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Synthesis of Spiroisoxazolines by 1,3-Dipolar Cycloaddition
Department of Organic Chemistry, Slovak Technical University, SK-812 37 Bratislava, Slovak Republic
Chemical Institute, PFUK, Mlynská dolina, SK-842 15 Bratislava, Slovak Republic
* Author to whom correspondence should be addressed.
Received: 31 August 1996; Accepted: 3 December 1996 / Published: 8 April 1997
Abstract: The cycloaddition of the chiral nitrile oxide 1 to 1-R-substituted 3,3-methylene-5,5-dimethyl-2-pyrrolidinones 2 (where R is H, n-butyl-, 1,1-dimethylethoxycarbonyl-, 1-methylethenyl- and acetyl-) proceeds regioselectively under the formation of spiroisoxazolines, namely 7-R-substituted-6-oxo-8,8-dimethyl-1-oxa-2,7-diazaspiro[4,4]non-2-enes 5 and 6. The asymmetric induction expected by the a-chiral centre of the nitrile oxide 1 was not very effective, diastereoisomers 5 and 6 were formed in an approximate 50:50 ratio. The stereoselectivity of the 1,3-dipolar cycloaddition of the arylnitrile oxide 7 with the chiral lactam 3 and the achiral lactone 4 are investigated. The attack of the 1,3-dipole occurred from the less hindered face of the dipolarophile 3 and 4, giving the major isomer 8 and 10, respectively.
Keywords: Lactams; lactones; stereoselectivity of 1; 3-dipolar cycloadditions; nitrile oxides
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Micuch, P.; Fisera, L.; Ondrus, V.; Ertl, P. Synthesis of Spiroisoxazolines by 1,3-Dipolar Cycloaddition. Molecules 1997, 2, 57-61.
Micuch P, Fisera L, Ondrus V, Ertl P. Synthesis of Spiroisoxazolines by 1,3-Dipolar Cycloaddition. Molecules. 1997; 2(3):57-61.
Micuch, Peter; Fisera, Lubor; Ondrus, Vladimír; Ertl, Peter. 1997. "Synthesis of Spiroisoxazolines by 1,3-Dipolar Cycloaddition." Molecules 2, no. 3: 57-61.