Reaction methods microwave-assisted organic chemistry

For combinatorial chemistry to deliver on its promise, general methods need to be discovered to accelerate soHd-phase reactions to the point at which they are equivalent in rate to, or faster than, homogeneous reactions. Microwave-assisted organic synthesis has had considerable success in achieving this goal. Since 1990, many organic transformations have been accelerated by subjecting them to microwave (MW) irradiation. In most cases reaction times of hours to days have been reduced to seconds to minutes. 

One of the cornerstones of combinatorial synthesis has been the development of solid-phase organic synthesis (SPOS) based on the original Merrifield method for peptide preparation [19]. Because transformations on insoluble polymer supports should enable chemical reactions to be driven to completion and enable simple product purification by filtration, combinatorial chemistry has been primarily performed by SPOS [19-23], Nonetheless, solid-phase synthesis has several shortcomings, because of the nature of heterogeneous reaction conditions. Nonlinear kinetic behavior, slow reaction, solvation problems, and degradation of the polymer support, because of the long reactions, are some of the problems typically experienced in SPOS. It is, therefore, not surprising that the first applications of microwave-assisted solid-phase synthesis were reported as early 1992 [24],... 

According to Scheme 2.1 the principles of green chemistry can be condensed to the word productively [16]. Two main goals are to eliminate or minimize the use of volatile organic solvents in modern syntheses and to reduce energy inputs. Development of new synthetic solvent-free methods with microwave assistance is an important topic of research with growing popularity, because solvent-free reactions reduce solvents usage, simplify synthesis and separation procedures, prevent waste, and avoid the hazards and toxicity associated with the use of solvents [135]. 

---