American Chemical Society
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Reactions of Tetracyanoethylene with N′‑Arylbenzamidines: A Route to 2‑Phenyl‑3H‑imidazo[4,5‑b]quinoline-9-carbonitriles

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journal contribution
posted on 2016-02-18, 22:49 authored by Styliana I. Mirallai, Maria Manoli, Panayiotis A. Koutentis
Eight 2-phenyl-3H-imidazo­[4,5-b]­quinoline-9-carbonitriles 15 are prepared in four steps from N′-arylbenzamidines 11 and tetracyanoethylene (TCNE) in ∼70–90% yields. The transformation involves the initial formation of N-aryl-N′-(1,2,2-tricyanovinyl)­benzamidines 12 in 87–99% yields, which in MeCN undergo a 5-exodig cyclization to give the 2-[1-aryl-5-imino-2-phenyl-1H-imidazol-4­(5H)-ylidene]­malononitriles 13 in 84–92% yields, while in MeOH the (Z)-2-[2-phenyl-4-(arylimino)-1H-imidazol-5­(4H)-ylidene]­malononitriles 14 are formed in 85–94% yields. The imidazoles 14 can also be prepared directly from imidazoles 13 via a Dimroth rearrangement in either neat MeOH or in DCM with DBU. Subsequent thermolysis of imidazoles 14 in diphenyl ether affords 2-phenyl-3H-imidazo­[4,5-b]­quinoline-9-carbonitriles 15 in near quantitative yields. Mechanistic rationale is provided for all transformations.