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Haloacetylated enol ethers. 7 . Synthesis of 3‐aryl‐5‐trihalomethylisoxazoles and 3‐aryl‐5‐hydroxy‐5‐trihalomethyl‐4,5‐dihydroisoxazoles
Author(s) -
Martins Marcos A. P.,
Siqueira Geonir M.,
Bastos Giovani P.,
Bonacorso Helio G.,
Zanatta Nilo
Publication year - 1996
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570330612
Subject(s) - chemistry , aryl , hydroxylamine hydrochloride , hydrochloride , hydroxylamine , enol , yield (engineering) , organic chemistry , hydrochloric acid , sulfuric acid , medicinal chemistry , catalysis , alkyl , materials science , metallurgy
β‐Aryl‐β‐methoxyvinyl trihalomethyl ketones 1a‐g, 2a‐g [aryl = p ‐YC 6 H 4 where Y= H, Me, OMe, F, Cl, Br, NO 2 ] are cyclocondensed with hydroxylamine hydrochloride to afford the 3‐aryl‐5‐hydroxy‐5‐trihalomethyl‐4,5‐dihydroisoxazoles 3a‐g, 4a‐f in good yield. The dehydratation of compounds 3a‐g with concentrated sulfuric acid, led the corresponding 3‐aryl‐5‐trichloromethylisoxazoles 5a‐g . An alternative one‐pot procedure yields 3‐aryl‐5‐trihalomethylisoxazoles 5,6a‐g directly by cyclocondesation of 1,2a‐g with hydroxylamine hydrochloride in the presence of an excess of concentrated hydrochloric acid.