Transition-Metal-Free Alkylation and Acylation of Benzoxazinones with 1,4-Dihydropyridines

The direct functionalization of N-heterocycles is a vital transformation for the development of pharmaceuticals, functional materials, and other chemical entities. Herein, the transition-metal-free alkylation and acylation of C(sp²)-H bonds in biologically relevant 2-benzoxazinones with 1,4-dihydropyridines as readily accessible radical surrogates is described. Excellent functional group compatibility and a broad substrate scope were attained. Gram-scale reaction and transformations of the synthesized adducts via Suzuki coupling with heteroaryl boronic acids demonstrated the synthetic potential of the developed protocol.

Chemoselective Cu-catalyzed synthesis of diverse N-arylindole carboxamides, β-oxo amides and N-arylindole-3-carbonitriles using diaryliodonium salts

Chemoselective copper-catalyzed synthesis of diverse N-arylindole-3-carboxamides, β-oxo amides and N-arylindole-3-carbonitriles from readily accessible indole-3-carbonitriles, α-cyano ketones and diaryliodonium salts has been developed. Diverse N-arylindole-3-carboxamides and β-oxo amides were successfully achieved in high yields under copper-catalyzed neutral reaction conditions, and the addition of an organic base (DIPEA) resulted in a completely different selectivity pattern to produce N-arylindole-3-carbonitriles. Moreover, the importance of the developed methodology was realized by the synthesis of indoloquinolones and N-((1H-indol-3-yl)methyl)aniline and by a single-step gram-scale synthesis of the naturally occurring cephalandole A analogue.

Recent Advances on Copper-Catalyzed C–C Bond Formation via C–H Functionalization

Reactions that form C–C bonds are at the heart of many important transformations, both in industry and in academia. From the myriad of catalytic approaches to achieve such transformations, those relying on C–H functionalization are gaining increasing interest due to their inherent sustainable nature. In this short review, we showcase the most recent advances in the field of C–C bond formation via C–H functionalization, but focusing only on those methodologies relying on copper catalysts. This coinage metal has gained increased popularity in recent years, not only because it is cheaper and more abundant than precious metals, but also thanks to its rich and versatile chemistry.

1 Introduction

2 Cross-Dehydrogenative Coupling under Thermal Conditions

2.1 C(sp3)–C(sp3) Bond Formation

2.2 C(sp3)–C(sp2) Bond Formation

2.3 C(sp2)–C(sp2) Bond Formation

2.4 C(sp3)–C(sp) Bond Formation

3 Cross-Dehydrogenative Coupling under Photochemical Conditions

3.1 C(sp3)–C(sp3) Bond Formation

3.2 C(sp3)–C(sp2) and C(sp3)–C(sp) Bond Formation

4 Conclusion and Perspective

3d Transition Metals for C-H Activation

C-H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material sciences, crop protection, drug discovery, and pharmaceutical industries, among others. Despite major advances, the vast majority of these C-H functionalizations required precious 4d or 5d transition metal catalysts. Given the cost-effective and sustainable nature of earth-abundant first row transition metals, the development of less toxic, inexpensive 3d metal catalysts for C-H activation has gained considerable recent momentum as a significantly more environmentally-benign and economically-attractive alternative. Herein, we provide a comprehensive overview on first row transition metal catalysts for C-H activation until summer 2018.

Visible-light-induced C(sp3)-H activation for a C-C bond forming reaction of 3,4-dihydroquinoxalin-2(1H)-one with nucleophiles using oxygen with a photoredox catalyst or under catalyst-free conditions

A convenient photocatalyzed oxidative coupling reaction of 4-alkyl-3,4-dihydroquinoxalin-2(1H)-one and its derivatives with a variety of nucleophiles was developed with a ruthenium photoredox catalyst and oxygen under a household compact fluorescent light. With a slower reaction rate, the cross coupling transformation can be achieved in the absence of an external photocatalyst with a similar isolated yield. An application to the synthesis of natural product cephalandole A was also demonstrated.