Reactions of chromones with dilithiooximes proceed via nucleophilic 1,2-addition to give, on acidification, 4H-chromene-4-spiro-5′-isoxazoline derivatives in high yields. On treatment with concentrated H2SO4 the isoxazoline ring of this novel spiroannulated heterocyclic system opens to give α,β-unsaturated oximes, which undergo nitrosation, bromination, and the Beckmann rearrangement to the corresponding
色酮与二
硫代
肟的反应通过亲核的1,2-加成反应进行,酸化后可高产率生成4 H-色
烯-4-螺5-5'-
异恶唑啉衍
生物。在用浓H 2 SO 4处理时,该新型螺环杂环体系的
异恶唑啉环打开,得到α,β-不饱和
肟,将其亚硝化,
溴化和贝克曼重排,分别形成相应的螺
异恶唑啉和α,β-不饱和
酰胺。 。后者可以直接通过4 H-色
烯基-4-spiro-5'-
异恶唑啉的贝克曼重排获得。