Translating Conventionally Heated Methods

Microwave heating is often applied to already known conventional thermal reactions in order to accelerate the reaction and therefore to reduce the overall process time. When developing completely new reactions, the initial experiments should preferably be performed only on a small scale applying moderately enhanced temperatures to avoid exceeding the operational limits of the instrument (temperature, pressure). Thus, single-mode reactors are highly applicable for method development and reaction optimization. 

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As an example, in the solid-phase synthesis of di-substituted, tri-substituted, and fully-substituted pyrazolidine-3,5-diones microwave heating proved valuable in a key acylation step. Conditions were first developed for performing the reaction on a solution-phase analog using conventional methods. However, use of controlled microwave heating (90 °C for 1 h) gave superior results. This translated well from solution phase to solid phase. A small library of 25 members was prepared in order to demonstrate the versatility of the chemistry. 

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