Diastereoselectivity and Reactivity in theDiels-Alder Reactions of ?-Chloronitroso Ethers
作者:Helena Felber、G�nther Kresze、Roland Prewo、Andrea Vasella
DOI:10.1002/hlca.19860690522
日期:1986.7.30
hydroximolactone 2 and tert-butyl hypochlorite (89%), was established by X-ray crystallographic analysis. The [4 + 2] cycloadditions of 1 with the 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
通过X射线晶体学分析,确定了由氢氧内酯2和次氯酸叔丁酯(89%)获得的α-氯亚硝基醚1的结构。在[4 + 2]环加成的1与二烯3和8 - 11导致Ñ -未被取代的3,6-二氢-2- ħ -1,2-恶嗪6和12 - 16高对映体过量(表1) 。由于额外的α-烷氧基,2的反应性远远优于已知的α-氯亚硝基链烷烃之一。的反应构象从X射线分析以及环加成的高非对映选择性推论出1。α-烷氧基的重要性由外消旋α-chloronitroso的类似的反应性证实醚25 - 27,其从该hydroximo制备醚28 - 30和叔丁基次氯酸盐。