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Photochemistry of 4- and 5- phenyl substituted isoxazoles

✍ Scribed by James W. Pavlik; Heather S T. Martin; Karen A. Lambert; Jennifer A. Lowell; Vikki M. Tsefrikas; Cheryl K. Eddins; Naod Kebede

Publisher
Journal of Heterocyclic Chemistry
Year
2005
Tongue
English
Weight
151 KB
Volume
42
Category
Article
ISSN
0022-152X

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✦ Synopsis

5-Phenylisoxazole (4) and 4-phenylisoxazole (22) underwent phototransposition to 5-phenyloxazole (5) and 4-phenyloxazole (24) respectively. Labeling with deuterium or methyl confirmed that these phototranspositions occurred via the P 4 pathway which involves only interchange of the N2 and C3 ring position. Thus, 4-deuterio-5-phenylisoxazole (4-4d), 4-methyl-5-phenylisoxazole (10), and 5-methyl-4-phenylisoxazole (23) phototransposed to 4-deuterio-5-phenyloxazole (5-4d), 4-methyl-5-phenyloxazole (11), and 5-methyl-4-phenyloxazole (25) respectively. In addition to phototransposition, isoxazoles 4, 10, and 23 also underwent photo-ring cleavage to yield benzoylacetonitrile (9), Ξ±-benzoylpropionitrile (15), and aceto-Ξ±-phenylacetonitrile ( 26) respectively. Irradiation of 5-phenyl-3-(trifluoromethyl)isoxazole ( 16) in acetonitrile led to 5-phenyl-2-(trifluoromethyl)oxazole ( 17), the P 4 phototransposition product. Irradiation of 16 in methanol led to a substantial decrease in the yield of 17 and to the formation of a mixture of (E) and (Z)-2-methoxy-2-(trifluoromethyl)-3-benzoylaziridines 18a and 18b.

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