Organocatalytic Reactions Enabled by N-Heterocyclic Carbenes.

Bull. Chem. Soc. Jpn. への投稿のすすめ

The aim of this review article on recent developments of mechanochemistry (nowadays established as a part of chemistry) is to provide a comprehensive overview of advances achieved in the field of atomistic processes, phase transformations, simple and multicomponent nanosystems and peculiarities of mechanochemical reactions. Industrial aspects with successful penetration into fields like materials engineering, heterogeneous catalysis and extractive metallurgy are also reviewed. The hallmarks of mechanochemistry include influencing reactivity of solids by the presence of solid-state defects, interphases and relaxation phenomena, enabling processes to take place under non-equilibrium conditions, creating a well-crystallized core of nanoparticles with disordered near-surface shell regions and performing simple dry time-convenient one-step syntheses. Underlying these hallmarks are technological consequences like preparing new nanomaterials with the desired properties or producing these materials in a reproducible way with high yield and under simple and easy operating conditions. The last but not least hallmark is enabling work under environmentally friendly and essentially waste-free conditions (822 references).

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Hallmarks of mechanochemistry: From nanoparticles to technology

Oxindoles and spirooxindoles are important synthetic targets that are often considered to be prevalidated with respect to their biological activity and applications for pharmaceutical lead discovery This review features efficient strategies for the enantioselective synthesis of spirocyclic oxindoles, focusing on reports in 2010 and 2011 Although enantioselective synthesis remains an ongoing challenge, exciting recent advances in this area feature spirooxindoles with greater complexity, up to eight stereogenic centers, more practical synthetic methods, and new catalytic activation strategies Developments in catalyst systems and reaction conditions have shown that many reactions can be optimized to control selectivity and provide access to isomeric products, which are important for biological testing This review is organized based on two primary disconnection strategies, and then further subdivided into the type and ring size of the spirocycle that is generated Strategies are also compared for the synthesis of non-spirocyclic 3,3′-disubstituted oxindoles

Strategies for the enantioselective synthesis of spirooxindoles.

In recent years, organocatalysis has enhanced its importance as a tool for the synthesis of enantiomerically enriched compounds. Among the candidates for organocatalysis, the construction of asymmetric quaternary carbons is regarded as a challenging problem in organic synthesis. In particular, 3,3′-disubstituted oxindoles have one or more asymmetric quaternary carbon atoms and they represent a large family of bioactive compounds and synthetic derivatives that mimicry natural products. Therefore they are good targets for drug candidates and in the last two years many papers have appeared on organocatalytic methods for the synthesis of 3,3′-disubstituted oxindoles. Moreover, in the last few years 2-substituted and 2,2′-disubtituted 3-indolinones have also attracted the interest of chemists. This review aims to cover the literature on these topics from its origin to the end of 2011.

Recent advances in organocatalytic methods for the synthesis of disubstituted 2- and 3-indolinones

Organocatalytic Carbon–Sulfur Bond-Forming Reactions

Organocatalytic domino/cascade reactions provide a convenient method for the construction of complex molecular structures bearing multiple stereocenters in a highly stereoselective fashion. Among various organocatalysts, bifunctional squaramides have emerged as powerful hydrogen-bonding catalysts for promoting a wide array of useful asymmetric organocascade sequences. Higher activity and ease of preparation make these catalysts excellent alternatives for thiourea-based organocatalysts. This review highlights the advances in the rapidly growing field of amine-squaramide-catalyzed domino/cascade reactions and their mode of action.

Bifunctional Amine‐Squaramides: Powerful Hydrogen‐Bonding Organocatalysts for Asymmetric Domino/Cascade Reactions

Asymmetric synthesis of pyrazoles and pyrazolones employing the reactivity of pyrazolin-5-one derivatives

N-heterocyclic carbene (NHC) catalysis has emerged as a powerful strategy in organic synthesis. In recent years a number of reviews have been published on NHC-catalyzed transformations involving Breslow intermediates, acyl azoliums, α,β-unsaturated acyl azoliums, homoenolate equivalents, and azolium enolates. However, the azolium dienolate intermediates generated by NHCs have been employed in asymmetric synthesis only very recently, especially in cycloadditions dealing with remote functionalization. This Minireview highlights all the developments and the new advances in NHC-catalyzed asymmetric cycloaddition reactions involving azolium dienolate intermediates.

N-Heterocyclic Carbene Catalysis via Azolium Dienolates: An Efficient Strategy for Remote Enantioselective Functionalizations.

3-Amino-2-oxindoles bearing tetra-substituted stereocenter are very important constituents of many bioactive and pharmaceutical agents. In the last few years, asymmetric organocatalysis emerged as an excellent approach for the synthesis of optically active 3-substituted-3-amino-2-oxindoles. This review describes the various organocatalytic enantioselective strategies for the synthesis of 3-substituted 3-amino-2-oxindole frameworks.

Pankaj Chauhan

Papers

Organocatalytic Carbon–Sulfur Bond-Forming Reactions

Bifunctional Amine‐Squaramides: Powerful Hydrogen‐Bonding Organocatalysts for Asymmetric Domino/Cascade Reactions

Asymmetric synthesis of pyrazoles and pyrazolones employing the reactivity of pyrazolin-5-one derivatives

N-Heterocyclic Carbene Catalysis via Azolium Dienolates: An Efficient Strategy for Remote Enantioselective Functionalizations.

Organocatalytic asymmetric synthesis of 3-amino-2-oxindole derivatives bearing a tetra-substituted stereocenter