The present disclosure provides a process for preparation of a compound of formula 1, or isomers or its derivatives thereof, which show a high herbicidal activity against wide variety of weeds. wherein R1 is a C3-C4 alkynyl group, a C1-C5 alkyl group, or a C3-C4 alkenyl group, and X is selected from the group consisting of F, Cl, Br, I or H atom.