Copper-catalyzed regioselective hydroboration of terminal alkynes in aqueous medium

Yao, Zhonghua; Hong, Shibin; Zhang, Wei; Liu, Mengyan; Deng, Wei

doi:10.1016/j.tetlet.2016.01.049

Cited by 32 publications

(12 citation statements)

References 48 publications

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“…Upon removing the solvent, a clear oil was identified as (E)-2-(hex-1-enyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (0.985 g, 93%) was isolated. 11 cyclohexylvinyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane was isolated. 13 were combined in a 20 mL scintillation vial.…”

Section: S15mentioning

confidence: 99%

“…Upon removing the solvent, a clear oil identified as (E)-4,4,5,5-tetramethyl-2-(5-methylhex-1-enyl)-1,3,2-dioxaborolane (1.028 g, 85%) was obtained. 11 (0.00569 mmol), stirred for 2 h, and exposed to air to deactivate the catalyst. Greater than 99%…”

Section: S15mentioning

confidence: 99%

“…The crude material was purified using silica gel column chromatography with 20:1 hexane:ethyl acetate as the eluent. Upon removing the solvent, a yellow oil identified as (E)-4,4,5,5-tetramethyl-2-(4methylstyryl)-1,3,2-dioxaborolane (0.0823 g, 69%) was isolated 11. 1 H NMR (chloroform-d, 400…”

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confidence: 99%

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Hydroboration of alkynes and nitriles using an α-diimine cobalt hydride catalyst

et al. 2017

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Section: S15mentioning

confidence: 99%

Section: S15mentioning

confidence: 99%

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Hydroboration of alkynes and nitriles using an α-diimine cobalt hydride catalyst

et al. 2017

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“…2‐(1‐Cyclopropylvinyl)‐4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane (9e): A mixture of ethynylcyclopropane (40.0 g, 605 mmol), KOAc (52.3 g, 533 mmol), LiCl (14.4, 339 mmol), CuBr (76.5 g, 533 mmol) and B 2 pin 2 (135 g, 533 mmol) in DMF (1.2 L) was stirred at 25 °C overnight. The resulting solution was extracted with hexane (2 × 1.2 L), and the combined hexane layers were concentrated under vacuum.…”

Section: Methodsmentioning

confidence: 99%

gem‐Difluorocyclopropanation of Alkenyl Trifluoroborates with the CF₃SiMe₃–NaI System

et al. 2020

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Difluorocyclopropanation of alkenyl trifluoroborates using TMSCF 3 -NaI system was reported for the first time. The developed method allowed preparation of monocyclic, spiroand fused-bicyclic gem-difluorocyclopropanes bearing addi-groups. [20][21][22][23][24] Nonetheless, the addition of difluorocarbene equivalent derived from TMSCF 3 to alkenylboronic derivatives was unknown until the present study. Scheme 1. Difluorocyclopropanation of alkenylboronic derivatives.In this work, application of TMSCF 3 -NaI system in refluxing THF (66°C) for the synthesis of gem-difluorocyclopropyl boronic derivatives and its effectiveness for multigram scale synthesis is reported (Scheme 1). It is shown that alkenyl trifluoroborates are optimal substrates for the preparation of aliphatic derivatives which facilitate isolation of the target products. The studied reaction scope included substrates bearing secondary N-Boc protected amine, ester, ether, phenyl and cyclopropyl moieties and provided products with spiro-and fused-bicyclic molecular topologies. Results and DiscussionOur study commenced with testing TMSCF 3 -NaI system in reaction with substrate 5a (Scheme 2), for which the difluorocyclopropanation using XCF 2 CO 2 Na (X = Cl, Br) at 180°C and 150°C, Scheme 2. Attempted difluorocyclopropanation of alkenyl boronic derivatives using the TMSCF 3 -NaI system. 2218Scheme 3. Preparation of trifluoroborate salts 7 from pinacolboronates 9.Scheme 4. Synthesis of pinacolboronates 9e (A) and 9p (B).

