Thiophene 2.5- diacetic acid

In terms of actual chemistry, the first example of this class of macrocycles to be prepared was, as mentioned above, the [ISjannulene-trisulfide derivative 2.335. " This macrocycle was obtained by reacting thiophene-2,5-diacetic acid 2.346 with... 

High-yielding Suzuki substitutions of halogen in halo-boronates are also possible using Al-methylimino-diacetic acid (MIDA) to form the protected boronate, which resists coupling under anhydrous conditions. This approach has been applied to aryl and heteroaryl (only thiophene and benzofuran, shown below) systems, and also for polyene synthesis. ... 

The reactivity of selenophen has been compared with that of thiophen and the relative reactivities in five different electrophilic substitutions have been determined by kinetic or competitive procedures. Selenophen was found to be 1.5—47.5 times more reactive than thiophen. Selenophen has been chloromethylated to 2,5-dichloromethylselenophen, which has been used for the syntheses of other 2,5-substituted derivatives such as the diacetic acid. ... 

Some other derivatives of thiophene were studied and described, e.g. 2-thenylmercaptane (10) and 5-nitro 2-thiophene aldehyde were synthesized by means of a selenium dioxide oxidation of 5-nitro-2-thenylbromide (23). On the other hand the same aldehyde could be obtained by nitration of 2-thenaldehydediacetate (66). This diacetate was cleaved (76% yield) by steam distillation from dilute hydrochloric acid. 

Thiophenes are oxidised in methanol containing sulphuric acid, using an undivided cell, to give- acetals with loss of the sulphur as sulphur dioxide. Thiophene itself affords the diacetal 60 [195] and related reactions are found for 2-, 3- and 2,5-substituted thiophenes [196, 197], Reaction of 2-hydroxymethylthiophcne does... 

Secondary aliphatic amines reacted readily with mercaptoaldimines (279), which could be prepared readily by the action of Na/NH3 on the aldehyde diacetals (278). The resulting N,N- dialkyl derivatives (280) were alkylated on sulfur by a-halocarbonyl compounds such as bromoacetic acid the resulting products (281) underwent spontaneous ring closure and aromatization via loss of the secondary amine to yield the acids (282 Scheme 97). Decarboxylation of the acids (282) furnished the substituted thieno[2,3-6 ]thiophenes (283). The use of other a-halocarbonyl compounds, such as bromoacetone or phenacyl bromide for the alkylation, led to the formation of the 2-acetyl or 2-benzoyl derivatives, (284) and (285) respectively (76AHC(19)123). 

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