Electrochemical behavior of aromatic amines protected by the nitrobenzenesulfonyl group

Abstract

The electrochemical reduction of aniline protected by the 4-, 3-, or 2-nitrobenzenesulfonyl group in N, N-dimethylformamide (DMF) at a vitreous carbon electrode is reported. The compouads are reduced in three cathodic steps. The first reduction step at about -0.85 V vs. SCE occurs with the formation of an unstable anion radical, which decomposes via N-H bond cleavage. Reduction of this sulfonamide anion occurs at -1.16V for para and meta isomers and at -1.48V for the ortho isomer. The third cathodic step occurs at higher cathodic potentials. The B-H bond cleavage is always the preponderant process. The mechanisms of the reduction are discussed.

Electrochemical behavior of a nitrobenzenesulfonyl derivative of aniline in aqueous solution

“…Al though cath odic deprotection in aprotic me dia forms the ba sis of a use ful pre para tive pro ce dure for the re moval of the nitrobenzenesulphonyl group from amines [3][4][5] , our find ings in di cates that the cleav age of the S-N bond in the N-phenyl-4-nitrobenzenesulphonamide in aque ous so lution is not sig nif i ca tive un der reductive con di tions.The ease with which the ni tro group is re duced to a hydroxylamine group in aque ous so lu tion makes the electro chem i cal unprotection method un suit able for amines pro tected by the nitrobenzenesulphonyl group.…”

“…The fore go ing ex per i ments show that in N-phenyl-4-nitrobenzene sulphonamide, in con trast to the re sults ob tained in an aprotic me dium [3][4][5] , the cleav age of S-N; N-H or C-S bonds are not pre dom i nat ing in the process in aque ous so lu tion. On the other hand, as with other nitroaromatic com pounds [9][10][11][12][13][14] , the over all course of the reduc tion of the N-phenyl-4-nitrobenzenesulphonamide in aque ous so lu tion prob a bly in volves the re duc tion of the nitro group to the hydroxylamine in a four elec tron pro cess.…”

“…The cath odic cleav age of amines and amino-acids protected by a nitrobenzenesulphonyl group has been elec trochem i cally in ves ti gated in re cent years with the aim of study ing a sim ple method of unprotection of the amino func tional group [3][4][5] . In these stud ies, the re duc tion of N-butyl-2-, 3-or 4-nitro-benzenesulphonamide 3 ; N,N-di-n-butyl-4-nitrobenzenesulphonamide; and N-phenyl -2-, 3-, or 4-nitrobenzenesulphonamide 5 , and 4-nitrobenzenesulphonyl-alanine and 4-nitrobenzenesulphonyl-phenylalanine in N,N-dimethyl-formamide 4 has been in ves ti gated. In pre vi ous pa pers it is pos si ble to as cer tain that the elec trochem i cal re moval of the nitrobenzenesulphonyl group in an aprotic sys tem oc curs by S-N bond cleav age (es sen tial for unprotection of amine or aminoacid), but it is greatly affected by the pro ton avail abil ity and fea tures of the R group of the re sult ing amidic group.…”

Treatment Methods for the Remediation of Amines: A Review

“…The electrochemical degradation of atrazine in aqueous solution at a platinum electrode has been reported recently with its partial degradation into cyanuric acid at 25°C, but complete at 60° C in 4 hours and no mineralization had been observed [45]. A similar electrochemical reduction of aniline, shielded by the 4-, 3-, or 2-nitrobenzenesulphonyl group in N,N-dimethylformamide (DMF) at a vitreous carbon electrode, has been studied [46]. The compounds were reduced in three cathodic steps.…”