Direct Access to 4,5<i>-</i>Disubstituted [2.2]Paracyclophanes by Selective<i>ortho</i>-Halogenation with Pd-Catalyzed C-H Activation
作者:Joshua J. P. Kramer、Ceylan Yildiz、Martin Nieger、Stefan Bräse
DOI:10.1002/ejoc.201301723
日期:2014.2
A palladium-catalyzed protocol for the halogenation of [2.2]paracyclophanes by C–H activation is described, and ortho selectivity is achieved with an O-methyloxime directing group. Bromination and iodination of the sterically demanding [2.2]paracyclophane proceed in good yields with inexpensive and readily available N-halosuccinimides. Deprotection of the O-methyloximes yields ortho-halogenated aldehydes
描述了通过 C-H 活化卤化 [2.2] 对环芳烃的钯催化方案,并通过 O-甲基肟导向基团实现了邻位选择性。使用廉价且容易获得的 N-卤代琥珀酰亚胺,空间要求较高的 [2.2] 对环芳烷的溴化和碘化以良好的收率进行。O-甲基肟的脱保护产生作为有吸引力的中间体的邻卤化醛,用于模块化合成 4,5-二取代 [2.2] 对环芳烷。该协议的合成价值通过甲醛和卤素位点的示例性转换得到证明。此外,早期拆分和随后的溴化/脱保护提供了对映纯形式的溴化醛。