To produce an isochroman-3-one at a low cost on an industrial scale by reacting a specific compound with carbon monoxide under a specified pressure in the presence of an ionic halide and a palladium catalyst in a specific solvent.
(A) A 1,3-dihydroisobenzofuran represented by formula I (R1 to R4 are each H, HO2CCH=CH, a 1-18C alkyl or the like) is reacted with (B) carbon monoxide in the presence of (C) an ionic halide in an amount of 1-50 mol.% based on the component A and (D) a palladium catalyst in an amount of 0.0001-1% based on the component A in (E) a dipolar aprotic solvent (e.g. N-methylpyrrolidone) under 0.1-20 MPa pressure of the component B to produce an isochroman-3-one represented by formula II. An alkali metal, ammonium or a phosphonium halide is preferred as the component C. A metallic palladium, etc., supported on a carrier are preferred as the component D.
DECKER DANIEL DR
GROSS PETER
