α,β-unsaturated oximes

摘要: Abstract At about 300° the title compounds yield fragments attributed to cyclisation isoxazolines and subsequent cycloreversion. Isoxazolines are formed at 200° can usually be isolated. they same products as oximes. Thus benzalacetophenone oxime gives 3,5-diphenylisoxazoline which then largely undergoes two distinct cycloreversions: (a) 1,3- cleavage (numbers refer isoxazoline bonds) yielding benzonitrile acetophenone (b) reductive 1,4- benzaldehyde 1-phenylethylimine hydrolysis products. By-products 2,4,6-triphenylpyridine, water ammonium benzoate. With α-methylchalcone 1,4-cleavage is suppressed with β-methylchalcone both modes of 5-methyl-3,5-diphenylisoxazole stable product. An analogue oxime, 2-methyl-1-phenyl-3-(2-thienyl)prop-2-ene-1-one an unisolatable hitherto unknown isoxazoline. Possible mechanisms for cycloreversions discussed believed a cycloreversion vinyl-nitrene.