3- Iodothiophene, reaction with metals

Thienylzincates are available using lithium di-zW-butyltetramethylpiperidinozincate (TMP-zincate) <1999JA3539> thus, ethyl thiophene-3-carboxylate is easily metallated at C(2) at room temperature, subsequent reaction with iodine giving ethyl 2-iodothiophene-3-carboxylate in 89% yield. Similarly ethyl thiophene-2-carboxylate gives the 5-iodo derivative in 62% yield. 

Since Li2Zn Bu4 could weU tolerate substrates bearing an acidic proton (Fig. 12), the protection-free synthesis of poly[3-(6-hydroxyhexyl)thiophene] (P3HHT), with hydroxyhexyl side chains, was also successful (Fig. 29). After halogen-metal exchange reaction of 2-bromo-3-(6-hydroxyhexyl)-5-iodothiophene with... 

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