MORE Chemistry for Less Pollution: Applications for Process Development

Abstract

Microwave-assisted rapid organic reactions constitute an emerging technology that could make industrially important organic syntheses more eco-friendly than conventional reactions. In our laboratory Microwave-Induced Organic Reaction Enhancement (MORE) chemistry techniques have been developed that are safe since all reactions are conducted in open systems to avoid any chance of explosions that have been observed in sealed systems. MORE chemistry can be conducted without an added solvent if one or more of the reactants is a liquid that absorbs microwaves efficiently. When it is necessary to add a dipolar solvent for transferring microwave energy to the reactants, it is adequate to add just enough solvent to form a slurry at room temperature. The growing concern about the effect of organic solvents and chemical wastes on the environment is attracting attention to non-traditional synthetic approaches that might 'reduce pollution at the source'. In this context MORE chemistry techniques are potentially valuable as they reduce the need for organic solvents and also increase 'atom economy' by improving product selectivity and chemical yield.

Studies with Enamines: Route to Aminoazolopyrimidines and Arylazoazolopyrimidines

“…- 1 [1,2,4]triazolo [1,5-a]pyrimidin-7-amine (12) Method A. A mixture of 11b (0.01 mol, 0.98 g) and enaminonitrile 1a (0.01 mol, 1.36 g) in pyridine (25 mL) was refluxed for 3 h. The reaction mixture was left to cool to room temperature, and the solid formed was collected by filtration and crystallized from ethanol to afford 12 (yield 60 %).…”

“…The major benefits of performing reactions under microwave conditions are significant rate enhancements and higher product yields as compared to reactions which are run under conventional heating. Key advantages of modern, scientific microwave apparatus are their ability to control reaction conditions precisely by monitoring temperature/pressure and reaction times and ease of isolation of the products after work-up [11,12].…”

Account of microwave irradiation for accelerating organic reactions

“…The corresponding chromanones 9 have been obtained by the reaction of 3-hydroxy phenolic derivatives with N-cinnamoylazoles 10 . Coumarins were synthesized by condensation of salicylaldehydes with malonic acid, derivatives of ethyl acetate or hydrazides and by Knoevenagel condensation of benzaldehydes or acetophenones with Meldrum's acid; reactions did not take place in the absence of MWI or catalyst 11,12 . Diels-Alder reaction of (E)-and (Z)-3-styrylchromones with N-methyl and N-phenyl maleimide afforded the respective exo-and endo-cycloadducts stereoselectivly.…”

Microwave assisted synthesis of 2-amino-6-methoxy-4H-benzo[h]chromene derivatives

“…Microwave heating has been known for accelerating the organic reactions [51][52][53]. Cyclocondensation reactions in "dry media" leading to heterocyclic systems have been performed under microwave irradiation [54][55][56][57][58][59][60].…”