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DOI: 10.1055/s-2000-6410
Synthesis of Anthryl-Substituted Bithienylpyridines and their N-Methylpyridinium Salts
Publication History
Publication Date:
31 December 2000 (online)
The synthesis of bithiophenes with anthracene and pyridine as terminal groups is described. 3- and 4-thienylpyridines 3, derived from thiopheneboronic acid 1 and the respective bromopyridines 2a, b, were coupled with 2-(9-anthryl)-5-iodothiophene 4 to give the isomeric (9-anthryl)bithienylpyridines 5a, b. In order to introduce a methylene spacer between the donor anthracene and bithiophene, 5-(2,2′-bithienyl)magnesium bromide 7 was reacted with 2 to yield the bithienylpyridines 9a, b. The reaction of 9 with 9-hydroxymethylanthracene 10 gave 3- and 4-(9-anthrylmethyl)bithienylpyridines 11a, b. The linkage of pyridine to bithiophene via a methylene spacer was reached by reacting lithiobithiophene with the isomeric pyridinecarbaldehydes 14a, b. Dehydroxylation of the resulting carbinols 15a, b with NaBH3CN/ZnI2, however, afforded the N-cyanoborane adducts 16a, b, which were transformed to the desired 3- and 4-(bithienylmethyl)pyridines 18a, b by heating either in EtOH or in 6 N HCl. Pyridines 5, 9, 11, and 18 were methylated with CF3SO3Me in CH2Cl2 or Et2O as solvent to yield the corresponding pyridinium triflates 6, 12, 13, and 19 in high purity.
aryl-aryl coupling - donor-acceptor systems - electron transfer - oligothiophenes