N-chlorosaccharin (NCSac): A useful and alternative reagent in organic synthesis

Abstract

(A) de Souza and co-workers2 described an efficient procedure for halogenation of electron-rich aromatic compounds (anisole, acetanilide, N,N-dimethylaniline) with NCSac, leading to a mixture of ortho and para isomers (o/p = 4:1-5:1) in moderate to high yields. The same group reported a convenient regiospecific preparation of 5-chloroisatin with NCSac mediated by SiO 2, which leads under mild conditions in moderate yields to the product.3 (B) de Souza and co-workers2 described a co-halogenation procedure of alkenes which was easily achieved with NCSac in aqueous acetone at room temperature, leading to the corresponding chlorohydrins in high yields. The regioselectivity was very high and no regioisomeric products were detected. Dolenc and Sket4 reported a chlorofluorination of alkynes with NCSac, leading to products usually difficult to obtain.1 The reagent is more reactive than other ,N-chloroimides, but requires long reaction times, affording a mixture of vicinal chloro-fluoroalkenes, but only Markovnikov products. (C) Booker-Milburn and co-workers5a described a one-pot electrophilic Ritter-type reaction of NCSac with alkenes in acetonitrile, leading to two differents products, imidazolidine and aziridine, in moderate yields. (D) Iranpoor and co-workers5b reported a new, mild, regioselective and simpler methodology for the efficient conversion of epoxides into vicinal halo alcohols, symmetrical dichloride and unsymmetrical chloride compounds, using PPh3/NCSac in acetonitrile in good yields. In this method the conversion depends on the molar ratio and the type of N-haloimide used. (F) In addition to the previous cases, Bachhawat and co-workers6a also described an allylic and benzylic chlorination of organic compounds with NCSac and benzoyl peroxide or AIBN, as free radical source, leading to the corresponding products in moderate yields. © Thieme Stuttgart.