Pyrazole-, Thiazole-, and Imidazole-fused Thiophens

Pyrazole-, Thiazole , and Imidazole fused Thiophens.—Starting from (410) and carrying out nucleophilic substitution with thioglycolate followed by ring-closure, as described for (384) and (408), the thieno[2,3-d]pyrazole system (411) was synthesized. Their ionization constants have been determined and the transmission of the influence of the substituents R has been studied and found to be more feeble than in naphthalene d benzo[b]thiophen. From the cyano-derivative (412), thiophen-fused derivatives such as (413) and (414) have been synthesized. Electrophilic 

From (416) the thieno[2,3-4]thiazolidine system (417) was prepared by the same method as that used for (411). 2-Aminothiophen hydrochlorides 

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Pyrazole-, Thiazole-, and Imidazole-fused Thiophens and Related Systems.— The behaviour of thieno- and selenolo-t-3,2-i/]pyrazoles in formylation and bromina-tion reactions has been studied. In contrast to benzo[fe]thiophen, a substituent is directed into the a-position of the condensed thiophen ring. 2-Mercapto-thieno[3,2-prepared from 2-chloro-3-nitrothiophen and sodium disulphide followed by carbon disulphide. A benzo-fused system was prepared similarly from 3-bromo-2-nitrobenzo[6]thiophen. Derivatives of... 

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