ChemInform Abstract: Asymmetric Nitrogen. Part 71. Geminal Systems. Part 45. N‐Halooxaziridines.

Abstract

ChemInform Abstract The N-chloro-and N-bromooxaziridines (II) and (III) are prepared by halogenation of the corresponding oxaziridines (I). (IIb) isomerizes upon standing to produce the chloronitroso compound (IV). Treatment of (IIc) with alcoholate gives cyclohexanone (V). (IIa) is coupled with the secondary amines (VI) or dimethyl sulfide (VIII), forming the tetrazenes (VII) and dimethyl sulfoxide (IX) respectively.

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

“…2-Haloxaziridines 8a ± e and 9a,d have been obtained in two ways: by halogenation of the corresponding NH-oxaziridines and by oxidation of N-chlorimine 10. 24,25,64,65 The chloroxaziridines 8a ± e can be distilled in vacuo without decomposition; in a pure state, they can be kept unchanged for 1 month at 0 8C, while as solutions in CDCl 3 , they are stable for 1 h at 100 8C in sealed tubes. The 2-bromoxaziridines 9a,d are stable for 1 weak at 0 8C in inert solvents; neat compounds can be stored at 778 8C but vigorously decompose to give the corresponding ketone at temperatures above 0 8C.…”

“…The 2-bromoxaziridines 9a,d are stable for 1 weak at 0 8C in inert solvents; neat compounds can be stored at 778 8C but vigorously decompose to give the corresponding ketone at temperatures above 0 8C. 65 Thermally stable 2-chloro-and 2-fluoro-perhalo-1,2-oxazetidines 11 have been prepared by halogenation of the corresponding 1,2-oxazetidines. 23,66 Dimethyl 2-chloro-1,2-oxazolidine-3,3-dicarboxylate 12 has been synthesised by the chlorination of 1,2-oxazolidine 13 20 and by the reaction of the methoxy-derivative 14 with SOCl 2 .…”

“…when the nucleophile attacks the nitrogen atom, an oxygen-containing anion becomes the leaving group. 65 The intermediate A thus formed decomposes yielding the corresponding ketone and a substituted N-haloamine B. The latter reacts with amines giving rise to tetrazene 25 (apparently, via diazenium salt and N-aminonitrene) or reacts with dialkyl sulfides with formation of N-chlorosulfimines 26.…”

“…The rearrangement of pure 8c at 0 8C proceeds slowly, whereas that in CDCl 3 at 60 8C occurs over 15 ± 20 min. 64,65 It was assumed 65 that this rearrangement occurs as intramolecular attack by chlorine on the carbon atom of the oxaziridine ring.…”

“…The transition state to the dissociative inversion is represented by a contact ion pair, because ionic mobility of chlorine is not manifested in reactions of 2-chloroxaziridines 8a ± d and 9a. 65 The driving force of ionisation is the orbital n O ± s* N ± Cl interaction, which results, according to the 2-chloroxaziridine structure optimised in the 6 ± 31G* basis set, in a substantially lengthened N ± Cl bond. 25 The introduction of a p-electron-withdrawing substituent to the nitrogen atom sharply decreases the barrier to its inversion, because p-conjugation is most efficient in the planar transition state.…”