3- Bromothiophene Grignard reagent from

The usefulness of the Grignard reagent of 3-bromothiophene is somewhat limited as it can only be prepared by the entrainment method. The simultaneous formation of Grignard reagents from 3-bromothiophene and a fivefold molar excess of ethyl bromide gave, however, a 55% yield of 3-thiophenecarboxylic acid upon carbona-tion. With acetaldehyde, a 55% yield of methyl 3-thienyl carbinol... 

As already mentioned, unsubstituted polythiophene is an insoluble and infusible material. Once the polymer is prepared, it is difficult (if not impossible) to process it further as a material for electronic applications. The solubility can be greatly enhanced by the introduction of side-chains at position 3 (or at both positions 3 and 4). The most widely studied side-chains are n-alkyl substituents that can be easily introduced into the thiophene core by reaction of 3-bromothiophene with alkyl-Grignard reagents from alkyl halides [21]. 

Examples of the preparation of other heterocyclic magnesium compounds are shown in Tab. 3.6. The preparation of Grignard reagents derived from bromofuran, bromothiophene, and bromoselenophene has been reported, but no synthetic application has been attempted [106]. 

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