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

Transition-metal-catalyzed cross-coupling reactions have been well-established as indispensable tools in modern organic synthesis. One of the major research goals in cross-coupling area is expanding the scope of the coupling partners. In the past decade, diazo compounds (or their precursors N-tosylhydrazones) have emerged as nucleophilic cross-coupling partners in C–C single bond or C═C double bond formations in transition-metal-catalyzed reactions. This type of coupling reaction involves the following general steps. First, the organometallic species is generated by various processes, including oxidative addition, transmetalation, cyclization, C–C bond cleavage, and C–H bond activation. Subsequently, the organometallic species reacts with the diazo substrate to generate metal carbene intermediate, which undergoes rapid migratory insertion to form a C–C bond. The new organometallic species generated from migratory insertion may undergo various transformations. This type of carbene-based coupling has proven...

Transition-Metal-Catalyzed Cross-Couplings through Carbene Migratory Insertion

Recently, the use of enantiomerically pure counteranions for the induction of asymmetry in reactions proceeding through cationic intermediates has emerged as an exciting new concept, which has been termed asymmetric counteranion-directed catalysis (ACDC). Despite its success, the concept has not been fully defined and systematically discussed to date. This Review closes this gap by providing a clear definition of ACDC and by examining both clear cases as well as more ambiguous examples to illustrate the differences and overlaps with other catalysis concepts.

Asymmetric Counteranion-Directed Catalysis: Concept, Definition, and Applications

The development of new methods for the direct functionalization of unactivated C–H bonds is ushering in a paradigm shift in the field of retrosynthetic analysis. In particular, the catalytic enantioselective functionalization of C–H bonds represents a highly atom- and step-economic approach toward the generation of structural complexity. However, as a result of their ubiquity and low reactivity, controlling both the chemo- and stereoselectivity of such processes constitutes a significant challenge. Herein we comprehensively review all asymmetric transition-metal-catalyzed methodologies that are believed to proceed via an inner-sphere-type mechanism, with an emphasis on the nature of stereochemistry generation. Our analysis serves to document the considerable and rapid progress within in the field, while also highlighting limitations of current methods.

/pdf/catalytic-enantioselective-transformations-involving-c-h-4dm3wav9qj.pdf

Catalytic Enantioselective Transformations Involving C-H Bond Cleavage by Transition-Metal Complexes.

The combination of transition metal catalysis and organocatalysis as a new and exciting research area has attracted increasing attention as it can enable the development of unprecedented transformations that is not possible by use of either of the catalytic systems alone, and can improve the reactivity, efficiency and stereocontrol of existing chemical transformations. In this review, we summarize recent remarkable progress in the field of combined transition metal catalysis and organocatalysis, further highlighting the potential of this new and exciting research area and the many challenges that still remain for the future.

Combining transition metal catalysis and organocatalysis--an update.

Palladium-Catalyzed Allylic Alkylation via Photocatalytic Nucleophile Generation

A chiral phosphoramidite ligand-controlled palladium-catalyzed asymmetric intramolecular allylic C-H amination has been established to prepare various substituted chiral tetrahy-dropyrimidines in high levels of yields and enantioselectivities. Particularly, dienyl sodium N-sulfonyl amides bearing an ar-ylethene-1-sulfonyl group underwent sequential allylic C-H amination and intramolecular Diels-Alder (IMDA) reaction to produce chiral fused tricyclic tetrahydropyrimidine frameworks in high yields and stereoselectivities. Significantly, an asym-metric synthesis of letermovir has been accomplished by using this method as the key step.

An Unprecedented Access to Chiral Tetrahydropyrimidines via Palladium-Catalyzed Asymmetric Allylic C-H Amination

Access to chiral γ-butenolides via palladium-catalyzed asymmetric allylic C–H alkylation of 1,4-dienes

Allylamines are important building blocks in the synthesis of bioactive compounds. The direct coupling of allylic C-H bonds and commonly available amines is a major synthetic challenge. An allylic C-H amination of 1,4-dienes has been accomplished by palladium catalysis. With aromatic amines, branch-selective allylic aminations are favored to generate thermodynamically unstable Z-allylamines. In addition, more basic aliphatic cyclic amines can also engage in the reaction, but linear dienyl allylic amines are the major products.

Palladium-Catalyzed Branch- and Z-Selective Allylic C-H Amination with Aromatic Amines.

Enantioselective functionalization of alkenes is an attractive and straightforward method to assemble molecular complexity from readily available chemical feedstocks. Although regio- and enantioselective transformations of the C=C bond of alkenes have been extensively studied, those of the allylic C–H bonds of unactivated alkenes are yet to be explored. Here we report a palladium-catalysed branch- and enantioselective allylic C–H alkylation that is capable of accommodating diverse types of α-alkenes, ranging from feedstocks annually manufactured on a million-tonne scale to olefins tethering a wide scope of appended functionalities, providing unconventional access to chiral γ,δ-unsaturated amides. Notably, mechanistic studies reveal that regioselectivity is not only governed by the coordination pattern of nucleophiles but also regulated by the ligational behaviours of ligands, highlighting the importance of the monoligation of chiral phosphoramidite ligands in provoking high levels of stereo- and branch-selectivity via a nucleophile coordination-enabled inner-sphere allylation pathway. The selective functionalization of C=C bonds of alkenes is well studied, however, regio- and enantioselective transformations of the allylic C–H bond of unactivated alkenes are relatively underexplored. Now, a palladium-catalysed branch-selective and enantioselective allylic C−H alkylation of α-alkenes is reported. The process tolerates a wide range of α-alkenes, from chemical feedstocks to bioactive α-alkenes 

/pdf/palladium-catalysed-branch-and-enantioselective-allylic-c-h-1macryr0.pdf

Pu-Sheng Wang

Papers

Palladium-Catalyzed Allylic Alkylation via Photocatalytic Nucleophile Generation

An Unprecedented Access to Chiral Tetrahydropyrimidines via Palladium-Catalyzed Asymmetric Allylic C-H Amination

Access to chiral γ-butenolides via palladium-catalyzed asymmetric allylic C–H alkylation of 1,4-dienes

Palladium-Catalyzed Branch- and Z-Selective Allylic C-H Amination with Aromatic Amines.

Palladium-catalysed branch- and enantioselective allylic C–H alkylation of α-alkenes