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Haloacetylated enol ethers. 5 [5]. Heterocyclic ring closure reactions of β‐alkoxyvinyl dichloromethyl ketones with hydroxylamine
Author(s) -
Martins Marcos A. P.,
Zoch Ala.,
Flores Alex F. C.,
Clar Günter,
Zanatta Nilo,
Bonacorso Helio G.
Publication year - 1995
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.5570320307
Subject(s) - chemistry , enol , hydroxylamine , bicyclic molecule , sulfuric acid , ring (chemistry) , yield (engineering) , medicinal chemistry , pyridine , ketone , organic chemistry , hydroxylamine hydrochloride , oxime , catalysis , materials science , metallurgy
The β‐alkoxyvinyl dichloromethyl ketones 1a‐d are cyclocondensed with hydroxylamine hydrochloride in pyridine to afford the 5‐hydroxy‐5‐dichloromethyl‐4,5‐dihydroisoxazoles 2a‐d in good yield. The cyclo‐condensation of compound 1c gave, together with 2c , 3‐cyano‐2‐hydroxy‐2‐dichloromethyltetrahydrofuran 5c. The dehydratation of compounds 2a,b , derived from acyclic enol ethers, with concentrated sulfuric acid at 30°, led the corresponding 5‐dichloromethylisoxazoles 3a,b. The dehydratation of compounds 2c,d , derived from cyclic enol ethers, with concentrated sulfuric acid at 30°, led the bicyclic 4,5‐dihydroisoxazoles 4c,d , and at 55°, a competitive rearrangement reaction gives the 3‐cyano‐2‐hydroxy‐2‐dichloromethyl‐2 H ‐pyran 5d.