C. Chan, J. C. Ma, T. Mak
1977
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0
Influential Citations
4
Citations
Journal
Journal of The Chemical Society-perkin Transactions 1
Abstract
The product from 2-aminobenzothiazole and dimethyl but-2-ynedioate has been shown by X-ray analysis to be the title compound (IIIa). Crystals of (IIIa) are monoclinic, space group P21/c, with a= 4.801(5), b= 13.68(1), c= 20.37(2)A, β= 90.44(5)°, and Z= 4. The structure was solved by direct methods and refined by full-matrix least-squares to R 0.099 for 1 931 observed photographic intensities.The molecule consists of an exocyclic carbonyl group and a methyl ester group linked to a slightly warped C6–C3NS–C4N2 ring skeleton. The carboxy-group makes a dihedral angle of 34° with the mean plane of the heterocyclic ring system. The sulphur atom participates in the molecular π-bonding, and bond-length variations in the tricyclic ring system are well accounted for in terms of simple Huckel MO theory.A reaction mechanism is suggested which involves an initial Michael addition on an acetylenic carbon by the ring nitrogen, forming an enamine with the fumarate structure. Subsequent ring-closure involving the β-methoxycarbonyl- and imino-groups leads to the formation of the product.