Microwave absorbents

Solvent Any Any Any Any Any (Modified) C02 Solvent with microwave absorbing component Any... 

AI methods may be used in various ways. The models may be used as a standalone application, e.g., in recent work on the design of microwave absorbers using particle swarm optimization (PSO).6 Alternatively, a computational tool, such as a finite element analysis or a quantum mechanical calculation, may be combined with an AI technique, such as an evolutionary algorithm. 

Goudos, S.K. and Sahalos, J.N., Microwave absorber optimal design using multiobjective particle swarm optimisation, Microwave Optic. Tech. Letts., 48, 1553, 2006. 

Ionic liquids, being polar and ionic in character, couple to the MW irradiation very efficiently and therefore are ideal microwave absorbing candidates for expediting chemical reactions. An efficient preparation of the 1,3-dialkylimidazolium halides via microwave heating has been described by Varma et al. that reduces the reaction time from several hours to minutes and avoids the use of a large excess of alkyl ha-lides/organic solvents as the reaction medium (Scheme 6.56) [26-28]. 

Alumina spheres polluted by carbon residues have been also reactivated by use of microwaves [33]. Their regeneration has been performed in a stream of air and in the presence of silicon carbide as an auxiliary microwave absorber. Microwave heat treatment led to full recovery of the catalyst in times varying from a half to a quarter of the conventional treatments. Regeneration of a commercial Ni catalyst (Ni/Al203) deactivated, presumably, by coke formation, by means of a flow of hydrogen or oxygen and water vapor under the action of microwave irradiation was, however, unsuccessful [34]. 

The [2+2+1] cycloaddition of an alkene, an alkyne and carbon monoxide is commonly known as the Pauson-Khand reaction. This transformation has been adopted many times in the synthesis of complex natural products and related compounds, which contain a cyclopentenone moiety, for example, prostaglandins. Two independent reports of this reaction appeared almost simultaneously in late 2002 by Iqbal and co-workers25 and Fisher and co-workers26, respectively. They not only used very similar substrate systems in their studies, but they also reached very similar conclusions Toluene was found to be the preferred solvent in this reaction, even though it is a very poor microwave absorber. A reaction time between 5 and 10 min, using dicob alto ctacar-bonyl or dicobalthexacarbonyl as the carbon monoxide source, and a temperature of 100-120°C resulted in high yields of the products. Fisher and co-workers used 20 mol% Co2(CO)8 and cyclohexylamine as an additive (Scheme 5.12), since this system had been used previously in order to allow a catalytic reaction. Iqbal and co-workers did not use cyclohexylamine, but instead used 1 equiv. of the carbon monoxide (Co2(CO)6) source. In both reports, the products were formed in 40-70% yield. 

Gorshenev, V.N., Bibikov, S.B. and Spector, V.N., Simulation, synthesis and investigation of microwave absorbing composite materials, Synthetic Metals, 1997, 86(1-3), 2255-2256. 

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