N-Chloro and N-bromosaccharins: valuable reagents for halogenation of electron rich aromatics and cohalogenation of alkenes

Abstract

acetona aquosa fornecem as respectivas haloidrinas.N-Chloro-and N-bromosaccharins react with electron rich aromatic compounds (anisole, acetanilide, N,N-dimethylaniline) producing halogenated compounds. The reaction with N-bromosaccharin gives para-substituted compounds only, whereas N-chlorosaccharin produces orto and para mixtures (para isomer predominantly, ca. 4-5 : 1). The reactions of the N-halosaccharins with alkenes (cyclohexene, styrene, α-methylstyrene, and 1-hexene) give the corresponding halohydrins.

Studies on the Cohalogenation of Limonene With N-Halosuccinimides and N-Halosaccharins in Water. A Chemo-and Stereoseletive Preparation of (1s, 2r, 4r)-1,2-Epoxylimonene

“…In contrast to other results (17,18), the reaction oflimonene with NBSac was disappointing and NBS presented high chemo-and stereosectivity for the trans-1,2-epoxide. On the other hand, the reaction with NISac was the only case were 8,9-epoxylimonene predominated.…”

Application of N-halo reagents in organic synthesis

“…1,3-Dibromo-5,5-dimethylhydantoin (DBH, 6) with the commonly used trade name Brom-55, is a cream to palebrown powder which melts at [186][187][188][189][190][191][192] ºC. This reagent is sparingly soluble in carbon tetrachloride, benzene and water (0.06%, 1.1%, and 0.1% at 20 ºC, respectively).…”

“…Chlorinated and brominated aromatic compounds were prepared selectively by reaction of electron-rich aromatic compounds with NCSac or NBSac in good yields at room temperature (Scheme 137) [182]. …”

“…NCSac and NBSac were successfully applied for halogenation of electron rich aromatic compounds (anisole, acetanilide, N,N-dimethylaniline) [188]. The reaction with NBSac gave para-substituted compounds only, whereas NCSac produced a mixture of ortho and para isomers (Scheme 143).…”

“…The reactions of NCSac and NBSac with alkenes (cyclohexene, styrene, -methylstyrene, and 1-hexene) gave the corresponding halohydrins in H 2 O and acetone as solvent (Scheme 144) [188]. …”