Dimethyl disulfide dibromide

Pyrrole 843 (R = Me) was formed in moderate yield (30%) by treatment of 3,4-dibromo pyrrole 842 with Bu"Li and then with dimethyl disulfide. Pyrrole 843 (R = Bu") was prepared according to Klingsberg s method, by treatment of dibromide 842 with copper(l) -butanethiolate in a mixture of quinoline and pyridine to give the desired product in 33% yield. In both cases, the monosubstituted derivatives 844 were obtained as intermediates in 45% and 10.5% yields, respectively. 

Methoxyphenyl Tellurium [0,0 -Dimethyl dithiophosphate] Dibromide Dry ammonium 0,0 -dimethyl dithiophosphate (42 mg, 0.22 mmol) is added to a slurry stirred solution of 103 mg (0.22 mmol) of 4-methoxyphenyl tellurium tribromide in 5 ml carbon disulfide. The mixture is stirred at 20° for 0.5 h and then filtered. The solvent is evaporated from the filtrate at 0° under reduced pressure. The gummy yellow residue is recrystallized from chloroform/hexane (1 1) at — 4". The crystals are collected and dried under reduced pressure yield 74% m.p. 121°. 

When tetrahydropyridopyrimidine-3-carboxylate 562 (R = COOEt, R1 = H) was treated with carbon disulfide in the presence of potassium hydroxide at 25-30°C, salt 569 was obtained in good yield (79NEP79/ 3401 82USP4321377). The alkylation of569 with dimethyl sulfate and with ethylene dibromide in ethanol afforded 9-dithioester 570 and 9-(dithiolen-2-ylidene) derivative 571, respectively. When 569 was heated in acetic anhydride for 2 hours, bis product 572 was obtained in 57% yield. 9-Imidazolidine derivative 573 was prepared from both iminium chloride 563 (R = COOEt, R1 = H, R2 = Me) and 9-dithioester 570 by treatment with ethylenediamine (Scheme 37) (79NEP79/3401 82USP4321377 83MIP1). 

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