Cobalt-Catalyzed Markovnikov-Selective Radical Hydroacylation of Unactivated Alkenes with Acylphosphonates

Abstract

Acylphosphonates having the 5,5-dimethyl-1,3,2-dioxophosphinanyl skeleton are developed as efficient intermolecular radical acylation reagents, which enable the cobalt-catalyzed Markovnikov hydroacylation of unactivated alkenes at room temperature under mild conditions. The protocol exhibits broad substrate scope and wide functional group compatibility, providing branched ketones in satisfactory yields. A mechanism involving the Co–H mediated hydrogen atom transfer and subsequent trapping of alkyl radicals by acylphosphonates is proposed.

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

“…In this context, the intra-or inter-molecular hydroacylations majorly rely on reactant-based chelation assistance 210 and radical mediated hydroacylation. However, the radical mediated hydroacylation [213][214][215][216][217] is out of the scope of this review. The discussion is divided based on the type of metal catalyst involved in the process (Scheme 130).…”

Recent Advances in Cobalt‐catalyzed Functionalization of Unactivated Olefins

“…The initial reaction was performed using 4‐phenylbut‐1‐ene as the model substrate and the optimized condition was realized with cobalt‐salen complex ( 87 ) as the catalyst along with PhSiH 3 as a hydrogen source, TBHP as a oxidant, 1‐chloromethyl‐4‐fluorodiazoniabicyclo [2.2.2] octane bis(tetrafluoroborate) (selectfluor) as an additive at room temperature for 12 h (Scheme 41). [40] Under the optimum conditions, various functional groups such as electron‐donating and electron‐withdrawing groups containing terminal alkenes underwent hydroacylation reaction smoothly to afford the corresponding products in satisfactory yields along with exclusive Markovnikov selectivity. This reaction was also amenable to internal alkenes.…”

“…[22] This methodology exhibits mild reaction conditions, broad substrate scope, large functional groups tolerance and excellent regio-and stereoselectivity. The cobaltcatalyzed reaction between benzoic acid derivatives (40) and trans 4-octene ( 41) took place optimally in the presence of 20 mol % Co(OAc) 2…”

“…Recently various functionalization of unactivated olefins has been reported such as alkylation, hydropyridylation, hydroarylation, hydroamination, difluoroalkylation-peroxidation, rifluoromethylation-peroxidation, hydroboration, hydrotrifluoroethylation, aminofluorination and hydroacylation. [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] Herein, we majorly focussed on the cobalt-catalyzed functionalization of unactivated olefins.…”

α-Branched amines through radical coupling with 2-azaallyl anions, redox active esters and alkenes

“…In recent years, the emergence of redox active esters (RAEs) as alkyl radical precursors has marked a milestone in the art of organic synthesis (Scheme 3a), [49][50][51][52][53][54][55][56][57][58][59][60] particularly when combined with transition metal-catalyzed processes, such as alkene difunctionalization (Scheme 3b). [61][62][63][64][65][66][67][68][69][70][71][72][73] In light of these advances, and our previous work on 2-azaallyl radical chemistry, we envisioned that even weakly reducing 2-azaallyl anions could match the redox properties of RAE to initiate the SET reduction and generate alkyl radicals and 2-azaallyl radicals. It was initially envisioned that the transient alkyl radical could be trapped by suitably activated alkenes in the presence of transition metal catalysts.…”