Fluorosulfonyl isocyanates

Many synthetic processes have been described for acesulfame. One involves the condensation of a halosulfonyl isocyanate and an acetylene or a ketone (67,68). The fluorosulfonyl isocyanate can be prepared by reaction of sulfuryl diisocyanate with fluorosulfonic acid (69). 

Bond formation between oxygen and sulfur occurs when the AM2-hydroxyethyl)thiourea (155) is oxidatively cyclized with bromine to give the 1,2,4-oxathiazine (3) (77TL4245), and when the intermediate (183), from reaction of ketones with fluorosulfonyl isocyanate (FSI), is cyclized with base to give (184) <80AG(E)13l). 

Analogous reactions with both chloro- and fluorosulfonyl isocyanates are also reported (166). Reactions of SF5NCO with trimethylorthofor-mate, HC(OMe)3, give SF5NHC(0)C(0Me)3 and SF5N(CH3)C(0)0Me (150). The formation of the latter probably takes place via the same mechanism as has been proposed for a similar reaction with chlorosul-fonyl isocyanate (167). 

Acesulfame potassium is synthesized from acetoacetic acid tert-butyl ester and fluorosulfonyl isocyanate. The resulting compound is transformed to fluorosulfonyl acetoacetic acid amide, which is then cyclized in the presence of potassium... 

On the other hand, the 1 1 exojendo mixture of 8-methylspiro[2.5]octa-4,6-diene-tricar-bonyliron complex 54 was converted to the complex of 8-methylenespiro[2.5]octa-4,6-diene 55 via hydride abstraction and deprotonation.Attempts to decomplex the ligand from the rather sensitive complex failed however, a cycloadduct with fluorosulfonyl isocyanate gave a stable derivative 56. 

The difference in reactivity of halosulfonyl isocyanates is shown in equation 84. The reaction of 146 with 2-butyne gave the [2 + 2]adduct in moderate yield, which was hydrolyzed to 163 by treatment with methanol. In contrast, 2 equivalents of fluorosulfonyl isocyanate reacted with 2-butyne to give a six-membered heterocycle, which on hydrolysis rearranged to 16279. 

Butyne allowed to react several days at room temp, with 2 moles fluorosulfonyl isocyanate in a chlorohydrocarbon solvent 5,6-dimethyluracil-l,3-disulfo-fluoride. Y 83%. F. e. s. K. Clauss and H. Jensen, Tetrah. Let. 1970, 119 s. a. K.-D.Kampe, ibid. 1970, 123. 

R. Appel, H. Rittersbacher, Chem. Ber. 1964,97, 849-851. Reaction of sulfuryl diisocyanate with halosulfuric acids. A simple method for the preparation of fluorosulfonyl isocyanate and imidobis(sulfuryl fluoride). 

Both alkyl- and aryl isocyanates insert readily into As-N bonds In contrast, As(NMc2)3 reacts with fluorosulfonyl isocyanate to give a rearrangement product 322. ... 

In the [2+2] cycloaddition reaction of thioketenes with chloro- and fluorosulfonyl isocyanates the [2+2] cycloadducts are not isolated, but j8-thiolactams resulting from the hydrolysis of the halosulfonyl groups are obtained. 

Solns. of N,N-di-terf-butylsulfinodiimine and fluorosulfonyl isocyanate in dry methylene chloride dropped simultaneously at -78° into vigorously stirred methylene chloride, and warmed to room temp. N- r/-butyl-N -(fluorosulfonyl)-sulfinodiimine. Y 77%. F. e. s. R. Appel and M. Montenarh, B. 109, 2437 (1976). 

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