ChemInform Abstract: 1,3,2‐DIOXAZANES

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

“…20,58 The products of nucleophilic substitution of chlorine were obtained in reactions of the compounds 3a,c with sodium acetate, thiocyanate, and cyanide and also with a Grignard reagent. 10 When N-chloro-N-tert-alkyl-O-methylhydroxylamines 3a,c react with ammonia or amines, the corresponding N-methoxyhydrazine derivatives formed initially upon nucleophilic substitution of chlorine are unstable and decompose with elimination of MeOH. Thus the reaction of 3a with NH 3 gave a-chloroisobutyramide and diazene oxide 16.…”

“…Thus the reaction of 3a with NH 3 gave a-chloroisobutyramide and diazene oxide 16. 70 This outcome can be explained by assuming that the intermediate N-methoxyhydrazine derivative decomposes to give NH-diazene, which undergoes homolytic cleavage yielding a tert-alkyl radical. The reaction of the latter with the initial compound 3a followed by ammonolysis gives the final products.…”

“…In particular, N-alkoxy-N-tert-alkyl-O-alkylhydroxylamines (nitrosoacetals), 3,4 N,N-dialkoxy-O-alkylhydroxylamines (trialkoxyamines, orthonitrites), 5 and N-alkoxy-O-alkylhydroxylamines (NH-dialkoxyamines, orthoethers of nitrosyl hydride) 6 have been synthesised in this way, and oxidation of the latter compounds gave stable dialkoxyaminyl radicals 7 and their dimers (tetraalkoxyhydrazines). 7,8 The vast synthetic potential of N-halohydroxylamine derivatives is also due to the possibility of converting them into highly reactive intermediates such as N-alkoxynitrenes, 9 N-substituted N-alkoxyaminyl radicals, 7,10 and N-alkoxynitrenium ions. 5,11 Thus intramolecular cyclisation of N-chloro-O-alkylhydroxamates involving an aromatic substituent present in the acyl or alkoxyl fragment of their molecules, which occurs via intermediate N-acyl-N-alkoxynitrenium ions, is a general method for the synthesis of a large number of nitrogen-containing heterocycles.…”

“…They react with nucleophiles according to two competing pathways. 5,10,35,36 The addition of nucleophiles to the nitrenium centre [pathway (a)] is a reversible orbitally controlled reaction, which occurs in the case of `soft' nucleophiles with high-lying highest occupied molecular orbitals (HOMO). Conversely, dealkylation of the oxonium site [pathway (b)] is an irreversible charge-controlled reaction occurring in the case of `hard' nucleophiles having lowlying HOMO.…”

Conformational transformations of perhydro-1,3,2-dioxazine

“…The interest in structural studies of perhydro-1,3,2-dioxazines, saturated heteroanalogs of cyclohexane containing O-N-O moiety in the ring, is associated with the structural features largely defined by the high configurational stability of the nitrogen atom [1][2][3][4][5]. Perhydro-1,3,2-dioxazine was synthesized more than 25 years ago [4].…”