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“…[17] Remarkably,i nversions of regioselectivities have been observed, particularly by introducing different copper ligands. [18][19][20][21][22][23] Foraryl-substituted terminal alkynes,and with non-bulky ligands,the selectivity is generally in favor of the linear adduct (or b-product, Table 1). [24] An inversion of this trend was observed by Hoveyda with the bulky N-aryl NHC ligand SIPr, which favored the formation of the branched adduct.…”

Section: Encapsulated Metal Complexes Show Distinctive Behaviorsmentioning

confidence: 99%

Cyclodextrin Cavity‐Induced Mechanistic Switch in Copper‐Catalyzed Hydroboration

et al. 2017

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Encapsulated metal complexes show distinctive behaviors resulting from the confinement of the metal.[1] The cavity plays the role of second coordination sphere, which impacts reactivity and selectivity. [2][3][4][5][6][7] Alterations in regioselectivity were observed with encapsulated metal catalysts in hydratation or hydroformylation reactions. [8][9][10][11] An unusual coordination mode of the complex imposed by the confinement, or a controlled approach of the substrate imposed by sterics have been raised to explain the changes. Hence, regioselectivity is influenced by confinement of the reactive center but the reaction mechanism itself was not invoked. We present here a system in which not only the regioselectivity can be switched by only changing the size of a cavity but also the actual mechanism of the reaction. We also demonstrate another benefit of encapsulation in the discovery of new mechanisms.In the framework of our studies on cyclodextrin (CD)-based metal catalysts, [12] we developed N-heterocyclic carbene (NHC)-capped CD complexes, called (ICyD)M, where the metal is literally wrapped by the CD scaffold.[13] The position of an appended metal inside this cavity forces external ligands to be influenced by its shape to interact with the metal center. Thus, these particular structures were found to induce shapedependent enantio-and regioselectivities in gold-catalyzed cycloisomerisation reactions. [14] Structural analyses of (-ICyD)M and (-ICyD)M complexes, derived from  and -CD, respectively, revealed significant differences in shape, in particular in the close surroundings of the metal. For instance, -and -ICyD-based complexes both present a groove leading to the metal, but for (-ICyD)M, a pit situated next to the metallic center is observed whereas the metal is tightly wrapped in (-ICyD)M (Figure 1). [14] This suggests that a lateral approach to the metal may be conceivable for (-ICyD)M complexes but precluded for

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Copper-catalyzed regioselective hydroboration of terminal alkynes in aqueous medium

Abstract: A mild and environment-friendly strategy of copper-catalyzed regioselective hydroboration of terminal alkynes in aqueous medium was developed.

Cited by 32 publications

References 48 publications

Hydroboration of alkynes and nitriles using an α-diimine cobalt hydride catalyst

Hydroboration of alkynes and nitriles using an α-diimine cobalt hydride catalyst

gem‐Difluorocyclopropanation of Alkenyl Trifluoroborates with the CF₃SiMe₃–NaI System

Cyclodextrin Cavity‐Induced Mechanistic Switch in Copper‐Catalyzed Hydroboration

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Copper-catalyzed regioselective hydroboration of terminal alkynes in aqueous medium

Abstract: A mild and environment-friendly strategy of copper-catalyzed regioselective hydroboration of terminal alkynes in aqueous medium was developed.

Cited by 32 publications

References 48 publications

Hydroboration of alkynes and nitriles using an α-diimine cobalt hydride catalyst

Hydroboration of alkynes and nitriles using an α-diimine cobalt hydride catalyst

gem‐Difluorocyclopropanation of Alkenyl Trifluoroborates with the CF3SiMe3–NaI System

Cyclodextrin Cavity‐Induced Mechanistic Switch in Copper‐Catalyzed Hydroboration

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gem‐Difluorocyclopropanation of Alkenyl Trifluoroborates with the CF₃SiMe₃–NaI System