B. Ayres, S. W. Longworth, J. Mcomie
Aug 1, 1975
Citations
1
Influential Citations
18
Citations
Journal
Tetrahedron
Abstract
Abstract Starting from 2,5-dichlorothiophen many new 3,4-disubstituted thiophens have been made including the dialdehyde. Treatment of this with phosphorus pentabromide could be made to give 2,5-dichloro-3- dibromomethylthiophen-4-aldehyde, 2,5-dichloro- or 2-bromo-5-chloro-3,4-bisdibromomethylthiophen. the latter two compounds reacted with sodium iodide to give the corresponding cis - and trans -3,4-dibromo cyclobuteno[ c ]thiophen derivatives ( 18–21 ). Reaction of trans -3,4-dibromo-2,5-dichlorocyclobuteno[ c ]thiophen with N-bromosuccinimide resulted in fission of the 4-membered ring regenerating 2,5-dichloro-3,4-bisdibromomethylthiophen. When 2,5-dichloro-3,4-di-iodothiophen was treated with butyl-lithium followed by dimethylsulphate it gave 2,5- dichloro-3,4-dimethylthiophen together with a low yield of a red compound which is considered to be a dichloro dimethyl derivative ( 11 ) of bisthiophenindigo. Several unsuccessful approaches to the synthesis of dithiophen analogues of biphenylene are outlined. These included heating various 3,4-di-iodothiophens and 4,4′-di-iodo-3,3′-bithienyls with copper as well as the flash vacuum pyrolysis of the latter compounds, of thiophen-3,4-dicar☐ylic anhydrides and of 2,5-dichloro-3-iodothiophen-4-car☐ylic acid.