APPLICATIONS OF HIGH-TEMPERATURE AQUEOUS-MEDIA FOR SYNTHETIC ORGANIC-REACTIONS

Preparative organic synthesis was investigated in aqueous media at tem peratures up to 300 degrees C. Experiments were conducted with a recen tly disclosed pressurized microwave batch reactor (MBR) or in conventi onally heated autoclaves. Thirty-six examples are presented. Among the se, methods were developed for a Fischer synthesis, an intramolecular aldol condensation that was scaled up, decarboxylation of indole-2-car boxylic acid, Rupe rearrangement of 1-ethynyl-1-cyclohexanol, isomeriz ation of carvone to carvacrol, and conversion of phenylacetylene to ac etophenone. The applicability of high-temperature water was also demon strated for biomimetic processes important in food, flavor, and aroma chemistry and for tandem reactions such as formation of 2-methyl-2,3-d ihydrobenzofuran from allyl phenyl ether. When addition of acid or bas e was necessary, less agent was usually required for high-temperature processes than for those at and below boiling, and the reactions often proceeded more selectively. In some instances the requirement was ord ers of magnitude lower, with obvious consequences for safe, economic p rocessing and for lowering costs of effluent disposal. The diversity o f reactions indicates that high-temperature aqueous media could play a n increasingly important role in the development of new preparative pr ocesses.