Supercritical water (scH(2)O) is utilized for organic synthesis as an acid- or a base-catalyst as well as a useful replacement for organic solvents. There have been few works on the use of scH(2)O for acid- or base-catalyzed organic synthesis, because the ion product of scH(2)O is much lower than liquid water under certain conditions. Our recent studies by in situ Raman and IR spectroscopic measurements were allowed to expect the occurrence of acid- or base-catalysis of scH(2)O. Contrary to the conventional wisdom that acid- or base-catalyzed reactions will not take place in scH(2)O, these results indicated the possibilities of scH(2)O participating in Lewis acid- or base-catalysis, besides the Brønsted acid-base function. In this paper, we thus demonstrate that the new-generation syntheses of lactam, arylated olefin, and monoterpene alcohols can be successfully created in scH(2)O.