Manganese-catalyzed cascade annulations of alkyne-tethered N-alkoxyamides: synthesis of polycyclic isoquinolin-1(2H)-ones

Rh(III)-Catalyzed Regioselective Alkyne Insertion in the Context of C-H Activation and Lactonization Reactions: Synthesis of Fused 1,2-Oxaphospholenes

Herein, we report an expedient synthesis of fused phosphorus-containing heterocycles via Rh-catalyzed cascade C-H activation, alkyne insertion, and lactonization reactions. The substrate scope and the group tolerance are good, as various substituted benzoic acids, N-methoxybenzamides, and 2-phenylindoles could go through the reactions smoothly to afford the corresponding products in moderate to high yields. Additionally, excellent regioselectivities are shown in the alkyne insertion with the assistance of an electron-withdrawing phosphonate group.

Strategies and Mechanisms of First-Row Transition Metal-Regulated Radical C-H Functionalization

Radical C-H functionalization represents a useful means of streamlining synthetic routes by avoiding substrate preactivation and allowing access to target molecules in fewer steps. The first-row transition metals (Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) are Earth-abundant and can be employed to regulate radical C-H functionalization. The use of such metals is desirable because of the diverse interaction modes between first-row transition metal complexes and radical species including radical addition to the metal center, radical addition to the ligand of metal complexes, radical substitution of the metal complexes, single-electron transfer between radicals and metal complexes, hydrogen atom transfer between radicals and metal complexes, and noncovalent interaction between the radicals and metal complexes. Such interactions could improve the reactivity, diversity, and selectivity of radical transformations to allow for more challenging radical C-H functionalization reactions. This review examines the achievements in this promising area over the past decade, with a focus on the state-of-the-art while also discussing existing limitations and the enormous potential of high-value radical C-H functionalization regulated by these metals. The aim is to provide the reader with a detailed account of the strategies and mechanisms associated with such functionalization.

Late-stage ortho-C-H alkenylation of 2-arylindazoles in aqueous medium by Manganese(i)-catalysis

Earth-abundant and water-tolerant manganese(i) catalyzed alkenylation of 2-arylindazole with alkyl and aryl alkynes through C–H bond activation is described with a unique level of E-selectivity. The reaction proceeds through the control of C3 nucleophilicity of 2-aryl indazoles. This method is applied to the late-stage functionalization of complex molecules including ethinylestradiol, norethisterone, and N-protected amino acid derivatives. The kinetic isotope studies suggest that the C–H bond activation step may not be the rate-determining step.

Earth-abundant and water-tolerant manganese(i) catalyzed alkenylation of 2-arylindazole with alkyl and aryl alkynes through C–H bond activation is described with a unique level of E-selectivity.