Synthesis and X-ray characterisation of a new polycondensed heterocycle obtained by a novel Mn(III)-mediated cascade reaction of 2-cyanophenyl isothiocyanate
2-Cyanophenyl isothiocyanate reacted with Mn(III) acetate in acetic acid or acetonitrile to give fair yields of a new polycondensed heterocycle arising from the joining together of two molecules of the starting isothiocyanate with loss of a CS moiety. The yields were close to 90% when the reaction was carried out in the presence of diethyl malonate. This compound was unambiguously identified by X-ray crystallography. Under the same conditions, 2-(methoxycarbonyl)phenyl isothiocyanate gave a quinazolinimine derivative instead which is likely to arise from cyclisation of an intermediate N,N′-diarylthiourea. The mechanism of formation of the former compound probably involves formation of a N,N′-bis(2-cyanophenyl)thiourea, followed by rearrangement and radical tandem ring closure of the corresponding cyclic imine derivative. This hypothesis is also supported by semiempirical calculations.
Calestani, Gianluca,Capella, Laura,Leardini, Rino,Minozzi, Matteo,Nanni, Daniele,Papa, Romina,Zanardi, Giuseppe
p. 7221 - 7233
(2007/10/03)
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