A Free-Radical Cascade Methylation/Cyclization of N-Arylacrylamides and Isocyanides with Dicumyl Peroxide

Abstract

A free-radical cascade methylation/cyclization of a wide range of N-arylacrylamides and isocyanides is demonstrated by using dicumyl peroxide as the methylating reagent, which provides a convenient and selective access to various methylated N-heterocycles such as oxindoles and phenanthridines.

Microwave‐Assisted Copper‐Catalyzed Oxidative Cyclization of Acrylamides with Non‐Activated Ketones

“…Based on these observations and literature reports, we propose a plausible catalytic cycle (Scheme ). The first step involves a copper‐assisted homolysis of DCP to generate a cumyloxyl radical . Thereafter, the selective hydrogen atom abstraction from acetophenone 2 a by the cumyloxyl radical generates the corresponding radical intermediate A , followed by its addition to the C=C bond of N ‐acrylamide 1 a , affording radical intermediate B .…”

Free‐Radical‐Promoted Alkenylation of C(sp3)−H Bond in Chloroalkane with Cinnamic Acid and β‐Nitrostyrene

“…An elevated temperature cound not give a better yield. Next an array of metal and or metal salts were screened (entries [7][8][9][10][11][12][13][14]. As a result, low yields of the products were obtained with or not the catalysts (entry 15).…”

Cobalt‐Catalyzed C(sp2)−H Methylation by using Dicumyl Peroxide as both the Methylating Reagent and Hydrogen Acceptor

“…[10][11][12] However,d irectC ÀH methylations by using cobalt catalysis have been very rare and have been achieved only on two isolated substrates, N-methyl-1-naphthamide [9f] and benzo[h]quinoline [9g] with MeMgBra s the methyl source under oxidative conditions. In this paper,we would like to report the cobalt(II)-catalyzed direct CÀHm ethyl-ation of unactivated (hetero)arenes by using dicumyl peroxide (DCP) [13] as both the methyl source and hydrogen acceptor, and 2-pyridinyl isopropyl (PIP) [14] as ab identate directing auxiliary (Scheme 1B).…”

“…[Co(acac) 3 ]p roduced the desired product in moderate yield (entry 10), suggesting that the reaction may be initiated by acobalt(III) species. Severalother peroxides were investigated in this reaction (entries [11][12][13], and it was found that dicumyl peroxide (DCP) provided the best result with an 88 % yield of 2a.T he product 2a was formed in 80 %y ield when 5mol %[ Co(acac) 2 ]w as used in this reaction (entry 14), andn o product waso bserved in the absence of ac obalt catalyst (entry 15).…”

“…[9e] Alternatively, alkoxy radical oxidative addition into the cobalt center, and subsequent b-methyl elimination generates acetophenone and cobalt complex C. [13] Finally,t he catalytic cycle is completed by reductivee limination of the cobalt complex C,f ollowed by protonation giving the product 2a and aC o II species. In summary, an efficient cobalt(II)-catalyzedd irect methylation of unactivated C(sp 2 )ÀHb onds through aC ÀHb ond activation process has been developed.T his transformation represents the first example of cobalt-catalyzed direct methylation of aC (sp 2 )ÀHb ond using dicumyl peroxide (DCP) as both the methylating reagenta nd hydrogen acceptor.T he reactionp roceeds with aw ide variety of substrates and high functionalgroup tolerance, which allows effective access to aw ide range of o-methylated (hetero)aromatic carboxamides.…”