The reactions of 5-acyl-3-(1-pyridinio)thiophene-2-thiolates with dimethyl acetylenedicarboxylate in xylene at the reflux temperature afforded the corresponding 2-unsubstituted 5-acylthieno[3,2-d]thiazoles in 25-69% yields together with dimethyl phthalate as another fragmentation product. In a few reactions, the unexpected products, dimethyl 2-[2-acylthieno[2',3':2,3]-1,4-thiazino[4,5-a]pyrrol-8-ylidene]succinate derivatives, were also isolated, though their yields were very low.
A Through-Space Interaction of 3-Benzylthiothieno[3,4-b]indolizine Derivatives Combined by a Highly Flexible Spacer
Some ethyl 1 -benzoyl-3-[(un)substituted benzylthio]thieno[3,4-b]indolizine-9-carboxylates were prepared and their conformations were investigated. In the solid state and the chloroform solution they had stacked structures in which the phenyl ring and the pyridine moiety of theino[3,4-b]indolizine ring are partly overlapped.