Microwave activated nitrogen

Active nitrogen has been a favorite subject of investigation by physicists for many years and, more recently, interest has also been aroused in its chemical behavior. However, serious difficulties have been experienced in this connection as a result of the presence of other active species besides nitrogen atoms. These have been difficult to identify with certainty and to separate kinetically. Substantial progress seems now to have been made in this respect and also it appears that complications are reduced when a microwave discharge is used to activate... 

Some controversy exists over the reactive species produced when nitrogen is passed through an R.f. or microwave discharge. Verbeke and Winkler investigated the reactions of active nitrogen with nitric oxide and ethylene and found that the amount of nitric oxide removed was greater than the maximum amount of HCN produced from ethylene. To account for this difference they postulated that vibrationally excited molecules were decomposing nitric oxide, viz. 

However, the nitrogen molecule has a r greater bonding energy than ammonia and is more difficult to dissociate into free atomic nitrogen active species. Consequently, the deposition rate is extremely slow. This can be offset by plasma activation at high frequency (13.56 MHz), by electron-cyclotron resonance (ECR), and with microwave activation. " ... 

An efficient one-pot procedure for the synthesis of ionic liquids based on nitrogen-containing heterocycles, imidazolium or pyridinium salts by following the conditions of green process has been developed (Aupoix et al., 2010). Imidazolium salts and DBU have been found to catalyze efficiently the benzoin condensation giving good yields within very short reaction time using solvent-free microwave activation conditions. 

The Clauson-Kaas pyrrole synthesis involving the reaction of primary amines with 2, 5-dialkoxytetrahydrofurans was traditionally carried out in refluxing acetic acid (AcOH). Extension to less activated nitrogen nucleophiles often necessitates the use of acidic promoters. Miles et al. (2009) reported that the synthesis of N-substituted pyrroles can be carried out under microwave conditions (10-30 min) using acetic acid or water without additional catalysts. The reaction is successful for all common nitrogen inputs in the case of acetic acid, where as benzamide and benzylamine are resistant to cyclocondensation under aqueous conditions. 

In a related study, Srivastava and Collibee employed polymer-supported triphenyl-phosphine in palladium-catalyzed cyanations [142]. Commercially available resin-bound triphenylphosphine was admixed with palladium(II) acetate in N,N-dimethyl-formamide in order to generate the heterogeneous catalytic system. The mixture was stirred for 2 h under nitrogen atmosphere in a sealed microwave reaction vessel, to achieve complete formation of the active palladium-phosphine complex. The septum was then removed and equimolar amounts of zinc(II) cyanide and the requisite aryl halide were added. After purging with nitrogen and resealing, the vessel was transferred to the microwave reactor and irradiated at 140 °C for 30-50 min... 

The microwave-assisted chemistry of a variety of aromatic heterocycles has been extended to the synthesis of fused molecules which share, at least, one heteroatom. In this area, the synthesis of nitrogen containing compounds has been actively investigated. All the compounds described below have been prepared in an effort to find compounds with interesting biological activity. 

Carbon nanotubes, microwave applications, 1, 334 Carbon-nitrogen bond activation, metal-mediated, HDN-relevant, 1, 794... 

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