Rate constants of Claisen rearrangement of allyl phenyl ether in suberitical water (272-306 degrees C) at 25.4 MPa were determined. The activation energy in this temperature range was evaluated to be 106 +/- 5 kJ mol(-1). To study the kinetics of reactions occurring in water at pressures up to 40 MPa and temperatures up to 400 degrees C, we developed a flow-through high-temperature and high-pressure NMR probe equipped with a mixing port above the RF detector. To suppress the large H-1 signal of H2O, the binomial sequence pulse technique was applied. (c) 2007 Elsevier B.V. All rights reserved.