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Catalytic transfer hydrogenation has been conducted under microwave irradiation in open vessels using high-boiling solvents such as ethylene glycol (bp 198 °C) as the microwave energy transfer agent. Reduction of double bonds and hydrogenolysis of several functional groups were carried out safely and rapidly (3-5 min) at about 110-130 °C with 10% Pd/C as an efficient catalyst and ammonium formate as the hydrogen donor. Diverse types of β-lactam synthons were prepared by the reduction of ring substituents containing alkene and alkylidene groups or conjugated unsaturated esters. Cleavage of the β-lactam ring by hydrogenolysis of the N-C 4 bond of 4-aryl-2-azetidinones was a facile reaction with 10% Pd/C as the catalyst; but no ring scission occurred when Raney nickel catalyst was employed. Dehalogenation of aromatic compounds was also successful with ammonium formate and Pd/C catalyst. Hydrogenolysis of phenylhydrazone of methyl benzoylformate gave the methyl ester of phenylglycine in excellent yield. The techniques described here for microwave assisted hydrogenation are safe, rapid, and efficient and are suitable for research investigation as well as for undergraduate and high school laboratory exercises.

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Microwave-assisted rapid organic reactions constitute an emerging technology that could make industrially important organic syntheses more eco-friendly than conventional reactions. In our laboratory Microwave-Induced Organic Reaction Enhancement (MORE) chemistry techniques have been developed that are safe since all reactions are conducted in open systems to avoid any chance of explosions that have been observed in sealed systems. MORE chemistry can be conducted without an added solvent if one or more of the reactants is a liquid that absorbs microwaves efficiently. When it is necessary to add a dipolar solvent for transferring microwave energy to the reactants, it is adequate to add just enough solvent to form a slurry at room temperature. The growing concern about the effect of organic solvents and chemical wastes on the environment is attracting attention to non-traditional synthetic approaches that might 'reduce pollution at the source'. In this context MORE chemistry techniques are potentially valuable as they reduce the need for organic solvents and also increase 'atom economy' by improving product selectivity and chemical yield.

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