Synthesis of alkyl-substituted ethyl 2,2':5',2'':5'',2'''-quaterthiophene-5-and 5-(biphenyl-4-yl)thiophene-2-carboxylates

[Figure not available: see fulltext.] Acylation of 2,2':5',2''-terthiophene and biphenyl gave 1-(2,2':5',2''-terthiophen-5-yl)dodecan-1-one and 1-(biphenyl-4-yl)dodecan-1-one, which upon treatment with phosphorus oxychloride and dimethylformamide were converted to 2-[(2,2':5',2''-terthiophen-5-yl)-chloromethylidene]dodecanal and 2-[(biphenyl-4-yl)chloromethylidene]dodecanal. The reaction of these compounds with ethyl 2-mercaptoacetate led to the formation of ethyl 3-decyl-2,2':5',2'':5'',2'''-quaterthiophene-5- and 5-(biphenyl-4-yl)-4-decylthiophene-2-carboxylates, which are of interest as building blocks for the synthesis of organic semiconductors. Ethyl 3-decyl-2,2':5',2'':5'',2'''-quaterthiophene-5-carboxylate was also obtained by palladium-catalyzed cross coupling of ethyl 5'-bromo-3-decyl-2,2'-bithiophene-5-carboxylate with 2,2'-bithiophene. © 2017, Springer Science+Business Media New York.