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 1H NMR spectra show a signal for azomethine protons within the region of 8.3–8.6 ppm. The 13C NMR spectra exhibit a signal for the CBr3 group within the region of ~31–43 ppm, while the signal characteristic of the CBr2Сl 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 (1H, 13C) 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.