Synthesis and X-ray study of hexahydro- and tetrahydrophospholo[2,3-d]isoxazoles, a new class of heterocycles of potential fungicidal activity

Hexahydro-, 5b-1 and 6a,f,l and tetrahydropho spholo[2,3-d]isoxazoles 8, 9 and 10 were synthesized by 1,3-dipolar cycloaddition of nitrones 3b-1 and benzonitrile oxide (4) to 2,3-dihydro-1-phenyl-1H-phosphole 1-oxide (1) and 2,3-dihydro-1-ethoxy-1H-phosphole 1-oxide (2). The structural assignment to the compounds was confirmed by an X-ray study of two compounds of the series 5a and 5m. The compounds show a good activity as fungicides against Plasmopara viticola on vines and against Botrytis cinerea on apples. Compounds 5a-d showed weak to moderate activity as herbicides.