5-Acetyl-3-methylisoxazole

Acetonitrile oxide regioselectively reacts with dialkylaminobutenones to form 5-acetyl-3-methylisoxazole (322) and a small amount of 4-acetyl-3-methyl-isoxazole (323) (92SC2902). 

The irradiation of 3-phenyl-4-acetyl-5-methylisoxazole (49) gave the isomeric oxazole (50) (Scheme 22) (75JA6484 76HCA2074). The reaction can involve the formation of the biradical intermediate starting from the triplet state, in agreement... 

The reactions of 2-substituted 6-methyl-4/7-l,3-oxazin-4-ones 98 with isoxazole ketones 99 in the presence of potassium / -rt-butoxide furnished 3-acetyl-5-(3-methylisoxazol-5-yl)-2-pyridones 101 in good to excellent yields (Scheme 14). The formation of 2-pyridones 101 presumably proceeds via nucleophilic addition of the methylene carbon of 99 to the carbon atom at position 2 of the l,3-oxazin-4-ones 98, followed by ring opening to give the acetoacetyl intermediates 100, which are transformed into 101 by intramolecular aldol condensation <2005H(66)299>. 

Pyrazole and isothiazole " undergo straightforward nitration, at C-4, but the less reactive isoxazole nitrates in negligible yield 3-methylisoxazole, however, has sufficient extra reactivity that it can be satisfactorily nitrated, at C-4. With acetyl nitrate or dinitrogen tetraoxide/ozone, 1-nitropyrazole is formed but this can be rearranged to 4-nitropyrazole in acid at low temperature. ... 

Amino-5-methylisoxazole 21 reacted with chloro acetyl chloride in dry benzene and in the presence of triethylamine to afford N-l-(5-methyl-3-isoxazolyl)-2-chloroacetamide 22. Compound 22 reacted with resorcinol and anhydrous K2CO3 in Dimethyl formamide (DMF) at ambient temperature to produce 2-(3-hydroxyphenol)-N-(5-methyl-3-isoxazolyl)acet-amides 23. Then 23 reacted with a /1-ketoester in the presence of catalytic amount of CoPy2Cl2 to furnish isoxazolylcoumarins 24 in high to excellent yields (80-95%) (Scheme 13) (101JC532). 

Acetyl-5-methylisoxazole oxime fused 15 min. with Gu-powder 3-acetonyl-... 

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