Thiophenes continued ring synthesis

The methods for de novo thiophene ring synthesis described in this chapter, many of which have been known for some time, continue to dominate the field. No doubt there will be future innovations, but the range of substituted thiophenes which can already be readily produced by these known methods, taken with the well-developed substitution chemistry of thiophenes (Chapter 3, Thiophene Substitution Chemistry), makes accessing any desired thiophene-containing compound a relatively well-developed art. 

The thiophene ring is a common building block for novel oligomeric and polymeric materials. The synthesis of monodisperse thiophene oligomers continues to be widely studied and the preparation of one class of oligomers, oligothienylenevinylenes <00CEJ1698,... 

Syntheses of Thiophens from other Ring Systems.— There has been continued interest in the use of 1,3-oxathiazolium salts for the synthesis of thiophens in high yields. From the 2-aryl-substituted derivatives (56), 3-amino-thiophens (57) are obtained in the reaction with malononitrile in the presence of base, and 3-hydroxythiophens (58) and (59) with methyl cyanoacetate and... 

The reaction between 2-nitrothiophen and secondary aliphatic amines leads most probably to the ring-opened product (213). Raney-Nickel desulphurization continues to play an important role in the structure determination of thiophen derivatives, and for the synthesis of macrocyc-lic compounds, such as a-alkylcycloalkanones, amino-lactams of aliphatic diaminocarboxylic acids, and of dethiobiotin. The nickel boride catalyst (NiBo), prepared from nickel(ii) chloride and sodium borohydride in methanol, gives olefins in 50—55% yield. From (214) a mixture of methyl... 

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