Diastereoselectivity and Reactivity in the Diels-Alder Reactions of α-Chloronitroso Ethers

Article abstract of DOI:10.1002/hlca.19860690522

The structure of the α-chloronitroso ether 1, obtained from the hydroximolactone 2 and tert-butyl hypochlorite (89percent), was established by X-ray crystallographic analysis.The <4+2> cycloadditions of 1 with dienes 3 and 8-11 led to the N-unsubstituted 3,6-dihydro-2H-1,2-oxazines 6 and 12-16 in high enantiomeric excess (Table 1).Due to the additional α-alkoxy group, the reactivity of 2 is much superior to the one of known α-chloronitrosoalkanes.The reactive conformation of 1 was deduced from the X-ray analysis as well as the high diastereoselectivity of the cycloadditions.The importance of the α-alkoxy group was evidenced from the similar reactivity of the racemic α-chloronitroso ethers 25-27 which were prepared from the hydroximo ethers 28-30 and tert-butyl hypochlorite.