Original scientific paper

On the Synthesis of Isomeric Dithiophene Analogues of Phenathridine- N-oxides

Salo Gronowitz ; Division of Organic Chemistry 1, Chemical Center, University of Lund, P.O. Box 124, S-221 00 Lund, Sweden
Anna-Britta Hornfeldt ; Division of Organic Chemistry 1, Chemical Center, University of Lund, P.O. Box 124, S-221 00 Lund, Sweden
Youhua Yang ; Division of Organic Chemistry 1, Chemical Center, University of Lund, P.O. Box 124, S-221 00 Lund, Sweden

Abstract

Six of nine o,o'-formylnitrobithienyls have been synthesized
by the tetrakis(triphenylphosphine)palladium(O)-catalyzed coupling
of the three o-bromonitrothiophenes with two of the three o-formylthiopheneboronic acids with sodium carbonate or sodium bicarbonate as base and an ethylene glycol dimethyl ether-water
mixture as solvent. In the reaction with 3-formyl-2-thiopheneboronic
acid, the coupling was carried out by using triethylamine
as base and N,N-dimethylformamide as solvent in an attempt to
avoid the facile deboronation of 3-formyl-2-thiopheneboronic acid,
but without success. Reduction of the o,o'-formylnitrobithienyls gave high yields of the N-oxides of the six isomeric dithienopyridines, which are analogues of phenanthridine-N-oxide. A direct synthesis of one of
the dithienopyridines, dithieno[2,3-c:2',3'-c]-pyridine, was achieved
by the palladium(O)-catalyzed coupling of 2,3-dibromothiophene
with 2-formyl-3-thiopheneboranic acid to 3-bromo-2'-formyl-2,3'-
-bithienyl, which was transformed to the 3-azido-2'-formyl-2,3'-
-bithienyl, which upon reduction with hydrogen sulfide underwent
ring closure to the phenanthridine analogue.

Keywords

Hrčak ID:

177596

URI

https://hrcak.srce.hr/177596

Publication date:

16.5.1986.

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