Green chemistry methodologies

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). 

Green chemistry is an overarching approach that is applicable to all aspects of chemistry (Anastas, 2002). Green chemistry methodologies can be viewed through the framework of the Twelve Principles of Green Chemistry (Anastas, 1998) ... 

It is important that chemists develop new Green Chemistry options even on an incremental basis. While all elements of the lifecycle of a new chemical or process may not be environmentally benign, it is nonetheless important to improve those stages where improvements can be made. The next phase of an investigation can then focus on the elements of the lifecycle that are still in need of improvement. Even though a new Green Chemistry methodology does not solve at once every problem associated with the lifecycle of a particular chemical or process, the advances that it does make are nonetheless very important. 

In some cases special synthetic methodologies were applied to increase reactions yields or to satisfy green chemistry requirements. For example, Yao and co-authors [41] successfully carried out solvent-free three-component reaction of 5-ammotetrazole, aromatic aldehydes, and acetoacetic acid in the presence of inexpensive and commercially available sulfamic acid as catalyst. The yields of the MCRs were rather low but the whole procedure was facile, economic, and eco-friendly. 

With the valuable perspective afforded by the LCA methodology, let us return to our original question. What, then constitutes an appropriate solvent for green chemistry Fundamentally, it must be a solvent which allows the chemist to accomplish his or her task, but in an environmentally conscious manner. Chemists are expected to consider toxicity as part of the key elements affecting choice of solvents, so that they are minimally toxic to human health and the environment, and disposed of in ways that do not contribute to pollution (DeVito, 1996b). 

Miniaturization, one of basic trends in analytical chemistry, is playing a very important part in greening analytical methodologies.113-116 The main objectives of miniaturization are to... 

Anastas, T. 1999. Green chemistry and the role of analytical methodology development. Crit. Rev. Anal. Chem. 29 167-175. 

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