The facile synthesis of 6-methylene-6,7-dihydro-4H-selenazolo [2,3,-c] [1,2,4] triazin-4-one (3) has been performed by the catalytic action of Pd (II) salt on 3-propargylseleno-1,2,4-triazine (2). Under basic condition compound (3) was isomerized to 3, 6-dimethyl-4H-selenazolo [2, 3-c] [1,2,4] triazin-4-one (5).