. The reaction has also been applied in cascade processes. The structural diversity of the products, ranging from simple heterocycles or azabicycles to complex alkaloids, iminosugars, amino acids or diamino acids and phosphonates, shows the versatility of the nitro-Mannich reaction and its potential for future developments.

Comprehension of the α-Arylation of Nitroalkanes

Background:

α-Aryl substituted nitroalkanes are important synthetic intermediates for the preparation of pharmaceutical molecules, natural products, and functional materials. Due to their scare existence in Nature, synthesis of these compounds has attracted the attention of synthetic and medicinal chemists, rendering α-arylation of nitroalkanes of an important research topic. This article summarizes the important advances of α- arylation of nitroalkanes since 1963.

Results:

After a brief introduction of the synthetic application and the reactions of nitroalkanes, this article reviewed the synthetic methods for the α-arylated aliphatic nitro compound. The amount of research on α-arylation of nitroalkanes using various arylation reagents and the discovery of elegant synthetic approaches towards such skeleton have been discussed. This review described these advances in two sections. One is the arylation of non-activated nitroalkanes, with an emphasis on the application of diverse arylation reagents; the other focuses on the arylation of activated nitroalkanes, including dinitroalkanes, trinitroalkanes, α-nitrosulfones, α-nitroesters, α-nitrotoluenes, and α-nitroketones. The synthetic application of these methods has also been presented in some cases.

Conclusion:

In this review, we described the progress of α-arylation of nitroalkanes. Although the immense amount of research on α-arylation of aliphatic nitro compounds has been achieved, many potential issues still need to be addressed, especially the asymmetric transformation and its wide application in organic synthesis.

Recent synthetic applications of α-amido sulfones as precursors of N-acylimino derivatives

α-Amido sulfones can be directly used as N-acylimine or N-acyliminium ion precursors in several synthetic processes aimed at the preparation of nitrogen containing compounds. This review collects the most relevant and practical utilizations of α-amido sulfones appeared in the literature after 2005.