Complete Field Guide to Asymmetric BINOL-Phosphate Derived Brønsted Acid and Metal Catalysis: History and Classification by Mode of Activation; Brønsted Acidity, Hydrogen Bonding, Ion Pairing, and Metal Phosphates

Chiral phosphoric acids derived from axially chiral biar- yls and related chiral Bronsted acids have emerged as an attractive and widely applicable class of enantioselective organocatalysts for a variety of organic transformations. This review focuses on recent achievements in the development of enantioselective transforma- tions using these axially chiral phosphoric acids and their analogues as chiral Bronsted acid catalysts. The contents are arranged accord- ing to the specific types of carbon-carbon bond-forming reactions, followed by carbon-heteroatom bond-forming reactions and func- tional group transformations, including reduction and oxidation. Further applications to combined phosphoric acid and metal com- plex catalytic systems and new aspects in the development of chiral Bronsted acid catalysts are also highlighted.

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Chiral Phosphoric Acids asVersatile Catalysts for Enantioselective Transformations

Multicomponent reactions (MCRs) receive increasing attention because they address both diversity and complexity in organic synthesis. Thus, in principle diverse sets of relatively complex structures can be generated from simple starting materials in a single reaction step. The ever increasing need for optically pure compounds for pharmaceutical and agricultural applications as well as for catalysis promotes the development of asymmetric multicomponent reactions. In recent years, asymmetric multicomponent reactions have been applied to the total synthesis of various enantiopure natural products and commercial drugs, reducing the number of required reaction steps significantly. Although many developments in diastereoselective MCRs have been reported, the field of catalytic enantioselective MCRs has just started to blossom. This critical review describes developments in both diastereoselective and catalytic enantioselective multicomponent reactions since 2004. Significantly broadened scopes, new techniques, more environmentally benign methods and entirely novel MCRs reflect the increasingly inventive paths that synthetic chemist follow in this field. Until recently, enantioselective transition metal-catalyzed MCRs represented the majority of catalytic enantioselective MCRs. However, metal contamination is highly undesirable for drug synthesis. The emergence of organocatalysis greatly influences the quest for new asymmetric MCRs.

Recent developments in asymmetric multicomponent reactions.

Although known for over 90 years, only in the past two decades has the chemistry of diboron(4) compounds been extensively explored. Many interesting structural features and reaction patterns have emerged, and more importantly, these compounds now feature prominently in both metal-catalyzed and metal-free methodologies for the formation of B–C bonds and other processes.

Diboron(4) Compounds: From Structural Curiosity to Synthetic Workhorse

The present review offers an overview of nonclassical (e.g., with no pre- or in situ activation of a carboxylic acid partner) approaches for the construction of amide bonds. The review aims to comprehensively discuss relevant work, which was mainly done in the field in the last 20 years. Organization of the data follows a subdivision according to substrate classes: catalytic direct formation of amides from carboxylic and amines (section 2); the use of carboxylic acid surrogates (section 3); and the use of amine surrogates (section 4). The ligation strategies (NCL, Staudinger, KAHA, KATs, etc.) that could involve both carboxylic acid and amine surrogates are treated separately in section 5.

Nonclassical Routes for Amide Bond Formation

An efficient method has been developed for direct amide bond synthesis between carboxylic acids and amines via (2-(thiophen-2-ylmethyl)phenyl)boronic acid as a highly active bench-stable catalyst. This catalyst was found to be very effective at room temperature for a large range of substrates with slightly higher temperatures required for challenging ones. This methodology can be applied to aliphatic, α-hydroxyl, aromatic, and heteroaromatic acids as well as primary, secondary, heterocyclic, and even functionalized amines. Notably, N-Boc-protected amino acids were successfully coupled in good yields with very little racemization. An example of catalytic dipeptide synthesis is reported.

Catalytic Chemical Amide Synthesis at Room Temperature: One More Step Toward Peptide Synthesis

(−)-Cytisine and Derivatives: Synthesis, Reactivity, and Applications

https://hal.archives-ouvertes.fr/hal-00871125/document

Brønsted acid catalyzed asymmetric aldol reaction: a complementary approach to enamine catalysis.

Asymmetric Malonic and Acetoacetic Acid Syntheses – A Century of Enantioselective Decarboxylative Protonations

https://hal-normandie-univ.archives-ouvertes.fr/hal-01793138/document

Jérôme Blanchet

Papers

Catalytic Chemical Amide Synthesis at Room Temperature: One More Step Toward Peptide Synthesis

(−)-Cytisine and Derivatives: Synthesis, Reactivity, and Applications

Brønsted acid catalyzed asymmetric aldol reaction: a complementary approach to enamine catalysis.

Asymmetric Malonic and Acetoacetic Acid Syntheses – A Century of Enantioselective Decarboxylative Protonations

Borinic acid catalysed peptide synthesis.