Starting with Microwave Chemistry

As a starting point for reaction optimization, Biotage offers a microwave reaction database (Emrys PathFinder) with ca. 4000 validated entries for microwave chemistry performed with Biotage single-mode instruments. 

The description of the association of heterocychc chemistry and microwave irradiation has also shown that performing microwave-assisted reactions should be considered with special attention. A few of these considerations can be applied generally for conducting microwave-assisted reactions and include the following (a) the ratio between the quantity of the material and the support (e.g., graphite) or the solvent is very important (b) for solid starting materials, the use of solid supports can offer operational, economical and environmental benefits over conventional methods. However, association of liquid/solid reactants on solid supports may lead to uncontrolled reactions which may result in worse results than the comparative conventional thermal reactions. In these cases, simple fusion of the products or addition of an appropriate solvent may lead to more convenient mixtures or solutions for microwave-assisted reactions. 

The first positive results in the synthesis of these heterocyclic compounds by MCR of aminoazoles, aldehydes, and barbituric acids were published in 2008 by Shi et al. [111]. They also used green chemistry methodology and carried out treatment of the starting materials in water under microwave irradiation. The temperature optimization procedure and search for the best catalytic system allowed selecting one equivalent of p-TSA and 140°C as optimum conditions for the synthesis. With application of the procedure elaborated 24 novel pyrazolopyr-idopyrimidines 76 were generated (Scheme 33). 

The real breakthrough of interstellar chemistry belongs to the post-war period and depended on the development of radioastronomy and microwave technologies that opened up quite new perspectives in celestial chemistry. However, since this modern phase only started in 1963 (with the detection of the radio signature of OH),... 

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