- A CONVENIENT ROUTE TO SYMMETRIC 1,1-DIALKYLETHENES FROM 1,2-DIMETHOXYETHENYLLITHIUM AND TRIALKYLBORANES
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1,1-Dialkylethenes are prepared from 1,2-dimethoxyethenyllithium and organoboranes by treatment with trichloroacetic acid and then with sodium acetate-acetic anhydride and TiCl4/Ti(OPri)4.
- Yogo, Toshinobu,Suzuki, Akira
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- Controllable, Sequential, and Stereoselective C-H Allylic Alkylation of Alkenes
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The direct conversion of C-H bonds into new C-C bonds represents a powerful approach to generate complex molecules from simple starting materials. However, a general and controllable method for the sequential conversion of a methyl group into a fully substituted carbon center remains a challenge. We report a new method for the selective and sequential replacement of three C-H bonds at the allylic position of propylene and other simple terminal alkenes with different carbon groups derived from Grignard reagents. A copper catalyst and electron-rich biaryl phosphine ligand facilitate the formation of allylic alkylation products in high branch selectivity. We also present conditions for the generation of enantioenriched allylic alkylation products in the presence of catalytic copper and a chiral phosphine ligand. With this approach, diverse and complex products with substituted carbon centers can be generated from simple and abundant feedstock chemicals.
- Qin, Ling,Sharique, Mohammed,Tambar, Uttam K.
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supporting information
p. 17305 - 17313
(2019/11/03)
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- Mild Ring-Opening 1,3-Hydroborations of Non-Activated Cyclopropanes
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The Brown hydroboration reaction, first reported in 1957, is the addition of B?H across an olefin in an anti-Markovnikov fashion. Here, we solved a long-standing problem on mild 1,3-hydroborations of non-activated cyclopropanes. A three-component system including cyclopropanes, boron halides, and hydrosilanes has been developed for borylative ring-opening of cyclopropanes following the anti-Markovnikov rule, under mild reaction conditions. Density functional theory (M06-2X) calculations show that the preferred pathway involves a cationic boron intermediate which is quenched by hydride transfer from the silane.
- Wang, Di,Xue, Xiao-Song,Houk, Kendall N.,Shi, Zhuangzhi
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supporting information
p. 16861 - 16865
(2018/11/27)
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- B(C6F5)3-Catalyzed Ring Opening and Isomerization of Unactivated Cyclopropanes
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Catalytic amounts of B(C6F5)3 promote the ring opening and subsequent isomerization of a series of unactivated cyclopropanes to afford terminal olefins in good yields when a hydrosilane and 2,6-dibromopyridine are employed as additives.
- Zhang, Zi-Yu,Liu, Zhi-Yun,Guo, Rui-Ting,Zhao, Yu-Quan,Li, Xiang,Wang, Xiao-Chen
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supporting information
p. 4028 - 4032
(2017/03/27)
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- Rh(II)-Catalyzed [2,3]-Sigmatropic Rearrangement of Sulfur Ylides Derived from Cyclopropenes and Sulfides
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(Chemical Equation Presented) A new type of Rh2(OAc)4-catalyzed [2,3]-sigmatropic rearrangement of sulfur ylides is reported. A series of cyclopropenes were successfully employed for [2,3]-sigmatropic rearrangement by a reaction with either allylic or propargylic sulfides. Under the optimized conditions, the reaction afforded the products in moderate to excellent yields. In these transformations, the vinyl metal carbenes generated in situ from the cyclopropenes were effectively trapped by sulfides, resulting in the formation of corresponding products upon [2,3]-sigmatropic rearrangements.
- Zhang, Hang,Wang, Bo,Yi, Heng,Zhang, Yan,Wang, Jianbo
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supporting information
p. 3322 - 3325
(2015/07/15)
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- One-pot conversion of terminal alkynes into gem-disubstituted-alkenes
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A one-pot reaction of terminal alkynes with in situ generated hydrogen iodide and organozinc compounds in the presence of Pd(PPh3)4 provided a simple and useful method for the preparation of gem-disubstituted-alkenes.
- Luo, Fen-Tair,Fwu, Shiang-Long,Huang, Wen-Shu
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p. 6839 - 6840
(2007/10/02)
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