Transformation of substituted 2H-pyran-5-carboxylates into 3R*-vinyl-1,2R*-cyclopropanedicarboxylates

Substituted alkyl 2H-pyran-5-carboxylates, 1, have been condensed with methyl 2-(triphenylarsoranylidene) ethanoate, 14a, to form substituted 3-vinyl-1,2-cyclopropanedicarboxylates, 15, and, in a number of cases, 2,3-dihydro-3-vinyl-2,4-furandicarboxylates, 16. NMR experiments showed that for the majority of cyclopropane products formed, the cyclopropane ring hydrogen atoms have the trans configuration. This was validated by molecular orbital calculations. Biological screening tests revealed that these compounds showed some ectoparasiticidal activity.