PARTIALLY FLUORINATED HETEROCYCLIC-COMPOUNDS .27. THE SYNTHESIS OF 4,5,6,7-TETRAFLUOROBENZO[C]THIOPHENE AND 4,5,6,7,8,9-HEXAFLUORONAPHTHO[1,2-C]THIOPHENE - SOME CHEMISTRY AND ELECTROCHEMISTRY

2,3,4,5,6-Pentafluorobenzyl methyl sulphoxide (6) is readily converted by butyl-lithium into 4,5,6,7-tetrafluorobenzo[c]thiophene (8) and 1,3,4,5,6,7,8-heptafluoro-2-naphthylmethyl methyl sulphoxide (9) in a similar manner gives a very low yield of 4,5,6,7,8,9-hexafluoronaphtho[1,2-c]thiophene (11) accompanied by the 7- and 8-butylated derivatives (12) and (13) respectively, and also 1,3,4,5,6,7,8-heptafluoronaphthalene-2-carbaldehyde (10). Compound (8) undergoes Diets-Aider addition reactions followed by sulphur elimination with dimethyl acetylenedicarboxylate and tetrafluorobenzyne to give the naphthalene and anthracene derivatives (14) and (15) respectively. With lithium propane-2-thiolate, compound (8) gives the 5-propan-2-ylthio and 5,6-bispropan-2-ylthio derivatives (16) and (17) respectively. Compound (8) is polymerised by SbF5-HFtopoly(1,3-dihydro-4,5,6,7-tetrafluorobenzo[c] - thiophene) (20). The electrochemical anodic oxidation of (8) has been studied extensively: polymer (20) is produced accompanied by a deep red material readily soluble in chloroform, which is not poly(4,5,6,7-tetrafluorobenzo[c]thiophene) (24).