Synthesis and Fungicidal Activities of 4,5-Dihydro-7H-pyrano[3,4-c]isoxazole Derivatives.

4,5-Dihydro-7H-pyrano[3,4-c]isoxazoles (II and III) with an o-chlorophenyl or p-chlorophenyl group at C-7 were synthesized and the effect of substitution at C-3 of II and III on fungicidal activity was investigated in vivo. When the substituent at C-3 of II and III was CH2Br, CH=NOMe, CH=NOEt or CH=NO-allyl, the fungicidal effect was significant and selectively high on wheat leaf rust and barley powdery mildew at 250 ppm. Compound IId with the CH2Br substituent at C-7 showed high fungicidal activity against rice blast, providing more than 90% control of the disease at 2 ppm.