%0 Journal Article
%T Synthesis of Spiroisoxazolines by 1,3-Dipolar Cycloaddition
%A Peter Micuch
%A Lubor Fisera
%A Vladim¨ªr Ondrus
%A Peter Ertl
%J Molecules
%D 1997
%I MDPI AG
%R 10.3390/20300057
%X 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.
%K Lactams
%K lactones
%K stereoselectivity of 1
%K 3-dipolar cycloadditions
%K nitrile oxides
%U http://www.mdpi.com/1420-3049/2/3/57