3-phenyl-4-acyl-5-isoxazolones

The next category of f)-diketones are 4-acyl-l-phenyl-3-methyl-5-pyrazolones (see Eigure 2.5) and their analogs of 3-phenyl-4-acyl-5-isoxazolones (see Eigure 2.6). The latter type of P-diketones have stronger acidities (lower pA a values) than the former, and have recently been smdied as promising light conversion molecular devices [46-51]. 

Figure 2.6 Molecular structures of 3-phenyl-4-acyl-5-isoxazolones.

Figure 2.20 Asymmetric unit of complexes Tb(L )3(H20)2, thermal ellipsoids drawn with 30% probability and hydrogen atoms omitted for clarity [51a], (Reproduced from S. Iju, M.L.P. Reddy, A.H. Cowley and K.V. Vasudevan, 3-Phenyl-4-acyl-5-isoxazolonate complex of Tb + doped into poly-P-hydroxybutyrate matrix as a promising light-conversion molecular device, Journal of Materials Chemistry, 19, 5179-5187, 2009, by permission of the Royal Society of Chemistry.)...

Hydrazino-5,6-diphenyl-l,2,4-triazine (289) reacts with 4-benzylidene-2-phenyl-5(4//)-oxazo-lones (290) and 4-benzylidene-3-methyl-5(4//)-isoxazolones (291) in toluene to products (292), (293) substituted in the hydrazino group, the first by acylation by the oxazolone, the second by arylraethylidene group transfer (Scheme 53) <88JHC1813>. 

Photolysis of 3-phenyl-5(4H)-isoxazolone yields 2,5-diphenylpyrazine in 67% yield. Singlet excited isoxazol-5-one (224) undergoes both decarbonylation and decarboxylation to carbene intermediates, both of which are captured by alcohol or amine solvents. With triplet sensitisers an oxaziridine intermediate reacts with the solvent. N-Acylisoxazol-5-ones decarboxylate to yield singlet carbenes (225) which cyclise at the acyl oxygen to yield the isoxazoles (227), and the isothiazoles (228) are obtained via thioacyl carbenes (226) from N-thioacylisazol-5-ones. " The isolation of (229) as the main product from irradiation of benzophenone/N,N-dimethylaniline in the presence of the non-polymerising... 

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