Heck reactions in hydrothermal, sub-critical water: water density as an important reaction variable

Heck coupling reactions of iodobenzene and cyclohexene in sub-critical wate r illustrate the importance of water density as a reaction variable. Alteri ng the water density from 0.03 to 0.84 g/mL and the reaction pressure from 30 to greater than 213 bar at 225 degreesC changed both product and isomer yields. The multiple physical effects of water density were also explored b y the addition of ionic salts. Changing the isothermal state of the liquid water, measurably altered coupling reaction pathways suggesting that chang es in solvent-solute interactions can influence transition states favoring some configurations and disfavoring others. (C) 2001 Elsevier Science Ltd. All rights reserved.