Microwaves in Organic Synthesis
The number of publications about the use of microwave heating in chemistry has grown almost exponentially in the last 20 years. Until recently, however, almost all the equipment available was only suitable for the synthesis of gram quantities of material. Process chemists and engineers are aware of the many advantages that the use of microwaves offers and are keenly waiting for large scale reactions to be feasible.
A recent presentation by Prof. Nicholas Leadbeater from the University of Connecticut, given at the 15th International Conference on Organic Process Research and Development in San Diego in January 2007, highlighted the progress that is being made in the scale up of microwave-promoted synthesis. The presentation looked at various different classes of reactions and the options available for scaling them up to multi-gram and even kilogram quantities. The options range from standard batch reactions to stop flow and continuous processing options.
Reactions can be carried out with or without solvent, in batch or continuous reactors, both of which have advantages and disadvantages. Six Case studies were presented:
- Palladium catalysed couplings (Suzuki and Heck)
- Open vessel chemistry (1,4-dihydropyridine synthesis and Beckmann rearrangements).
- Transesterification (biodiesel).
- Reactions using gaseous reagents (Pd catalysed carbonylation reactions)
- Esterification reactions.
- Continuous-flow chemistry (Beckmann rearrangement and Suzuki coupling).
As a result of the interest generated by the presentation Scientific Update in conjunction with the University of Connecticut are organising a 1-day training course "Microwave Heating as a Tool for Process Chemists". For more information, please visit our website.
Will Watson
