Oxidation-reduction reactions microwave-assisted

Eberlin also studied the Heck reaction of aryltellurides [45] and Svennebring [19] reported the identification of three types of cationic, catalytic intermediates (Fig. 4A-C) in the microwave-assisted, phosphine-containing Heck arylation of electron rich olefins. In the latter case the authors support a Pd(0)/Pd(II) cycle as opposed to a Pd(II)/Pd(IV) cycle based on ESI-MS evidence for reduction of the palladium(II) precatalyst to Pd(0) by the ligand, and oxidative addition of the aryl substrate to a Pd(0) species. None of the expected Pd-bound olefin intermediates were observed however, this is often the case either because the olefin-bound species is neutral or because OA (oxidative addition) is the turnover-limiting step and the subsequent steps occur too quickly to be observed by the sampling method (in this case sampling included quenching and dilution of samples from a reaction vessel). 

Nitrogen( total) Wastewaters from urban waste water treatment plant Microwave-assisted oxidation of nitrogen-containing compounds to nitrate with an alkaline peroxydisulfate solution UV-Vis 0.21 mg L 1 Flow injection system chamber-like de- [434] bubbler for removal of the gaseous species formed during in-line oxidation nitrate reduction to nitrite Griess-Ilosvay reaction... 

The condensation of co-propargylic benzaldehydes with methyl sarcosi-nate or ethyl N-benzylglycinate followed by in sitn oxidation was also more efficient under microwave-assisted conditions for the synthesis of benzopyranopyrroles 80 [94]. Oxidation of the hexahydrochromeno[4,3-b]pyrrole cycloadducts could be facilitated by the addition of sulfur and further irradiation for 10 min at 130 °C in a one-pot process to give pyrroles 80 in 70-90% yield (Scheme 35). Although there was little difference between reactions carried out under microwave irradiation and those using classical conductive heating methodology, in terms of product yield, the microwave-assisted reactions had considerably shorter reaction times. Furthermore, a more convenient one-pot procedure, in which a mixture of the aldehyde, a-amino ester, sulfur and a minimal amount of xylene was irradiated for 15 min at 130 °C, provided the pyrrole product without any reduction in yield (90%) in a one-pot MCR. 

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