cycloaddition of nitrile imines with 3-alkenyl-oxindoles was catalyzed by a new chiral Mg(ClO4)2 complex of an N,N′-dioxide ligand. The reaction is so far the sole catalytic synthesis of spiro-pyrazoline-oxindole derivatives. A wide variety of substrates were explored to obtain good yields (up to 98%) and excellent enantioselectivities (up to 99%). This cycloaddition expands the scope of propargyl anion type 1
Certain benzoyl chloride phenylhydrazones have been found to be active against insects and mites, and they have also been found to be effective, broad-spectrum anthelmintics for suppressing parasitic worms in animals, particularly sheep. The benzoyl ring and the phenylhydrazone ring can be substituted with a halogen atom, a nitro group, or an alkyl group of from 1 to 6 carbon atoms, inclusive. A new class of pentahalobenzoyl chloride phenylhydrazones is described, particularly pentafluorobenzoyl chloride phenylhydrazones. The compounds are prepared by reacting a benzoic acid phenylhydrazide with phosphorus pentachloride to obtain a benzoyl chloride (dichlorophosphinyl)phenylhydrazone that is reacted with phenol to produce the desired benzoyl chloride phenylhydrazones. Certain of the compounds can be prepared by direct chlorination of a benzaldehyde phenylhydrazone. Methods of using the new compounds and new anthelmintic formulations are described. The new compound p-toluoyl chloride phenylhydrazone is effective against worms at rates at least as low as 100 mg./kg. of body weight in sheep.
[3 + 2] cycloaddition of para-quinone methides with nitrile imines under mild conditions has been achieved. The corresponding spiro-pyrazoline-cyclohexadienone products were constructed in good to excellent yields (up to 97% yield) with high regioselectivity. This straightforward protocol exhibits good functional group tolerance and scalability and provides the spiro-pyrazoline-cyclohexadienones.
The double 1,3-dipolar cycloaddition of allenoates with nitrilimines has been achieved under mild reaction conditions, affording a variety of spirobidihydropyrazoles in moderate to excellent yields with excellent diastereoselectivities. The reaction diastereoselectively constructs double dihydropyrazole moieties and two chiral centers including a spiro carbon center.
stereoconvergent 1,3-dipolar cycloaddition of nitrileoxides and nitrile imines with E/Z isomeric mixture of electron-deficient olefins is reported, delivering isoxazolines and pyrazolines bearing two vicinal stereogenic tertiary and trifluoromethylated quaternary carbon centers with perfect regio- and diastereoselectivities. The possibility of concerted cycloaddition/epimerization sequence under basic