CoH-catalyzed radical hydroalkylation of alkenes with 1,3-dicarbonyls

Abstract

Metal-hydride hydrogen atom transfer (MHAT) catalysis has emerged as a useful reaction platform for alkene hydrofunctionalization with high chemoselectivity and predictable branched selectivity. However, MHAT-mediated hydrofunctionalization involves carbon−carbon bond formation...

Transition-metal-catalyzed C–H bond alkylation using olefins: recent advances and mechanistic aspects

“…Very recently, the Zhang research group reported the intermolecular hydroalkylation of different alkenes 174b with various 1,3-dicarbonyls 174a to construct C(sp 3 )–C(sp 2 ) under Co-catalysis (Scheme 174). 273 Depending on the substrate, cobalt-complexes 174d or 174e were used in the presence of TMFP-BF 4 , TMDSO in toluene or THF solvent. The protocol showed wide functional group tolerance and could be operated under mild reaction conditions.…”

Intermolecular Hydroalkoxylation and Hydrocarboxylation of 2-Azadienes with High Efficiency

“…In aliphatic systems, the use of metal-catalyzed hydrogen atom transfer (MHAT, Scheme B) has enabled the hydrofunctionalization of alkenes with high regioselectivity . Further, use of cobalt-salen catalysts in the presence of an oxidant generates cation-like reactivity from the radical through radical-polar crossover (Scheme B). − This suggests that a cobalt-salen system for MHAT to 2-azadienes would be a feasible and novel route to 2-azaallyl cation equivalents. Here, we show that oxidative MHAT can be used to form hemiaminal ethers and esters via intermolecular hydroalkoxylation and hydrocarboxylation (Scheme ).…”

“…Oxidative MHAT hydrofunctionalizations have been demonstrated with a number of alkenes in a series of impactful papers. − Interestingly, these almost always use an excess of the nucleophilic trap. With the 2-azadiene reactions described here, on the other hand, it was possible to accomplish the coupling reaction using only 1.2 equiv of nucleophile.…”

Synthesis of Indeno[1,2-c]furans via Cobalt-Catalyzed Radical–Polar Crossover [3 + 2] Cycloaddition of o-Alkynylaryl β-Dicarbonyls

“…Herein, we report a mechanistically distinct, radical–polar crossover strategy , for the generation of indeno­[1,2- c ]­furans (Scheme C). This protocol features a catalytic system of a Co­(salen) complex and N -fluorobenzenesulfonimide (NFSI), − which readily undergoes single-electron transfer − to generate an amidyl radical as the competent hydrogen-atom transfer agent to react with β-dicarbonyl to afford the corresponding vinyl radical − and ultimately the anticipated polycyclic indeno­[1,2- c ]­furans via sequential intramolecular radical and polar cyclizations (see the related mechanistic experiments in Scheme S1). − …”