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Modulating the Reactivity of Functionalized N,S-Ketene Acetal in MCR: Selective Synthesis of Tetrahydropyridines and Thiochromeno[2,3-b]pyridines via DABCO-Catalyzed Tandem Annulation

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posted on 04.05.2012, 00:00 by Li-Rong Wen, Yong-Jie Shi, Guang-Yuan Liu, Ming Li
An efficient and straightforward three-component synthetic protocol was developed to synthesize 1,2,3,4-tetrahydropyridine derivatives or thiochromeno­[2,3-b]­pyridine derivatives from β-aroylthioacetanilides or β-(2-haloaroyl)­thioacetanilides, aldehydes, and aroyl acetonitriles via DABCO-catalyzed tandem [3 + 2 + 1] annulation and SNAr reaction. This synthetic approach has the prominent features of high chemo-, stereo- (or enantio-), and unusual regioselectivity. In the domino processes, at least seven reactive sites were involved, and up to three covalent bonds and one functionalized pyridine ring were generated. This facile and efficient reaction is a quite general for the preparation of tetrahydropyridine derivatives or thiochromeno­[2,3-b]­pyridine derivatives.