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In the investigation of efficient chemical transformations, the carbon-carbon bond-forming reactions play an outstanding role. In this context, organocatalytic processes have achieved considerable attention. 1 Beside their facile reaction course, selectivity, and environmental friendliness, new synthetic strategies are made possible. Particularly, the inversion of the classical reactivity (Umpolung) opens up new synthetic pathways. 2 In nature, the coenzyme thiamine (vitamin B1), a natural thiazolium salt, utilizes a catalytic variant of this concept in biochemical processes as nucleophilic acylations. 3 The catalytically active species is a nucleophilic carbene. 4

Organocatalysis by N-Heterocyclic Carbenes

Asymmetric enamine catalysis.

The applications of copper (Cu) and Cu-based nanoparticles, which are based on the earth-abundant and inexpensive copper metal, have generated a great deal of interest in recent years, especially in the field of catalysis. The possible modification of the chemical and physical properties of these nanoparticles using different synthetic strategies and conditions and/or via postsynthetic chemical treatments has been largely responsible for the rapid growth of interest in these nanomaterials and their applications in catalysis. In addition, the design and development of novel support and/or multimetallic systems (e.g., alloys, etc.) has also made significant contributions to the field. In this comprehensive review, we report different synthetic approaches to Cu and Cu-based nanoparticles (metallic copper, copper oxides, and hybrid copper nanostructures) and copper nanoparticles immobilized into or supported on various support materials (SiO2, magnetic support materials, etc.), along with their applications i...

http://pubs.acs.org/doi/pdfplus/10.1021/acs.chemrev.5b00482

Cu and Cu-Based Nanoparticles: Synthesis and Applications in Catalysis.

8.4.5. Nitromercuration Reactions 3878 9. Hydroamination of Alkenes and Alkynes under Microwave Irradiation 3878 * To whom correspondence should be addressed. Phone: +49 241 8

Hydroamination: direct addition of amines to alkenes and alkynes.

This review delineates the scope and limitations of the conjugate addition of homochiral lithium amides to act as homochiral ammonia equivalents for the asymmetric synthesis of a range of β-amino carboxylic acid derivatives and its widespread applications in synthesis.

The conjugate addition of enantiomerically pure lithium amides as homochiral ammonia equivalents: scope, limitations and synthetic applications

Organocatalysis represents a synthetic paradigm that has grown exponentially in popularity over the last decade, arguably becoming one of the most desired synthetic methods for the creation of enantiomerically enriched products. Within this field the use of N-heterocyclic carbenes (NHCs) has seen appreciable research activity with the realisation of many novel reaction types. This review provides a comprehensive account of recent advances in the generation and reactivity of azolium enolates with exclusive focus on those processes rendered asymmetric through the use of chiral NHCs. 1	Introduction: NHCs in Organocatalysis 1.1	Azolium Enolates 2	Azolium Enolate Generation via Ketenes 2.1	Asymmetric Formal [2+2] Cycloadditions 2.2	Asymmetric Formal [3+2] Cycloadditions 2.3	Asymmetric Formal [4+2] Cycloadditions 2.4	Asymmetric Protonation and Halogenation 3	Azolium Enolate Generation via α-Functionalised Aldehydes 4	Azolium Enolate Generation via Enals 5	Activated Esters as Azolium Enolate Precursors 6	Conclusions and Outlook

NHCs in Asymmetric Organocatalysis: Recent Advances in Azolium Enolate Generation and Reactivity

N-Heterocyclic carbenes promote the formal [2+2] cycloaddition of ketenes with N-tosyl imines to give the corresponding β-lactams in good to excellent isolated yields; chiral NHCs give β-lactams in high e.e. after crystallisation.

/pdf/n-heterocyclic-carbene-catalysed-b-lactam-synthesis-1a7perhkk7.pdf

N-Heterocyclic carbene catalysed β-lactam synthesis

Tetramisole promotes the catalytic asymmetric intramolecular Michael addition−lactonization of a variety of enone acids, giving carbo- and heterocyclic products with high diastereo- and enantiocontrol (up to 99:1 dr, up to 99% ee) that are readily derivatized to afford functionalized indene and dihydrobenzofuran carboxylates. Chiral isothioureas also promote the catalytic asymmetric intermolecular Michael addition−lactonization of arylacetic acids and α-keto-β,γ-unsaturated esters, giving anti-dihydropyranones with high diastereo- and enantiocontrol (up to 98:2 dr, up to 99% ee).

Andrew D. Smith

Papers

The conjugate addition of enantiomerically pure lithium amides as homochiral ammonia equivalents: scope, limitations and synthetic applications

NHCs in Asymmetric Organocatalysis: Recent Advances in Azolium Enolate Generation and Reactivity

N-Heterocyclic carbene catalysed β-lactam synthesis

Organocatalytic functionalization of carboxylic acids: isothiourea-catalyzed asymmetric intra- and intermolecular Michael addition--lactonizations.

Isothiourea-catalyzed enantioselective carboxy group transfer.