「NR」Heck reaction——高效的烯烃衍生化方法
定义
钯催化烯烃的芳基化或烯基化被称为Heck反应
反应通式
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起源与发展
反应的一般特征
1)以单取代烯烃为原料制备双取代烯烃的最佳工艺条件;
2)烯烃上取代基的电子性质对反应结果的影响有限;它可以是供电子的,也可以是吸电子的,但通常缺电子的烯烃的产率更高;
3)反应条件允许烯烃组分上存在多种官能团:酯类、醚类、羧酸类、腈类、酚类、二烯类等均适合偶联,但烯丙醇类倾向于重排;
4)反应速率受烯烃取代程度的影响较大,取代程度越高的烯烃反应速度越慢;
5)非对称烯烃(如末端烯烃)的取代主要发生在取代最少的烯烃碳上;
6)芳基或乙烯基组分上的X基团的性质非常重要,其反应速率的变化顺序为:I > Br ~ OTf >> Cl;
7)R1组在大多数情况下是芳基,杂芳基,烯基,苄,而且很少是烷基(烷基需要β-位无氢原子),这些基团可以是给电子或吸电子基;
8)活性钯催化剂由合适的预催化剂(如Pd(OAc)2, Pd(PPh3)4)原位生成,反应通常在单齿或双齿膦配体和碱的存在下进行;
9)Heck反应对水不敏感,溶剂不需要彻底脱氧;
10)Heck反应是立体特异性的,钯复合物迁移插入烯烃和β-氢消除都是通过顺式立体化学进行
机理
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反应实例
1) Nickel-catalyzed intermolecular oxidative Heck arylation driven by transfer hydrogenation
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https://www.nature.com/articles/s41467-019-12949-1
2)Direct dehydrogenative alkyl Heck-couplings of vinylarenes with umpolung aldehydes catalyzed by nickel
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https://www.nature.com/articles/s41467-019-08631-1
3)A unique Pd-catalysed Heck arylation as a remote trigger for cyclopropane selective ring-opening
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https://www.nature.com/articles/ncomms14200
4)The Mizoroki–Heck Reaction
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https://onlinelibrary.wiley.com/doi/10.1002/9780470716076.ch1
5)Irradiation-Induced Heck Reaction of Unactivated Alkyl Halides at Room Temperature
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J. Am. Chem. Soc. 2017, 139, 50, 18307–18312
评述
参考
1. a)László Kürti, Barbara Czakó. StrategicApplications of Named Reactions in Organic Synthesis. b)Jie Jack Li. Name Reactions: A Collection ofDetailed Mechanisms and Synthetic Applications. c) 黄培强.有机人名反应、试剂与规则
2. https://www.organic-chemistry.org/namedreactions/ugi-reaction.shtm
3. a) https://pubs.acs.org/ b) https://onlinelibrary.wiley.com/
c) https://www.sciencedirect.com/ d) https://www.rsc.org/
e) https://www.thieme-connect.com/ f) http://www.sciencemag.org/
g) https://www.nature.com/natcatal/