76300-20-4Relevant academic research and scientific papers
N-nitroso-N,O-dialkylhydroxylamines: Preparation, structure, and mechanism of the hydronium ion catalysed solvolytic nitrous oxide extrusion reaction
Bhat, J. Ishwara,Clegg, William,Maskill, Howard,Elsegood, Mark R.J.,Menneer, Iain D.,Miatt, Peter C.
, p. 1435 - 1446 (2007/10/03)
Eleven N-nitroso-N,O-dialkylhydroxylamines, RN(NO)OR′, have been prepared and the mechanisms of their hydronium ion catalysed solvolyses in aqueous solution which liberate nitrous oxide have been investigated. All reactions are first-order in substrate and first-order in hydronium ion, and the second-order rate constants at 25°C vary over a range of less than 140 in spite of considerable variation in substrate structure (R ranges from methyl to 4-methoxybenzyl to 2-adamantyl, for example) and changes in solvent composition (water with up to 50% methanol or 66% acetonitrile). Enthalpies and entropies of activation are qualitatively similar throughout the range (ΔH?= 72-93 kJ mol-1 and ΔS? = -19 to -57 J K-1 mol-1) which, with the product analyses, are accommodated by a mechanism involving pre-equilibrium protonation of the substrates followed by rate-limiting dissociation to give RN2O+ and HOR′. The oxodiazonium ion intermediate, RN2O+, then dissociates further to give the carbenium ion intermediate, R+, or suffers direct nucleophilic displacement of N2O by solvent (the external nucleophile) or by R′OH (the internal nucleophile liberated in the initial fragmentation). The carbenium ion, R+ (if formed), suffers nucleophilic capture either by solvent or by R′OH. When acetonitrile is the co-solvent (rather than methanol) for the N-(2-adamantyl) substrate 3g, the product of the Ritter reaction, 2-acetamidoadamantane, is detected. These nitrous oxide liberating reactions are compared with the nitric oxide liberating reactions of related N-nitrosohydroxylamines, and the origin of the difference between them is identified. The N(1)-nitroso group in the N,O-dibenzyl compound 3c is shown by X-ray crystallography to be essentially coplanar with the C and O atoms also bonded to N(1).
C-Nitroso compounds. Part XXXIII. Reaction of α-chloronitrosoadamantane with Grignard reagents
Schenk, C.,Beekes, M. L.,Boer, Th. J. de
, p. 246 - 252 (2007/10/02)
The reaction of α-chloronitrosoalkanes with aliphatic and aromatic Grignard reagents RMgX has been studied using the model compound α-choronitrosoadamantane (AdClNO)1.In addition to adamantanone oxime 7 (4-60percent) and the adamantanone oxime ether 8 (trace -28percent), the expected nitrone 2 is formed.The nitrone can be isolated for synthetic purposes using a non-chromatographic procedure in widely varying yields (6-87percent).The structure of all nitrones has been determined using spectroscopic techniques.Formation of oxime and oxime ether has been explained with the mechanism outlined in Scheme 3.This also accounts for the drastic changes in product distribution with the nature of the Grignard reagent.The mechanism involves nitrone formation via polar 1,2-addition of the Grignard reagent to the nitroso group, and single electron transfer (SET) from the Grignard reagent to the nitroso compound which leads to an iminoxy radical together with radical R..The latter combines with the multident iminoxy radical on nitrogen and oxygen (not on carbon) producing the nitrone and the oxime ether.Disproportionation can result in the formation of oxime.The oxime can also be formed when iminoxy radicals accept an electron from the Grignard reagent.As the electron donating power is strongly influenced by the nature of the Grignard reagent (i.e.SET vs. polar addition), widely varying product distributions are obtained.The phenyl Grignard reagent is amongst the poorest of electron donors, and therefore gives almost exclusively nitrone by polar 1,2-addition.Since nitroso compounds are normally excellent free radical scavengers, it is difficult to explain why trapping of transient radicals R. by the nitroso compound, followed by loss of halogen, appears to be relatively unimportant as a route to nitrone (Scheme 3, reaction iii).The formation of dibenzyl (42percent) from the reaction of AdClNO 1 with benzylmagnesium bromide is equally remarkable.
