Synthesis and properties of N-(2,2,2-tribromoethylidene)-4-chlorobenzenesulfonamide

The present work continues a systematic study to find efficient and accessible methods for the synthesis ofN-sulfonylimines of polyhaloaldehydes and to analyze their properties. In the reaction of N,N-dichlorobenzene sulfon-amide with tribromoethylene, N-(2,2,2-tribromoethylidene)amide of 4-chlorobenzenesulfonic acid was obtained for the first time with a quantitative yield at boiling water bath temperature in carbon tetrachloride medium. The infrared spectra of N-(2,2,2-tribromoethylidene)-4-chlorobenzenesulfonamide reveal the absorption bands of sulfonic (1360 and 1165 cm -1 ) and NH (3275 cm -1 ) groups, while the 1 H NMR spectra show a signal for azomethine protons within the region of 8.3–8.6 ppm. The 13 C NMR spectra exhibit a signal for the CBr 3 group within the region of ~31–43 ppm, while the signal characteristic of the CBr 2 Сl group within the region of ~53–56 ppm is absent. This means that no imine of dibromochloroacetic aldehyde is formed during the reaction. Thus, an efficient method for the synthesis of N-(2,2,2-tribromoethylidene)-4-chlorobenzenesulfonamide was developed, and the chemoselectivity of this reaction was found to depend on the process temperature. It was shown that N-(2,2,2-tribromoethylidene)-4-chlorobenzenesulfonamide has amidoalkylating properties. A reaction of N-(2,2,2-tribromoethylidene)-4-chlorobenzenesulfonamide with benzene, toluene, anisole, and 2-chlorothiophene in the presence of an acid catalyst yielded p-substituted aromatic derivatives and 2,5-substituted thiophene derivatives. Infrared spectroscopy and NMR spectroscopy ( 1 H, 13 C) revealed that the substitution reaction proceeds regioselectively. All the obtained products were isolated in pure form as powders soluble in polar organic solvents and insoluble in water. The yields of 4-chloro-N-(1-phenyl-2,2,2-tribromoethyl)-benzenesulfonamide, 4-chloro-N-[1-(4-methylphenyl)-2,2,2-tribromoethyl]-benzenesulfonamide, 4-chloro-N-[1-(4-methoxyphenyl)-2,2,2-tribromoethyl]-benzene-sulfonamide, and 4-chloro-N-[2,2,2-tribromoethyl-1-(5-chloro-2-thienyl)ethyl]-benzenesulfonamide amounted to 74, 72, 64, and 74 %, respectively.