摘要
1,4-二烯是一类重要的烯烃化合物,其分子骨架广泛存在于药物和天然产物中.由于1,4-二烯分子在有机合成中具有重要作用,目前其合成方法已被广泛研究,包括1,3-二烯的氢烯基化、炔烃的氢烯丙基化、乙烯基和烯丙基试剂的交叉偶联等.然而,由于1,4-二烯的热力学稳定性,现有的合成方法主要倾向于生成E-立体选择性的产物,而Z-异构体的生成则相对困难.值得注意的是,通过同一组底物同时构建1,4-二烯的Z和E异构体的立体发散性合成策略鲜有报道.因此,发展新型催化体系,以同时构建1,4-二烯的Z和E异构体具有十分重要的意义和应用前景.本文报道了一种高效的可见光光致氧化还原/钴协同催化策略,该策略以联烯与炔烃为原料,通过调控反应溶剂即可实现立体发散性地构建Z,E-和E,E-1,4-二烯化合物.该反应在室温下,以2,4,5,6-四(9-咔唑基)-间苯二腈(4CzIPN)作为光敏剂,4,6-双(二苯基膦基)-10H-吩噁嗪为配体,H_(2)O和DIPEA作为氢源,实现了1,4-二烯的高效合成.值得一提的是,通过简单地调控溶剂可以直接控制产物的立体选择性,即以乙腈为溶剂时可得到Z,E-1,4-二烯产物,而使用2-MeTHF作为溶剂时,则得到E,E-1,4-二烯产物.此外,该反应对炔烃底物具有良好的兼容性,包括乙基、硅醚、羟基和环丙基等非对称的芳基烷基内炔,均能与联烯有效偶联,以较高收率得到目标产物.此外,芳基上带有各种富电子和缺电子基团的炔烃也能很好地参与反应.联烯底物研究结果表明,联烯上的酯基对反应效率有显著影响,具有较小酯取代基的联烯,如甲基和乙基,反应活性较低,相应的产物收率较低;而具有较大酯基的联烯,如异丙基、苄基和叔丁基,则能获得更高的产率.此外,当使用苯基、酸酐、二苯基氧化膦或磺酰基等其他官能团取代的联烯时,反应无法发生.通过氘代实验、荧光猝灭实验等一系列控制实验
1,4-Dienes are important scaffolds widely used in natural products and medicinal compounds.Herein,we report a highly efficient method for the straightforward synthesis of 1,4-dienes via regioand stereoselective reductive coupling of alkynes and allenes,catalyzed by visible-light photoredox cobalt.In contrast to the conventional E-alkene products,both(Z,E)-and(E,E)-1,4-dienes were synthesized with good regio-and stereoselectivities under mild conditions.In this photoredox reaction,Hünig’s base and water were utilized as hydrogen sources instead of the commonly used Hantzsch esters.The mechanistic and density functional theory studies indicate that the reaction undergoes protolysis of a cobaltacyclopentene intermediate and photocatalytic E→Z isomerization of(E,E)-1,4-dienes to(Z,E)-1,4-dienes via an energy transfer process.
作者
任行宇
刘佳俊
张士启
李彦霖
崔坤
李静
顾正洋
夏纪宝
Xing-Yu Ren;Jia-Jun Liu;Shi-Qi Zhang;Yan-Lin Li;Kun Cui;Jing Li;Zheng-Yang Gu;Ji-Bao Xia(School of Chemistry and Chemical Engineering&College of Textiles and Clothing,Yancheng Institute of Technology,Yancheng 224003,Jiangsu,China;State Key Laboratory for Oxo Synthesis and Selective Oxidation,Suzhou Research Institute of LICP,Lanzhou Institute of Chemical Physics(LICP),University of Chinese Academy of Sciences,Chinese Academy of Sciences,Lanzhou 730000,Gansu,China;College of Material Chemistry and Chemical Engineering,Key Laboratory of Organosilicon Chemistry and Material Technology,Ministry of Education,Hangzhou Normal University,Hangzhou 311121,Zhejiang,China)
基金
国家自然科学基金(22271296,22001226,22276161)
江苏省自然科学基金(BK20201193,BK20201473)
江苏省高等学校自然科学基金项目(20KJB150016)
兰州化学物理研究所重大计划项目(ZYFZFX-1)
江苏省青蓝工程.
关键词
1
4-二烯
钴催化
光氧化还原
还原偶联
炔烃
联烯
1,4-Dienes
Cobalt catalysis
Photoredox
Reductive coupling
Alkynes
Allenes
