p-Nitrobenzenesulfonamide

Abstract

(A) p-Nitrobenzenesulfonamide (1) acts as a nitrogen source in the synthesis of heterocycles. Pyrroles, indoles, and carbazoles are accessible through successive annelation reactions with triflic acid.4 Török and co-workers found that the ratio of triflic acid to reagent determines the reaction outcome. Hence, p-Ns pyrrole is formed with 0.05 equiv of triflic acid whereas the indole derivative is formed with an equimolar amount of the acid. An excess of triflic acid (3.5 equiv) leads to the carbazole product. (Chemical Equation Presented) (B) Furthermore, 1 is a useful reagent in the assembly of non-aromatic heterocycles. Mukaiyama et al.5 described an efficient method for the preparation of pyrrolidines, piperidines, morpholines, and thiomorpholines. The products were formed in moderate to good yields. (Chemical Equation Presented) (C) Bolm and co-workers described efficient imination reactions of sulfides and sulfoxides using 1 as a nitrogen source, furnishing synthetically valuable sulfinimines and sulfoximines, respectively, in high yields. Both metal-catalyzed (Rh, Ag, Cu, Fe) 6a-d and metal-free variants of the reaction have been reported. 6e (Chemical Equation Presented) (D) Metal-catalyzed ring-opening reactions of methylene cyclopropenes with 1 were reported by Shi and co-workers. Depending on the metal catalyst used, the products of these transformations are either homoallylic10a or allylic10b sulfonamides. The latter can be deprotected to the corresponding allylic amines, which constitute interesting synthetic intermediates. (Chemical Equation Presented) (E) Taylor et al. reported a copper-catalyzed intermolecular hydroamination of olefins with sulfonamide 1.7 The hydroamination of styrene furnished 1-phenethylnosylamide in excellent yield. The reaction was found to be greatly enhanced by the addition of BINAP as a ligand as it was assumed that the ligand lowered the energy barrier of the process. The protocol was also found suitable for other alkenes such as norbornene. As with the styrenic substrates, the corresponding amine was formed in good yield. Interestingly, formation of the exo isomer was exclusively observed in this case. (Chemical Equation Presented) (F) Reddy and Davies achieved C-H activation reactions of alkanes with 1 and an adamantane-derived rhodium catalyst [Rh2(TCPTAD)4]. Both excellent yields and enantioselectivities in the C-H amination of indene were reported.8 (Chemical Equation Presented) (G) A copper-catalyzed one-pot procedure for aziridinations was recently reported by Kwong et al. 11 They used either 1 in combination with an oxidant [PhI(OAc) 2] or the corresponding preformed iminoiodinane [synthesized from 1 and PhI(OAc)2] as nitrene source for the aziridination of styrene and derivatives thereof. In combination with Evans' oxazoline ligand, very high yields and good enantioselectivities could be obtained. (Chemical Equation Presented) © Georg Thieme Verlag Stuttgart.