Dithienyl bromide

Applications of the aforementioned methodology are also found in the total synthesis of plagiochin D to link a 16-membered biaryl system [47], as well as to the intramolecular cyclization of di-benzyl halides [45, 48]. Additional examples include dithienothiophene (40) from dithienyl bromide 39 [49] and carbazole 42 from diarylbromide 41 [50]. 

To a solution of thienyl magnesium bromide prepared from 21.4 g of magnesium and 144 g of 2-bromothiophene are added 39.B g of ethyl 4-dimethylaminocyclohexylcarboxylate. The mixture is ailowed to warm to room temperature and stirred for an additional six hours. The reaction mixture is then decomposed with dilute ammonium chloride solution and extracted with ether. The combined ether extracts are extracted thoroughiy with 10% hydrochloric acid and the acid solution made alkaline with ammonium hydroxide. The aqueous solution is extracted with chloroform which is then washed with water, dried and evaporated to a residue in vacuo. Recrystallization of the residue from hexane yields Oi.O -dithienyl-4-dimethyl-aminocyclohexyl carbinol, melting point 156°C to 157°C after recrystallization from benzene. 

The submitters have also prepared 2,2 -dithienyl sulfide in 34% yield by condensation of 2-thiophenethiol with 2-bromothiophene in the presence of cuprous oxide in a quinoline-pyridine mixture. Challenger and Harrison6 have obtained 2,2 -dithienyl sulfide in 50-55% yield by treatment of 2-thienyl-magnesium bromide with excess sulfur. This sulfide may also be obtained in 20% yield by condensation of thiophene with sulfur monochloride, followed by pyrolysis of the resultant disulfide.7... 

The corresponding bromide forms fine white crystals, M.pt. 191 C., from toluene solution, and is obtained by treating an acetone solution of mercurj 5 5"-dichloro-2 2 -dithienyl with mercuric bromide. 

Bromomercuri-2 -methylthiophene.—To prepare this substance mercury 5 5 -dimethyl-2 2 -dithienyl (1-97 grams) and 1 8 grams of mercuric bromide in 100 c.c. of acetone are rapidly brought to the boil, then cooled in ice. The bromide is precipitated by the addition of water. Yield 3-5 grams. It crystallises from ethyl acetate in shining, white needles, melting at 179° to 180° C., and ha dng the usual solubilities. 

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