β Scribed by Alexander McKillop; Geoffrey C.A. Bellinger; Peter N. Preston; Alex Davidson; Trevor J. King
No coin nor oath required. For personal study only.
Reaction of benzimidazole-2(2@-thione 2 with dimethyl acetylenedicarboxylate (DMAD) has been reported by Grinblat and Postovskii to give the thiazolo[3,2-albenzimidazole 2.' On mechanistic grounds, however, condensation of i with DMAD can give rise to one or more of at least four products ,2, 2, 4~ and ,5, depending on whether (a> nitrogen or sulphur participates in the initial conjugate addition reaction, and (b) ring closure results in the formation of a 5-or g-membered ring. As there is no clear mechanistic basis 4, 2 R = COOCH3
;R=H
π SIMILAR VOLUMES
AbstractΓReaction of 2-unsubstituted 1H-imidazole 3-oxides with isocyanates, isothiocyanates, and dimethyl acetylenedicarboxylate led to the formation of 2-functionalized imidazole derivatives. Stepwise reaction mechanisms via zwitterionic intermediates are proposed. The intermediate [312] cycloaddu