Bis(acetonitrile) palladium (II) chloride (10 mol %) effects cyclization of δ-alkenyl oximes to nitrones which undergo in situ 1,3-dipolar cycloaddition reactions with suitable dipolarophiles to afford a range of complex isoxazolidine derived heterocycles in high yield (81–85%).
Palladium(II) chloride-catalysed cascade cyclisationâcycloaddition reactions of δ-alkenyl oximes occur regio- and facially-specifically in high yield via intermediate six-membered cyclic nitrones; preliminary studies of γ-alkenyl oximes show they are reluctant to cyclise; four potential synthetic variants of the cascade process are identified and examples of two of the classes are provided.
Oximes possessing γ-, δ-, or ω-alkenyl substituents are cyclised by N-bromosuccinimide or iodine to the corresponding cyclic nitrones or their dimeric H-bonded hydriodide salts in good yield; facially specific cycloaddition of these nitrones, and others derived by cyclisation of a δ,δ-bis(alkenyl) ketoxime or addition of acetaldoxime to cyclohexene, furnish isoxazolidines.
具有γ-、δ-或ω-烯基取代基的肟在 N-溴代琥珀酰亚胺或碘的作用下环化成相应的环状亚硝基膦或它们的二聚 H 键氢化物盐,收率很高;这些亚硝基膦以及其他通过环化δ,δ-双(烯基)酮肟或将乙醛肟加成到环己烯而得到的亚硝基膦的表面特异性环化反应生成异噁唑烷。
XY–ZH Systems as potential 1,3-dipoles. Part 51: Halogen-induced inter- and intra-molecular formation of nitrones from oximes and alkenes
作者:H Ali Dondas、Ronald Grigg、Maria Hadjisoteriou、Jasothara Markandu、Peter Kennewell、Mark Thornton-Pett
DOI:10.1016/s0040-4020(00)01084-x
日期:2001.2
Oximes possessing γ- and δ-alkenyl substituents are cyclised by N-bromo- or N-iodosuccinimide, iodine or ICl to the corresponding cyclicnitrones or their dimeric H-bonded hydroiodide salts in good yield; facially specific cycloaddition of these nitrones, and others derived by cyclisation of δ,δ-bis(alkenyl) ketoximes or by iodine induced addition of acetaldoxime to cyclohexene, furnish isoxazolidines