Invited Review. A Combinatorial Approach to the Development of Environmentally Benign Organic Chemical Preparations

Abstract

Enabling technologies and methodologies were established and combined to afford various environmentally benign processes for laboratory-scale organic synthesis and for the production of fine chemicals, intermediates and pharmaceuticals. The technologies comprised continuous and batch microwave reactors and catalytic membranes. The methodologies included solvent-free conditions, catalysed or uncatalysed processes, the use of aqueous media at high temperature and non-extractive techniques for product isolation. Applications included Hofmann eliminations, Willgerodt and Jacobs–Gould reactions, indole transformations, aldol condensation, Rupe and Meyer–Schuster rearrangements and C–C coupling reactions (including a tandem Heck coupling–dehydrogenation). New processes for catalytic etherification, uncatalysed hydrogen transfer and a one-step arylamidation were also developed. Typical products were N-(4-hydroxyphenyl)acetamide, carvacrol, a-phenylacetamide, cinnamaldehyde, cinnamyl alcohol, acetophenone, indole, 3-hydroxy-1,2-dimethyl-4-pyridone, di(2-phenylethyl) ether, di(cyclopropylmethyl) ether, 3-methylcyclopent-2-enone and a synthetic precursor of nalidixic acid.