Although fire is now rarely used in synthetic chemistry, it was not until Robert Bunsen invented the burner in 1855 that the energy from this heat source could be applied to a reaction vessel in a focused manner. The Bunsen burner was later superseded by the isomantle, oil bath, or hot plate as a source for applying heat to a chemical reaction. In the past few years, heating and driving chemical reactions by microwave energy has been an increasingly popular theme in the scientific community. This nonclassical heating technique is slowly moving from a laboratory curiosity to an established technique that is heavily used in both academia and industry. The efficiency of "microwave flash heating" in dramatically reducing reaction times (from days and hours to minutes and seconds) is just one of the many advantages. This Review highlights recent applications of controlled microwave heating in modern organic synthesis, and discusses some of the underlying phenomena and issues involved.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/anie.200400655

Controlled microwave heating in modern organic synthesis.

Microwave assisted organic synthesis-a review

Microwave irradiation has been successfully applied in organic chemistry. Spectacular accelerations, higher yields under milder reaction conditions and higher product purities have all been reported. Indeed, a number of authors have described success in reactions that do not occur by conventional heating and even modifications of selectivity (chemo-, regio- and stereoselectivity). The effect of microwave irradiation in organic synthesis is a combination of thermal effects, arising from the heating rate, superheating or “hot spots” and the selective absorption of radiation by polar substances. Such phenomena are not usually accessible by classical heating and the existence of non-thermal effects of highly polarizing radiation—the “specific microwave effect”—is still a controversial topic. An overview of the thermal effects and the current state of non-thermal microwave effects is presented in this critical review along with a view on how these phenomena can be effectively used in organic synthesis.

Microwaves in organic synthesis. thermal and non-thermal microwave effects

Microwave assisted organic reactions

CuI‐Catalyzed Alkyne–Azide “Click” Cycloadditions from a Mechanistic and Synthetic Perspective

The use of microwave ovens for rapid organic synthesis

This work demonstrates that organic compounds can be synthesized up to 1240 times faster in sealed Teflon vessels in a microwave oven than by conventional (reflux) techniques. It is shown that all ...

The rapid synthesis of organic compounds in microwave ovens

This study shows that chemical reactions in polar solvents can be carried out rapidly and conveniently using microwave heating in sealed Teflon containers. Reactions of organic and or ganometallic compounds are reported, and rate enhancements of up to 1,240 times have been observed. The acceleration of reactions (compared to normal reflux conditions)oc curs because the increased pressure developed in the reaction vessels causes superheating of the solvent. The rate of absorption of microwave radiation is affected by the polarity and the volume of the reaction mixture. The heating rate is also influenced by the presence of ions in solution.The yields of relatively slow reactions can be increased by programming the power levels of the microwave oven. This technique allows the reactions to be carried out more safely and to be scaled up to some extent. Microwave heating results in considerable energy savings compared with conventional heating methods. The energy efficiency can be further increased by power pr...

R. N. Gedye

Papers

The use of microwave ovens for rapid organic synthesis

The rapid synthesis of organic compounds in microwave ovens

Microwaves in Organic and Organometallic Synthesis

Rate enhancement of organic reactions by microwaves at atmospheric pressure

Re-examination of Microwave-Induced Synthesis of Phthalimides