C–H and N–H Bond Annulation of Benzamides with Isonitriles Catalyzed by Cobalt(III)

Abstract

A simple efficient, atom-economical procedure was developed for the cobalt-catalyzed C-H bond annulation of benzamides with isonitriles under mild conditions. The reaction tolerates a variety of functional group including heterocycles. Diverse 3-(alkylimino)-2-quinolin-8-yl-2,3-dihydro-1H-isoindol-1-ones were synthesized using isonitriles as the C1 source through C-H and N-H bond annulation via C-H bond activation in a 'green' solvent. Vinylamides were also used similarly with tert-butyl isonitrile to give 3-(tert-butylimino)-1-quinolin-8-yl-1H-pyrrol-2(5H)-ones.

A comprehensive overview of directing groups applied in metal-catalysed C–H functionalisation chemistry

“…In 2016 and 2017, three protocols using a Co catalyst were studied by the groups of Hao, 435 Ji 437 and Sundararaju. 436 In the former case ( Scheme 70C ), synthetically useful yields were obtained (30–85%) and a mixture of regioisomers was only observed for the arenecarboxamide bearing a fluorine as substituent at the meta position.…”

“…The protocol reported by Sundararaju provided the same selectivity ( Scheme 70D ), good yields (35–96% yield), and a mixture of regioisomers was only observed with meta -trifluoromethylated arenecarboxamides. 436 An extension to acrylamide derivatives was possible, albeit the corresponding products were obtained only with poor to moderate yields (27–63%).…”

CoIII‐Catalyzed Isonitrile Insertion/Acyl Group Migration Between C−H and N−H bonds of Arylamides

“…For example, 1,3‐acyl migrated product 3 a was obtained with or without the addition of silver carbonate using TFE as solvent (Scheme a (i),(ii)). On the other hand, the traditional insertion product 3 a’ was obtained starting from intermediate A , when CPME was used as the solvent (Scheme a (iii)) . This indicates that new insertion pathway was operated using TFE as solvent.…”

“…Ligand exchange followed by insertion into Co−C leads to intermediate H . This undergoes further classical reductive elimination to give 3 a’ under our standard conditions if a polar aprotic solvent (CPME) is used . However, if a polar protic solvent such as 2,2,2‐trifluoroethanol is used in this reaction, this will co‐ordinate to high‐valent, penta‐coordinated 16 e − intermediate H followed by reductive addition, leading to Co II intermediate I .…”

Isoindolinone Synthesis via One‐Pot Type Transition Metal Catalyzed C−C Bond Forming Reactions

“…Av ariety of cobalt catalyzed methodologies for synthesis of 3iminoisosindolinones have been published during the past ten years,w ith ac ommonf eature in the use of 8-quinolinyl (Q) directingg roup. Gu et al [84] described the use of oxidative CÀH functionalization/annulation cascade with cobalt(II) acetate as the catalyst and tert-butyl peroxybenzoate as the oxidant (Scheme 36 A), followed by Hao [85] and Sundararaju [86] using cobalt(II) acetyl acetonate and silver salt as the oxidant (Scheme 36 Ba nd C, respectively). Later,S undararaju [87] reported ag eneral site-selective cobalt-catalyzed insertion of isocya-nides to form aryl amides through CÀHb onda ctivation and alcohol assisted intramolecular trans-amidation with as ignificantly broad substrate scope( Scheme 36 D).…”