Arylsulfonyl carbamates

Preparation of Hydrogel Arylsulfonyl Carbamates. To a solution of hydrogel (1-4.0 g) in dry pyridine (20-40 mL) was added eitherp-toluenesulfonyl Isocyanate (pTSI), 3.0 g, or p-nitro-benzenesulfonyl Isocyanate (p-NBSI), 0.5-3.0 g and the mixture was heated at 70 under nitrogen for 4 hr. The adduct was isolated by precipitation in benzene or ethanol. Repreclpltatlon from acetone or DMF yielded the desired products, IR (film) 3170 cm (-NH), 1530 cm" (-NO2), 1340, 1180 cm" (-SOj). The precise degree of substitution was determined by non-aqueous titration (Table II). 

To activate the hydrogel adducts for enzyme immobilization, it was necessary to reduce the nitro function to the corresponding amine. From the many techniques available to effect this modification, we selected sodium dithionite as the mildest procedure with the least potential problems with residual reagent. Since the hydrogels were quite hydrophilic it was possible to use a two phase solvent system (THF/H2O) to effect the reduction. The arylsulfonyl carbamates were reduced selectively under these conditions no reduction of p-nitrophenyl carbamate was observed. 

In contrast with the metallated 7V-[(arylsulfonyl)oxy]carbamates, it has been known since 1965 that ethyl N-[(p-nitrobenzenesulfonyl)oxy]carbamate 6e is a precursor of nitrene, thus a-elimination of p-nitrobenzensulfonate ion (NsO-) from the anion of ethyl Af-[(p-nitrobenzenesulfonyl)oxy]carbamate 6e leads at room temperature to the formation of (ethoxycarbonyl)nitrene 18 [12a] (Scheme 7). 

Arylsulfonylbenzimidoyl chlorides, with aminothiazoles, 50 Arylsulfonyl halides, 98, 115 Azide, with azothiazoles, 111 to carbamate, 16 Curtius rearrangement of, 15, 16 See also Sodium azide Azido thiazoles, 113 azidothiazole-thiazolotetrazole, 113 reactions of, 113... 

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