Microwave assisted organic synthesis-a review

Microwave assisted organic reactions

Industrial use of microwave radiation as an alternative to conventional thermal heating has generated interest recently mainly because of the drastic reduction in the processing time. In spite of its wide application, its chemical mechanism of interaction with materials has not been well understood. The current debate on the alternative use of microwave radiation to conventional thermal heating is on the involvement of a “microwave specific effect” other than the well accepted dielectric heating. There are reports of various reactions which show similar kinetics under both microwave and thermal methods at similar temperatures suggesting simple dielectric heating of materials by microwaves. There are also reports which show a clear reaction rate enhancement under microwave radiation compared to the thermal method under similar reaction conditions and temperatures indicating a “microwave specific effect” other than the simple dielectric heating of materials. This paper will discuss the above conflicting results reported in the literature.

Thermal and non-thermal interaction of microwave radiation with materials

Microwave-Promoted Palladium-Catalyzed Coupling Reactions

In situ generation of molecular hydrogen by addition of triethylsilane to palladium-charcoal catalyst results in rapid and efficient reduction of multiple bonds, azides, imines, and nitro groups, as well as benzyl group and allyl group deprotection under mild, neutral conditions.

Pd−C-Induced Catalytic Transfer Hydrogenation with Triethylsilane

Microwave-induced organic reaction enhancement chemistry. 2. Simplified techniques

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−C4 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 te

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Khaled J. Barakat

Papers

Microwave-induced organic reaction enhancement chemistry. 2. Simplified techniques

Microwave-assisted rapid and simplified hydrogenation

Microwave-induced organic reaction enhancement chemistry.4 convenient synthesis of enantiopure α-hydroxy-β-lactams1

Simplified Rapid Hydrogenation Under Microwave Irradiation: Selective Transformations of β-Lactams1

Microwave‐Induced Organic Reaction Enhancement (MORE) Chemistry. Part 13. Microwave‐Assisted Rapid and Simplified Hydrogenation.