The catalytic bis‐allylation of alkynes is an important but challenging protocol to construct all‐carbon tetra‐substituted alkenes. Particularly, the catalytic unsymmetrical bis‐allylation of alkynes ...remains as an underexplored task to date. We herein report an unprecedented unsymmetrical bis‐allylation by simultaneously utilizing electrophilic trifluoromethyl alkene and nucleophilic allylboronate as the allylic reagents. With the aid of robust Ni0/NHC catalysis, valuable skipped trienes can be obtained in high regio‐ and stereo‐selectivities under mild conditions. Mechanistic studies indicate that the reaction may proceed through a β‐fluorine elimination of a nickelacycle followed by a transmetalation step with allylboronate. The present method exhibits a good tolerance of various functional groups. Besides, the skipped triene products can undergo an array of elaborate transformations, which highlights the potential applications of this strategy.
An efficient unsymmetrical bis‐allylation of alkynes has been developed by simultaneously utilizing electrophilic trifluoromethyl alkenes and nucleophilic allylboronates as the allylic reagents. With the aid of a robust Ni0/NHC catalysis, valuable skipped trienes can be obtained in high regio‐ and stereo‐selectivities under mild conditions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A distinct copper-catalyzed boroacylation of allenes with acyl chlorides and bis(pinacolato)diboron is developed. For aromatic acyl chlorides, 1,2-boroacylation of allenes readily takes place, ...leading to the formation of tetrasubstituted vinylboronates with exclusive (
E
)-stereoselectivity. In comparison, the employment of alkyl acyl chlorides as electrophiles alters the selectivity to 2,3-boroacylated products. Additionally, the product can easily undergo Suzuki-Miyaura cross-coupling to afford tetrasubstituted alkene with complete retention of the configuration.
A copper-catalyzed boroacylation of allenes with acyl chlorides and bis(pinacolato)diboron is developed for the synthesis of diverse tetrasubstituted vinylboronates with exclusive (
E
)-stereoselectivity.
A ruthenium-catalyzed allylic C(sp
3
)-H activation strategy has been employed to develop an intermolecular coupling of alkenyl sulfonamides with alkynes. This protocol features the ...diastereoselective construction of 3.3.0 and 4.3.0 bicyclic sultams in one step.
A ruthenium-catalyzed allylic C(sp
3
)-H activation strategy has been employed to develop an intermolecular coupling of alkenyl sulfonamides with alkynes.
In this article, we disclose a method for the regiodivergent and stereoselective hydrosilylation of isoprene using an Earth-abundant cobalt catalyst via variation of ligands. With a less sterically ...hindered bidentate ligand, the reactions proceeded through 4,1-hydrosilylation to afford allylsilanes in excellent regio- and stereoselectivities. By switching to a bulkier ligand, the reactions were efficiently diverted to 2,1-addition products for the first time. This regiodivergent protocol provides a modular approach for the construction of structurally diverse organosilanes with high atom economy and without the formation of stoichiometric byproducts.
A regiodivergent hydrophosphorylation of enynes with phosphites has been developed using earth-abundant nickel catalyst. The manipulation of regioselectivity can be achieved by regulating the ...insertion order of alkyne bonds with (RO)2P(O)–Ni–H or R2P(O)O–Ni–H species, respectively. Under the Ni/Xantphos catalysis, 4,1-hydrophosphorylation is selectively obtained while the adding of acid can promote reactions towards 1,2-addition. By employing an additional Pd–H catalysis, 2,1-hydrophosphorylation is also an accessible task in one-pot reaction. Mechanistic studies and analysis have also been performed to interpret the origin of the regioselective regulation. This work highlights the arts in accessing different regioisomers by diverting common elementary reaction steps.
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The Ni-catalyzed regiodivergent hydrophosphorylation of 1,3-enynes with phosphites has been developed through the regulation of common elementary reaction steps.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Butafulvene is a constitutional isomer of benzene, comprising a cyclobutene skeleton bearing two exocyclic conjugated methylene units. As a result of the intrinsic high strain energy and ...anti-aromaticity, the preparation of butafulvene compounds has been a fundamental issue for the development of butafulvene chemistry. Here an efficient palladium-catalysed coupling protocol involving propargylic compounds has been developed, providing a solid and versatile strategy for the rapid assembly of symmetric butafulvene derivatives. Based on mechanistic studies, two complementary mechanisms, both involving palladium catalysis, have been confirmed. With the mechanism unveiled, the synthesis of non-symmetric butafulvenes has also been achieved. Advantages of this strategy include tolerance to a wide range of propargylic molecules, mild reaction conditions, simple catalytic systems and easy scalability. The synthetic potential of the products as platform molecules for cyclobutene derivatives has also been demonstrated.Butafulvene is a constitutional isomer of benzene, comprising a cyclobutene skeleton bearing two exocyclic conjugated methylene units. Strategies for the synthesis of butafulvene compounds are currently limited due to its intrinsic high strain energy and anti-aromaticity. Now, palladium-catalysed couplings have been developed for the rapid assembly of symmetric and non-symmetric anti-aromatic butafulvene derivatives.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The catalytic bis‐allylation of alkynes is an important but challenging protocol to construct all‐carbon tetra‐substituted alkenes. Particularly, the catalytic unsymmetrical bis‐allylation of alkynes ...remains as an underexplored task to date. We herein report an unprecedented unsymmetrical bis‐allylation by simultaneously utilizing electrophilic trifluoromethyl alkene and nucleophilic allylboronate as the allylic reagents. With the aid of robust Ni0/NHC catalysis, valuable skipped trienes can be obtained in high regio‐ and stereo‐selectivities under mild conditions. Mechanistic studies indicate that the reaction may proceed through a β‐fluorine elimination of a nickelacycle followed by a transmetalation step with allylboronate. The present method exhibits a good tolerance of various functional groups. Besides, the skipped triene products can undergo an array of elaborate transformations, which highlights the potential applications of this strategy.
An efficient unsymmetrical bis‐allylation of alkynes has been developed by simultaneously utilizing electrophilic trifluoromethyl alkenes and nucleophilic allylboronates as the allylic reagents. With the aid of a robust Ni0/NHC catalysis, valuable skipped trienes can be obtained in high regio‐ and stereo‐selectivities under mild conditions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Alkali stress can cause severe crop damage and reduce production. However, physiological processes involved in alkali stress in oat seedlings are not well understood. In this study, physiological ...responses and yield of oat to alkali stress were studied using the alkali-tolerant oat genotype Vao-9 and the alkali-sensitive oat genotype Baiyan 5. The results were： （i） low concentrations of alkali stress （25 and 50 mmol L^-1） significantly reduced the yield and grain weight while increased the oat grain number per spike. A negative correlation between yield and malondialdehyde （MDA） content at the jointing and grain filling stages and positive correlations between yield on one hand and superoxide dismutase （SOD）, and peroxidase （POD） activities on the other at the jointing stage were observed. There was a positive correlation between MDA and soluble sugar at the grain filling stage; （ii） soluble sugar content was increased at the jointing and grain filling stages and decreased at the heading stage by alkali stress; （iii） alkali stress increased the SOD activity during the heading and grain filling stages, and increased the POD activity at the heading stage. As compared to the control, the increase of MDA contents in alkali-treated oat was observed, during the jointing, heading and grain filling stages; （iv） under alkali stress, the oat genotype Vao-9 showed higher antioxidant enzyme activity and lower soluble sugar contents during the heading stage, and lower MDA contents than those in the oat genotype Baiyan 5 under alkali stress. The result suggested that the high ROS scavenging capacity and soluble sugar levels might play roles in oat response to alkali stress,
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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