We have previously reported the insecticidal activity of some 4H-1, 3, 2- benzoxazaphosphorines (BOPs) with no substituent on the benzene ring. 1) This paper deals with the insecticidal activity of 31 kinds of BOP-2-thiones (V), which were synthesized to examine the substituent effects at the 2, 3, 6, and 8 positions of BOP (Fig. 1). Schiff bases (II) prepared from the corresponding salicyl aldehydes (I) and amines2) were reduced by ...