Communication 23. Reaction of N,N-dialkoxyamines with electrophiles

Geminal oxygen–nitrogen–halogen systems.N-Halohydroxylamine derivatives

“…They have been prepared by chlorination of the corresponding hydroxylamines 4, 48, 52 ± 57 and by cleavage of N-tert-alkyl-N-methoxy-O-methylhydroxylamine 4 upon treatment with acyl chlorides or chlorotrimethylsilane. 58,59 The compound 3a in a pure state decomposes over a period of 12 h at 20 8C, 4 whereas 3c can be distilled in vacuo and remains unchanged in solution (CCl 4 ) for at least a month. 4 The only known acyclic N-bromo-N,O-dialkylhydroxylamine 6 was synthesised by bromination of the oxime O-ether 5 in the presence of CsF.…”

“…60 The attempt to prepare N-bromo-N-tert-alkyl-O-methylhydroxylamine 7 was unsuccessful; this compound is unstable and undergoes further transformations under the reaction conditions. 59 Acyclic fluorinated N-fluoro-N,O-dialkylhydroxylamines have been reported. These derivatives have been synthesised by fluorination of the corresponding NH-hydroxylamines, 61 oxime O-ethers, 60 and trifluoronitrosomethane 62 and by photochemical reaction of N,N-difluoroamines with trifluoromethyl peroxide.…”

“…In some cases, the compounds 16 are the only reaction products. 4,59 The intramolecular version of this reaction has been used to synthesise N-methoxy-1,2-oxazolidine 17; the product was obtained in 45% yield. 4,52 Methanolysis of 2-chloro-1,2-oxazolidine 12 also proceeds smoothly.…”

“…N-chloro-N-tert-alkyl-O-methylhydroxylamine 3a 59 and oxazolidine 12 20 react with gaseous HCl to give the corresponding hydrochlorides 28 and 29.…”

“…The reaction of the compound 3a with CF 3 COCl affords N-methoxytrifluoroacetamide 30, the hydrochloride 28, and methyl N-methoxycarbamate 31. 59 Presumably, the trifluoroacetamide 30 is formed upon decomposition of the N-chloro-N-methoxy-N-trifluoroacetylammonium salt formed intermediately. N-Methoxcarbamate 31 results from 1,2-rearrangement of the compound 3a, accompanied by migration of the methoxycarbonyl group, and subsequent hydrolysis of the resulting intermediate C by traces of water.…”