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REACTIONS OF QUINOLINECARBALDEHYDES WITH ARENES UNDER SUPERELECTROPHILIC ACTIVATION. NMR AND DFT STUDIES OF DICATIONIC ELECTROPHILIC SPECIES

Marina А. Borisova, Dmitry S. Ryabukhin, Alexander Yu. Ivanov, Irina A. Boyarskaya, Dar’ya V. Spiridonova, Mikhail O. Kompanets, Aleksander V. Vasilyev
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Abstract


N,O-Diprotonated forms (dications) of various quinolinecarbaldehydes were theoretically studied by DFT calculations. It was found that the most reactive electrophilic dications are expected to be generated from 2- and 4-quinolinecarbaldehydes compared to the other quinolinecarbaldehydes. Experimental studies of protonation of quinoline-2(6,8)-carbaldehydes in Brønsted acids (CF3SO3H, H2SO4) by means of 1H, 13C, and 15N NMR revealed the formation of the corresponding N-protonated O-protosolvated species. Reactions of quinoline-2(6,8)-carbaldehydes with arenes in the presence of Brønsted (TfOH) and Lewis acids (AlX3, X = Cl, Br) or acidic zeolites led to the formation of the corresponding 2(6,8)-(diarylmethyl)quinolines. However, 6- and 8-quinolinecarbaldehydes gave additionally unusual products – 6(8)-(arylmethyl)quinolines.


Keywords


quinolines; carbocations; DFT calculations; Friedel–Crafts reaction; superelectrophilic activation.

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