1008-93-1Relevant academic research and scientific papers
The mechanistic origin of regiochemical changes in the nitrosative N-dealkylation of N,N-dialkyl aromatic amines
Teuten, Emma L.,Loeppky, Richard N.
, p. 1097 - 1108 (2007/10/03)
The regioselectivity of the nitrous acid mediated dealkylation of 4-substituted-N-ethyl-N-methylanilines is a function of the acidity of the reaction mixture. At high acidity deethylation predominates, whereas demethylation is the predominant reaction in nitrosamine formation at pH 2 and above. In some cases the regioselectivity of nitrosative dealkylation changes as the run proceeds. Through the use of the corresponding 4-nitroaniline as the primary substrate, CIDNP, kinetics, kinetic deuterium isotope effects and other transformations involving nitrosations with NO2 or NOBF4 in aprotic solvents, a new mechanism of tertiary amine nitrosation has been deduced and proposed to explain regioselective deethylation. The mechanism involves the oxidation of the substrate to the amine radical cation by NO +. This is followed by the abstraction of a hydrogen atom from the carbon adjacent to the amine nitrogen by NO2 to produce an iminium ion which reacts further to produce the corresponding aldehyde and the nitrosamine. Depending upon the acidity, this process competes with three other mechanistic pathways, two of which give the nitrosamine through the iminium ion, and one leads to the formation of C-nitro compounds. The competing pathways to nitrosamine formation involve NOH elimination from a nitrosammonium ion and deprotonation of the radical cation to give an α-amino radical which rapidly oxidized to the iminium ion. Predominant, but not highly regioselective demethylation occurs by these pathways. Nitro compound formation principally arises from the reaction of NO2 with the radical cation followed by deprotonation, but also occurs by para C-nitrosation followed by oxidation. The Royal Society of Chemistry 2005.
N-Alkyl-N-Cyclopropylanilines as Mechanistic Probes in the Nitrosation of N,N-Dialkyl Aromatic Amines
Loeppky, Richard N.,Elomari, Saleh
, p. 96 - 103 (2007/10/03)
A group of N-cyclopropyl-N-alkylanilines has been synthesized, and their reaction with nitrous acid in aqueous acetic acid at 0°C was examined. All compounds reacted rapidly to produce the corresponding N-alkyl-N-nitrosoaniline by specific cleavage of the cyclopropyl group from the nitrogen. The transformations were unaffected by the nature of the alkyl substituent (Me, Et, iPr, Bn). The reaction of 4-chloro-N-2-phenylcyclopropyl-N-methylaniline with nitrous acid gave 4-chloro-N-methyl-N-nitrosoaniline (76%), cinnamaldehyde (55%), 3-phenyl-5-hydroxyisoxazoline (26%), and 5-(N-4-chlorophenylmethylamino)-3-phenylisoxazoline (8%). Both the selective cleavage of the cyclopropyl group from the aromatic amine nitrogen and nature of the products derived from the cyclopropane ring support a mechanism involving the formation of an amine radical cation. This step is followed by rapid cyclopropyl ring opening to produce an iminium ion with a C-centered radical which either combines with NO or is oxidized.
Stereoelectronic Effects in Tertiary Amine Nitrosation: Nitrosative Cleavage vs. Aryl Ring Nitration
Leoppky, Richard N.,Tomasik, Witold
, p. 2751 - 2757 (2007/10/02)
The nitrosation (acetic acid) of N-(4-chlorophenyl)pyrrolidine gives at least 30percent N-(4-chloro-2-nitrophenyl)pyrrolidine while the corresponding aryldibenzylamine gives no nitration and only nitrosative dealkylation at nitrogen.This difference in reaction site has been probed with N-(4-chlorophenyl)diethylamine.This substance undergoes competitive ring nitration to N-(4-chloro-2-nitrophenyl)diethylamine (50percent) and nitrosative dealkylation to (4-chlorophenyl)ethylnitrosamine (50percent).The former compound nitrosates further to give (4-chloro-2-nitrophenyl)ethylnitrosamine.This substance denitrosates to give the corresponding secondary amine.The reactivity differences result from stereoelectronic factors controlling the amine nitrogen unshared pair delocalization into the aryl ring.This interpretation is supported by 13C NMR data and mechanistic arguments.
