2,4-dinitrobenzenesulfonamide

The a- and /3-cyclodextrins have been found to accelerate the Smiles rearrangement of 4-nitrophenyl salicylate. The reaction of 2,4-dinitrobenzenesulfonamide with acyl chlorides in the presence of excess triethylamine has been found to produce the corresponding nitrile in good yield. Mechanistic studies have indicated that the reaction proceeds via a Smiles rearrangement of the initially formed iV-(2,4-dinitrobenzenesulfonyl)amide to form the nitrile, 2,4-dinitrophenol, and sulfur dioxide (see Scheme 12). l-Chloro-3-fluorophenothiazines have been prepared by Smiles rearrangement of 3-chloro-5-fluoro-2-formamido-2 -nitrophenyl sulfides in alcoholic... 

Nitro- or 2,4-dinitrobenzenesulfonamides of primary or secondary amines can be hydrolyzed under mildly basic conditions, and are increasingly being used for amine protection (see Section 10.1.10.7 [123,139,140]). /V-(2-Nitrobenzenesulfonyl)amino acids can be used as an alternative to TV-Fmoc amino acids for the solid-phase synthesis of peptides [141]. Deprotection is achieved by treatment of the polystyrene-bound sulfonamide with a solution of PhSH (0.5 mol/L) and K2C03 (2 mol/L) in DMF for 10 min at room temperature [141], conditions that do not lead to cleavage of esters (e.g. of the Wang linker) or to racemization. The condensation of polystyrene-bound sulfinamides H2N-SO-Pol with aldehydes yields /V-sulfinylimines, which add... 

An interesting version of the rearrangement [76] is presented in Scheme 51. The base-induced reaction of 2,4-dinitrobenzenesulfonamide with various acyl chlorides provides AT-(2,4-dinitrobenzenesulfonyl) acylamide derivatives 159 that rearrange and fragment in situ to afford the respective nitriles 160. The reaction has been used for derivatization of complex crown ethers. 

The vindoline synthesis required prior preparation of the amine coupling partner, the 2,4-dinitrobenzenesulfonamide 713, which was prepared from the pent-anal 710, as shown in Scheme 43. A notable feature of this route was the enzyme-mediated resolution of the cyanohydrin acetate 711, via enzymatic hydrolysis to selectively afford a diastereomeric mixture of only the (5)-cyanohydrins 712. 

Alternatives to DNB as tt acceptor included A-ethyl-2,4-dinitrobenzenesulfonamide and A-methyl-pentafluorobenzamide. F-NMR upfield shifts in the resonances of the three magnetically distinct fluorine atoms, when the latter tt acceptor molecule was mixed with DMAC, are 0.3362, 1.6754 and 0.9570 ppm. This data is the first to be reported where fluorine resonance serves as a proof of complexation. When considering the goal of the current research, this may be useful since fluorine and trifluoromethyl substituted aromatics are tolerated by the human body more than nitro aromatics [52,53]. 

Based on a related mechanistic concept, a transformation of acyl chlorides into nitriles was reported 15 years ago using 2,4-dinitrobenzenesulfonamide 100 under basic conditions fScheme 19.5517 In this reaction, the intermediate sulfonimidamide anion 101 undergoes a Smiles rearrangement, forming the nitrile functional group after SO2 extrusion and loss of the phenolate moiety. 

Deprotection of 2,4-Dinitrobenzenesulfonamides. Facile deprotection of sulfonamides (4) can be achieved by treatment with excess / propylamine or HSCH2CO2H and EtsN to give the desired secondary amines (5) in quantitative yields (eq 2). The latter procedure is more convenient in that the by-product, 2,4-dinitrophenylthioacetic acid, can be easily removed by washing the etherial layer with an aq NaHCOs solution. This deprotection method was advantageously used in selective deprotection of 2,4-dinitrophenylsulfonamides in the presence of a nitrophenyl-sulfonamide group in the synthesis of polyamines (eq 3). ... 

Synthesis of Nitriles from Acyl Chlorides. Acyl chlorides can be converted into the corresponding nitriles in good yields by reaction of 2,4-dinitrobenzenesulfonamide and triethylamine in THF. Presumably, the reaction with 2,4-dinitrobenzenesulfonamide and acyl chloride involves a Smiles rearrangement to give a nitrile, 2,4-dinitrophenol, and sulfur dioxide (eq 8). 

Tomkinson et al. developed a novel deprotection/amide formation sequence from Mitsunobu reaction products incorporating the 2,4-dinitrobenzenesulfonamide functionality. Treatment of the sulfonamide derivative 174 with thiobenzoic acid or a substituted analog thereof in the presence of cesium carbonate in DMF led to the isolation of the amide product 175 in very good yields. 

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