5-Amino-4-benzoyl-isoxazole

The standard procedure including treatment with bromoacetyl bromide and then with hexamethylenetetramine was used to prepare isoxazolo[5,4-e]1.4-diazepin-7-one 59 from 5-amino-4-benzoyl-isoxazole (74HCA1934) (Scheme 25). 

Isoxazole-oxazole photoisomerization was studied by irradiation of matrix-isolated 3,5-dimethylisoxazole (18) at 222 nm. 2-Acetyl-3-methyl-2H-azirine (20) was obtained, likely through an acetyl vinyl nitrene intermediate 19 as primary photoproduct, while upon longer time UV irradiation, two additional photoproducts were identified as acetyl nitrile ylide 21 and 2,5-dimethyloxazole (22) (13JOC10657). Analogously, 3,5-diphenylisoxazole and 2-benzoyl-3-phenyl-2f/-azirine behaved as precursors to triplet vinyl nitrene (of type 19) through laser flash photolysis (13JOC11349). Reductive heterocycle—heterocycle transformations of (2-nitrophenyl)isoxazole precursors, such as 23 and 26, afforded 4-amino quinolines of type 24, quinolin-4(lfJ)-ones 25, and 3-acylindoles 27. Che-moselective heterocyclizations were observed from 3,4-,4,5-, and 3,4-bis(2-nitrophenyl)isoxazoles (13OL2062). 

---