Method for producing monosulfoxide derivative

A method for producing a compound of formula (B):

• wherein, R1 is a C1-C4 alkyl group, a C2-C4 alkenyl group, a C2-C4 alkynyl group, a C1-C4 haloalkyl group, a C2-C4 haloalkenyl group, or a C2-C4 haloalkynyl group;
• R2 and R3 are each independently a hydrogen atom, a halogen atom, a C1-C4 alkyl group, a C2-C4 alkenyl group, a C2-C4 alkynyl group, a C1-C4 haloalkyl group, a C2-C4 haloalkenyl group, a C2-C4 haloalkynyl group, a C1-C4 alkoxy group, or a C1-C4 haloalkoxy group;
• and n is 5 or 6,
• comprising an oxidation step of reacting a compound of formula (A):
• wherein, R1, R2, R3, and n are as defined above,
• with a hydrogen peroxide in the presence of a metal catalyst, wherein the metal catalyst is one or more catalysts selected from the group consisting of vanadium catalyst, molybdenum catalyst, and titanium catalyst, and
• wherein ligands and benzoic derivatives are not used in the oxidation step.