A C–H bond activation-based catalytic approach to tetrasubstituted chiral allenes

Wu, Shangze; Huang, Xin; Wu, Weiwei; Li, Pengbin; Fu, Chunling; Ma, Shengming

doi:10.1038/ncomms8946

Cited by 143 publications

(62 citation statements)

References 42 publications

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“…Another general method, organic compounds or polymer binders including ethylenediamine 20,21 , paraphenylene diamine 22 , poly(vinyl alcohol) 23 , poly (acrylic acid) 24 , polyurethane 17,18 and poly(dimethylsiloxane) 25 , had been reported to prepare CGS by crosslinking graphene oxide (GO) nanosheets and further reduction. Besides the two methods mentioned above, hydrothermal process was also employed to prepare CGS 16,27 , however high temperature, high pressure and special devices were necessary in the process. Besides the two methods mentioned above, hydrothermal process was also employed to prepare CGS 16,27 , however high temperature, high pressure and special devices were necessary in the process.…”

Section: Introductionmentioning

confidence: 99%

A facile method to prepare highly compressible three-dimensional graphene-only sponge

Zhao

Zhang

et al. 2015

J. Mater. Chem. A

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Endowing compressibility and conductivity into graphene sponge offers the possibility to regenerate piezoresistivity and is therefore of great interest in the field of sensor. In this work, the highly compressible threedimensional graphene-only sponge (CGS) was prepared through a facile method by using ammonium sulfide and ammonia solutions under mild condition. The morphologies and microstructures of the as-prepared CGSs can be controlled by adjusting the mass ratio of graphene oxide (GO) to ammonium sulfide which changed from metallic sheen bulk with leafshaped structure to a black sponge with cellular structure. Besides, by simply change the concentrations of GO, CGSs with different porosity, conductivity as well as mechanical strength were obtained. Moreover, the resultant CGSs show ultralow density (as low as 4.9 mg cm -3 ), high porosity (as much as 99.8%), great compressibility (as much as the strain of 80%), excellent stability (100 cycles) during the compression. Furthermore, the sensitive variation of electrical resistances and cycle stability were validated under the compressive strain of 50% which make them great candidates for pressureresponsive sensors, elastic conductors and other applications.Highly compressible three-dimensional graphene-only sponge (CGS) was prepared through a facile method. CGAs show ultralow density, high porosity, great compressibility, excellent stability which make them great candidates for pressure-responsive sensors, elastic conductors and other applications.

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Section: Introductionmentioning

confidence: 99%

A facile method to prepare highly compressible three-dimensional graphene-only sponge

Zhao

Zhang

et al. 2015

J. Mater. Chem. A

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“…As the alkyne insertion and the syn-β-oxygen elimination steps are stereospecific, enantioenriched coupling partners are employed to form chiral tetra-substituted allenes by chirality transfer. (Scheme 25) [39] …”

Section: Rhodium Catalysismentioning

confidence: 99%

A Simple and Versatile Amide Directing Group for C−H Functionalizations

et al. 2016

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Achieving selective C–H activation at a single and strategic site in the presence of multiple C–H bonds can provide a powerful and generally useful retrosynthetic disconnection. In this context, the directing group serves as a compass to guide the transition metal to C–H bonds using distance and geometry as powerful recognition parameters to distinguish between proximal and distal C–H bonds. However, the installation and removal of directing groups is a practical drawback. To improve the utility of this approach, one can seek solutions in three directions. First, simplifying the directing group; Second, use of common functional groups or protecting groups as directing groups; Third, attaching the directing group to substrates via a transient covalent bond to render directing groups catalytic. This review describes the rational development of an extremely simple and yet broadly applicable directing group for Pd(II), Rh(III) and Ru(II) catalysts, namely, the N-methoxy amide (CONHOMe). Through collective efforts in the community, a wide range of C–H activation transformations using this type of simple directing groups has been developed.

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“…9 As predicted by van’t Hoff in 1875, 1 the orthogonal relationship between the adjacent π systems within the allene structure gives rise to the possibility of axial chirality, which has inspired the development of methods that enable the enantioselective synthesis of allenes. 10–12 Traditional approaches have typically involved the stereospecific transformation of chiral propargylic precursors, such as [3,3] 13,14 and [2,3] 15 sigma-tropic rearrangements, S N 2′ displacements, 16–22 and reductive transposition. 23 Strategies using stoichiometric chiral reagents have also been developed, 24 as well as those employing kinetic resolution of preformed racemic allenes.…”

Section: Introductionmentioning

confidence: 99%

Enantioselective Synthesis of Allenes by Catalytic Traceless Petasis Reactions

et al. 2017

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Allenes are useful functional groups in synthesis as a result of their inherent chemical properties and established reactivity patterns. One property of chemical bonding renders 1,3-substituted allenes chiral, making them attractive targets for asymmetric synthesis. While there are many enantioselective methods to synthesize chiral allenes from chiral starting materials, fewer methods exist to directly synthesize enantioenriched chiral allenes from achiral precursors. We report here an asymmetric boronate addition to sulfonyl hydrazones catalyzed by chiral biphenols to access enantioenriched allenes in a traceless Petasis reaction. The resulting Mannich product from nucleophilic addition eliminates sulfinic acid, yielding a propargylic diazene that performs an alkyne walk to afford the allene. Two enantioselective approaches have been developed; alkynyl boronates add to glycolaldehyde imine to afford allylic hydroxyl allenes, and allyl boronates add to alkynyl imines to form 1,3-alkenyl allenes. In both cases, the products are obtained in high yields and enantioselectivities.

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A C–H bond activation-based catalytic approach to tetrasubstituted chiral allenes

Cited by 143 publications

References 42 publications

A facile method to prepare highly compressible three-dimensional graphene-only sponge

A facile method to prepare highly compressible three-dimensional graphene-only sponge

A Simple and Versatile Amide Directing Group for C−H Functionalizations

Enantioselective Synthesis of Allenes by Catalytic Traceless Petasis Reactions

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