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,1 and tetrahydrophospholo2,3-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.