RuH 2 (PPh 3 ) 4 -catalyzed reaction of nitriles with terminal alkynes proceeds highly efficiently under neutral conditions to give the corresponding Michael adducts. Furthermore, 1,3-dicarbonyl compounds react with terminal alkynes at the α-position to afford the exo-methylene compounds with high regioselectivity under neutral conditions. The regioselectivity depends upon the change of substrates
RuH 2 (PPh 3 ) 4 催化的腈与末端炔烃的反应在中性条件下高效进行,得到相应的迈克尔加合物。此外,1,3-二羰基化合物在α-位与末端炔烃反应,在中性条件下提供具有高区域选择性的外亚甲基化合物。区域选择性取决于底物的变化。提出了精确的机制。
Anti-Selective Epoxidation of Methyl α-Methylene-β-<i>tert</i>-butyldimethylsilyloxycarboxylate Esters. Evidence for Stereospecific Oxygen Atom Transfer in a Nucleophilic Epoxidation Process
作者:Jakub Švenda、Andrew G. Myers
DOI:10.1021/ol900665a
日期:2009.6.4
Methyl α-methylene-β-tert-butyldimethylsilyloxycarboxylate esters are found to undergo diastereoselective epoxidation in the presence of potassium tert-butoxide−tert-butyl hydroperoxide to form anti products. In an effort to better understand mechanistic details of the transformation and the basis of diastereoselectivities observed, we studied the epoxidation of substrates with α-methylene groups containing
Cobalt-promoted B–H and C–H activation in the three-component reactions of 16-electron cobalt carboranedithiolate, alkyne and bronsted acids
作者:Rui Zhang、Lin Zhu、Zhenzhong Lu、Hong Yan
DOI:10.1016/j.jorganchem.2015.06.013
日期:2015.12
isolated where L1–L3 loses one proton to provide 3 electrons to metal and alkyne is reduced to olefin. If L4 and L5 are used, products 4a or 4b are generated where the Bronsted acid is not observed but the alkyne is reduced to sp3 and forms a five-membered ring with Co center. Allenes (L6 and L7) lead to 5a(L6) and 5a(L7) where an allyl unit is coordinated to metal. In case of CpH (L8), compounds 6a and 6b
Cp # Co(S 2 C 2 B 10 H 10)(Cp # = Cp,1a ; MeCp,1b ; Me 4 Cp,1c ; Me 5 Cp,1d),丙酸甲酯(2)和报道了布朗斯台德酸有机配体(L1-L8)。1a和1b只能导致在碳硼烷上以环戊二烯基或甲基-环戊二烯基作为官能团在环境温度下进行选择性B-官能化,收率很高。根据所使用的布朗斯台德酸(L1-L8)的类型,可以获得四种包含B-C键的产品。如果选择了较强的配位体L1-L3,则可以分离化合物3a(L1-L3)和3b(L1-L3),其中L1-L3失去一个质子,从而为金属提供3个电子,炔烃被还原为烯烃。如果使用L4和L5,则生成产物4a或4b,其中未观察到布朗斯台德酸,但炔烃还原为sp 3并与Co中心形成一个五元环。烯丙基(L6和L7)导致5a(L6)和5a(L7),其中烯丙基单元与金属配位。在CpH(L8)的情况下,会生成含有原位的化
Electronic and Steric Effects in the Insertion of Alkynes into an Iridium(III) Hydride
作者:Xingwei Li、Tiffany Vogel、Christopher D. Incarvito、Robert H. Crabtree
DOI:10.1021/om049271z
日期:2005.1.1
relatively electron-rich alkynes (PhC⋮CH, PhCH2C⋮CH, and p-OMeC6H4C⋮CH), double insertion occurs stepwise, each alkyne undergoing rearrangement to a vinylidene intermediate independently to afford an iridium(III) η2-butadienyl. In the first alkyne insertion, deuterium labeling and crossover experiments confirm that the alkyne to vinylidene rearrangement is intraligand. Both a vinyl and a vinylidene intermediate
将多种炔烃插入反式-[IrH(PPh 3)2(C(Ph)CHC(O)Me)(丙酮)] +(1)的Ir-H键中会遵循三种不同的路线,具体取决于炔烃结构。对于相对富电子的炔烃(PhC⋮CH,PhCH 2 C⋮CH和p -OMeC 6 H 4 C⋮CH),分步进行两次插入,每个炔烃独立进行重排成亚乙烯基中间体,得到铱(III) η 2-丁二烯基。在第一次炔烃插入中,氘标记和交叉实验证实炔烃至亚乙烯基的重排是配体内。在第一次插入过程中,乙烯基中间体和亚乙烯基中间体均被捕获并分离。在第二次炔烃插入中,分离出CH有害中间体。贫电子炔烃(p -CF 3 C 6 H 4 C⋮CH和p -NO 2 C 6 H 4 C⋮CH)也经历两次插入1的过程,但使用p -CF 3 C 6 H 4进行氘标记实验C⋮CD表示可逆的C(sp)-H氧化加成。高极化炔烃[R 1 C⋮CC(O)R 2 ]插入1仅发生一次,即使R 1
Cu(I)-Catalyzed Cross-Coupling Rearrangements of Terminal Alkynes with Tropylium Tetrafluoroborate: Facile Access to Barbaralyl-Substituted Allenyl Acid Esters and 7-Alkynyl Cycloheptatrienes
cycloisomerization process from the π-alkyne–Cu(I) complex to afford the copper carbene intermediate, followed by migratory insertion with the second terminal alkyne to afford the barbaralyl-substituted allenyl acid esters. In addition, we develop a mild and highly efficient Cu(I)-catalyzed cross-coupling protocol to synthesize 7-alkynyl cycloheptatrienes that has a broad functional group tolerance and is applicable