2,3-Dichloroquinoxaline has been reacted with several bifunctional compounds such as orthoaminophenol, orthoaminothiophenol, and orthophenylenediamine. These reactions gave a good yield of 1,4-diazabenzo[b]-phenoxazine derivatives by basecatalyzed condensation in aquous DMF. Furthermore, N-phosphoro derivatives of reaction products have been synthesized by the phosphorylation with 0,0-dialkyl phosphoro chloridated in anhydrous tetrahydrofuran. These N-phosphorylation gave a corresponding 10-dialkylphosphoro1,4-diazabenzo[b] phenoxazine derivatives. These new compounds are expected to exhibit pesticidal activity.