Electro-oxidative Intermolecular Allylic C(sp3)-H Aminations

An Electrochemical Oxo-amination of 2H-Indazoles: Synthesis of Symmetrical and Unsymmetrical Indazolylindazolones

We have established a supporting-electrolyte free electrochemical method for the synthesis of indazolylindazolones through oxygen reduction reaction (eORR) induced 1,3-oxo-amination of 2H-indazoles where 2H-indazole is used as both aminating agent as well as the precursor of indazolone. Moreover, we have merged indazolone and indazole to get unsymmetrical indazolylindazolones through direct electrochemical cross-dehydrogenative coupling (CDC). This exogenous metal-, oxidant- and catalyst-free protocol delivered a number of multi-functionalized products with high tolerance of diverse functional groups.

Electrochemical decarboxylative alkylation of β-ketoacids with phenol derivatives

An electrochemical method for the decarboxylative alkylation of β-ketoacids with phenol derivatives has been developed. The protocol was carried out in readily available unseparated cells at room temperature in the absence of catalysts and oxidants. The corresponding aryl ketones were obtained in satisfactory yields without additional electrolytes, and were easy to produce in gram-scale synthesis. Based on control experiments and cyclic voltammetry, a plausible reaction mechanism was proposed.

Nickel-Catalyzed Chemo- and Enantioselective Hydrogenation and Deuteration of α,β-Unsaturated Ketimines Using Alcohols: Synthesis of Deuterated Chiral Allylic Amines

A nickel-catalyzed chemoselective asymmetric transfer hydrogenation of α,β-unsaturated ketimines using ethanol as a hydrogen donor under mild conditions that avoid using high-pressure hydrogen gas was developed. With this catalyst, C1-selective deuterated chiral allylic amines were efficiently synthesized using only stoichiometric 2-propanol-d8. Mechanism studies demonstrated the formation of a nickel hydride intermediate.

Electrochemical Late-Stage Functionalization

Late-stage functionalization (LSF) constitutes a powerful strategy for the assembly or diversification of novel molecular entities with improved physicochemical or biological activities. LSF can thus greatly accelerate the development of medicinally relevant compounds, crop protecting agents, and functional materials. Electrochemical molecular synthesis has emerged as an environmentally friendly platform for the transformation of organic compounds. Over the past decade, electrochemical late-stage functionalization (eLSF) has gained major momentum, which is summarized herein up to February 2023.

Metalloradical approach for concurrent control in intermolecular radical allylic C-H amination

Although they offer great potentials, the high reactivity and diverse pathways of radical chemistry pose difficult problems for applications in organic synthesis. In addition to the differentiation of multiple competing pathways, the control of various selectivities in radical reactions presents both formidable challenges and great opportunities. To regulate chemoselectivity and regioselectivity, as well as diastereoselectivity and enantioselectivity, calls for the formulation of conceptually new approaches and fundamentally different governing principles. Here we show that Co(II)-based metalloradical catalysis enables the radical chemoselective intermolecular amination of allylic C-H bonds through the employment of modularly designed D2-symmetric chiral amidoporphyrins with a tunable pocket-like environment as the supporting ligand. The reaction exhibits a remarkable convergence of regioselectivity, diastereoselectivity and enantioselectivity in a single catalytic operation. In addition to demonstrating the unique opportunities of metalloradical catalysis in controlling homolytic radical reactions, the Co(II)-catalysed convergent C-H amination offers a route to synthesize valuable chiral α-tertiary amines directly from an isomeric mixture of alkenes.

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

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.

Divergent C-H Amidations and Imidations by Tuning Electrochemical Reaction Potentials

Electrochemical C-H functionalizations are attractive transformations, as they are capable of avoiding the use of transition metals, pre-oxidized precursors, or suprastoichiometric amounts of terminal oxidants. Herein an electrochemically tunable method was developed that enabled the divergent formation of cyclic amines or imines by applying different reaction potentials. Detailed cyclic voltammetry analyses, coupled with chronopotentiometry experiments, were carried out to provide insight into the mechanism, while atom economy was assessed through a paired electrolysis. Selective C-H amidations and imidations were achieved to afford five- to seven-membered sulfonamide motifs that could be employed for late-stage modifications.

Iron–iodine co-catalysis towards tandem C–N/C–C bond formation: one-pot regioselective synthesis of 2-amino-3-alkylindoles

An efficient intermolecular C2,3-H aminoalkylation of indoles with 9H-xanthenes and azoles via iron–iodine co-catalyzed tandem C–N/C–C bond formation has been developed.

Electricity-driven redox-neutral C(sp3)–H amidation with N-alkoxyamide as an amidating reagent

An electrochemical redox-neutral C(sp3)–H amidation was developed with N-alkoxyamide as an amidating reagent. Under sequential paired electrolysis, N-alkoxyamides showed higher reactivity compared to the direct reaction of primary amides.

Electrochemical oxidative synthesis of 2-benzoylquinazolin-4(3H)-one via C(sp3)–H amination under metal-free conditions

An electrochemically induced C(sp3)–H amination of 2-aminobenzamides with ketones using TBAI as a catalyst was developed, and provided 2-benzoylquinazolin-4(3H)-ones under metal-free conditions.