Sulfonyl isocyanates synthesis

Reductive ring opening of the [i-lactam 10 (X = O), obtained by [2 + 2] cycloaddition of chloro-sulfonyl isocyanate and tetraphenylcyclopentadiene followed by treatment with /7-cresol, with sodium hydride in anhydrous tetrahydrofuran yields 3,5,6,7-tetraphenyl-2//-azepin-2-one (11, X = O).41 Surprisingly, similar treatment of the reduced /Mactam 10 (X = H2) is reported to yield 3,5,6,7-letraphenyl-2//-azepine (11, X = H2), the first monocyclic 277-azepine to be isolated and characterized. Physical data for this compound, however, are inconclusive and attempts to reproduce this synthesis have failed.291... 

This reaction is typical for the synthesis of sulfonylureas it is mildly exothermic and proceeds smoothly in a variety of inert aprotic solvents. The product is usually obtained in very high yield, as a fine crystalline precipitate. The sulfonyl isocyanates are readily prepared from the substituted benzene sulfonamides by reaction with phosgene, Fig. 3, in the presence of an alkyl isocyanate, for example, butyl isocyanate in an inert solvent at 120 to 140°C according to the general procedure of H. Ulrich and A. A. R. Sayigh (Ref. 3). 

Synthesis of heterocycles, from acyl and sulfonyl isocyanates ... 

The synthesis of p. toluene sulfonyl isocyanate by phos-genation of p.toluene sulfonamide in presence of an alkyl isocyanate as the catalyst, generally n-butyl isocyanate, is well described in several patents and publications [Scheme... 

The 1,3,2-dioxastannolanes are important in organic synthesis because they can readily be derived from dialkyltin oxide and 1,2-diols, as in carbohydrates the reaction can be carried out in toluene in a few minutes under microwave irradiation.387 The dioxastannolanes can then be subjected to regioselective reaction with an electrophile such as an acyl chloride (Equation (140)) or sulfonyl chloride, or an isocyanate. The acylation or sulfonation can be carried out with catalytic amounts of the dialkyltin oxide, including the recoverable (C6F13CH2CH2)2Sn0.388... 

The A -acylation and A -sulfonylation of benzisoselenazol-3(2//)-one with carboxylic acid chlorides or sulfonyl chlorides is an efficient method for the synthesis of 2-acyl and 2-sulfonylbenzisoselenazol-3(2//)-ones 48 and 49 <1997SC283>. A reaction with formalin resulted in A -hydroxymethylbenzisoselenazol-3(2//)-one 50, while reaction with isocyanates yielded the 2-carbamoylbenzisoselenazol-3(2//)-ones 51 (Scheme 13) <2005UP3>. 

Synthesis of nitriles (2, 70). Lohaus has published two procedures which illustrate the use of chlorosulfonyl isocyanate for the preparation of nitriles. One, the preparation of 2,4-dimethoxybenzonitrile,8 illustrates the reaction of the reagent with aromatic compounds that readily undergo electrophilic substitution. Thus reaction of resorcinol dimethyl ether (1) with chlorosulfonyl isocyanate in methylene chloride gives the amide N-sulfonyl chloride (2), which on treatment with an amide9 gives 2,4-dimethoxybenzonitrile (3) in 95-96% yield with a purity of 98%. 

The field of organic chemistry has seen the most extensive use of polymeric materials as aids in effecting chemical transformation and product isolation. Insoluble polymer supports have been used as handles to facilitate these functions. As chemical reagents can be bound to an insoluble polymer carrier and used in organic synthesis [117,118], polymer-bound reagents can also be used to assist in the purification step of solution-phase reactions [119,120]. The latter are known as scavenger resins. These are added to the reaction mixture upon completion of the reaction in order to quench and selectively bind to the unreacted reagents or by-products. The polymer-bound impurities are then removed firom the product by simple filtration to obtain pure compounds. For example, aminomethylated poly(styrene-co-divinyl benzene) can be used to remove acid chlorides, sulfonyl chlorides, isocyanates, thiocyanates, and proton. Similarly, 2-Chlorotrityl resins have been developed for the attachment of carboxylic acids, alcohols. 

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