A highly efficient and selective[2+2+2]cyclization of diynes and monoalkynes was catalyzed by rhodium under room temperature in water/THF mixed solvent,affording isoindolines and isobenzofurans in good to excellent yi...A highly efficient and selective[2+2+2]cyclization of diynes and monoalkynes was catalyzed by rhodium under room temperature in water/THF mixed solvent,affording isoindolines and isobenzofurans in good to excellent yields.The center atoms (N,O) in the diynes showed a significant effect for the cyclization.展开更多
Polycyclotrimerization of diynes was explored as a new route to hyperbranched polymers in this investigation. Polymerization of terminal diynes of 1,8-nonadiyne and 1,9-decadiyne was studied using TaCl5, NbCl5, Mo(CO)...Polycyclotrimerization of diynes was explored as a new route to hyperbranched polymers in this investigation. Polymerization of terminal diynes of 1,8-nonadiyne and 1,9-decadiyne was studied using TaCl5, NbCl5, Mo(CO)(4)(nbd) and [Mo(CO)(3)cp](2) as catalysts (where nbd = 2,5-norbornadiene, cp = cyclopentadiene). A soluble polymer was obtained when the polymerization of 1,9-decadiyne was initiated by TaCl5 at low temperature (0 degrees C). The polymer, however, became partially soluble after purification, possibly due to the postpolymerization-induced crosslinking. NbCl5-catalyzed polymerization of 1,9-bis(trimethylsilyl)- 1,8-nonadiyne gave a completely soluble polymer. Soluble polymers were also obtained from the polymerization of 3,9-dodecadiyne initiated by NbCl5, Mo(CO)(4)(nbd), [Mo(CO)(3)cp](2), PdCl2-ClSiMe3 and Pd/C-ClSiMe3. IR, UV, and NMR spectroscopic analysis revealed that different catalysts gave polymers with different structures, ranging from linear polyenes to hyperbranched polyphenylenes. The polymers absorb UV light at around 250 nm and emit fluorescence at 340 nm when they are excited at 248 nm.展开更多
We report a Pd-catalyzed halocyclization of unactivated 1,6-diynes with N-bromosuccinimide(NBS).This approach produces stereo-defined dibromo substituted dihydropyrans,tetrahydropyridines,and 3-methylene cyclohexenes ...We report a Pd-catalyzed halocyclization of unactivated 1,6-diynes with N-bromosuccinimide(NBS).This approach produces stereo-defined dibromo substituted dihydropyrans,tetrahydropyridines,and 3-methylene cyclohexenes with exocyclic double bond appendages in mostly good yields.Copper salt was found to be a useful Lewis acid in this reaction.Mechanistically,a formal anti-carbopalladation and a bromide radical promoted PdⅡ-PdⅢ-PdⅠ-PdⅡcatalytic cycles were proposed to be involved in the formation of the dibromo-substituted products.Further functionalization of the dihydropyran derivatives underwent B(C6F5)3-catalyzed ring opening,and reduction afforded dibrominated 1,3-dienes with excellent stereoselectivity.展开更多
Symmetrical diynes were synthesized by ligand-free copper-catalyzed homocoupling reaction of 1,1-dibromo-1- alkenes using a DBU/DMSO system at room temperature in good to excellent yields.
The Meinwald rearrangement has proven to be one of the most useful tools in organic synthesis.However,examples of asymmetric Meinwald rearrangements are quite scarce,and these reactions have so far been limited to the...The Meinwald rearrangement has proven to be one of the most useful tools in organic synthesis.However,examples of asymmetric Meinwald rearrangements are quite scarce,and these reactions have so far been limited to the use of chiral Br?nsted acids as catalysts.Here,we report a copper-catalyzed asymmetric cascade cyclization/Meinwald rearrangement reaction,allowing the practical and atom-economic synthesis of a range of chiral tricyclic pyrroles bearing a chiral oxa-quaternary carbon stereocenter in high yields and enantioselectivities.Thus,this protocol not only represents the first transition-metal-catalyzed enantioselective Meinwald rearrangement,but also constitutes the first example of asymmetric formal monocarbon insertion into C-O bond of ester.Moreover,theoretical calculations provide further evidence for this multiple cascade cyclization and elucidate the origin of enantioselectivity.展开更多
Reaction of [η5:σ-Me2C(C5H4)(C2B10H10)]Ru(NCCH3)2 (1) with R1C≡CR1(R1 = Et, Ph) in toluene at 80 °C yielded organoruthenium cyclobutadiene complexes [η5:σ-Me2C(C5H4)(C2B10H10)]Ru(-4-C4R14) in 】80% yield. Tr...Reaction of [η5:σ-Me2C(C5H4)(C2B10H10)]Ru(NCCH3)2 (1) with R1C≡CR1(R1 = Et, Ph) in toluene at 80 °C yielded organoruthenium cyclobutadiene complexes [η5:σ-Me2C(C5H4)(C2B10H10)]Ru(-4-C4R14) in 】80% yield. Treatment of 1 with diynes R2C≡C(CH2)3C≡CR2 (R2 = Me, Et) in toluene at room temperature yielded ruthenacyclopentatrienes [η5:σ-Me2C (C5H4)(C2B10H10)]Ru[=C2(R2)2C2(CH2)3] in 】85% yield. These new complexes were fully characterized by various spectroscopic techniques, elemental analyses and single-crystal X-ray diffraction studies. The possible reaction mechanism was proposed.展开更多
文摘A highly efficient and selective[2+2+2]cyclization of diynes and monoalkynes was catalyzed by rhodium under room temperature in water/THF mixed solvent,affording isoindolines and isobenzofurans in good to excellent yields.The center atoms (N,O) in the diynes showed a significant effect for the cyclization.
基金This workw was in part supported by the Earmarked Research Grants of the Hong Kong Research Grants Council(HKUST6062/98P and HKUST6149/97P)
文摘Polycyclotrimerization of diynes was explored as a new route to hyperbranched polymers in this investigation. Polymerization of terminal diynes of 1,8-nonadiyne and 1,9-decadiyne was studied using TaCl5, NbCl5, Mo(CO)(4)(nbd) and [Mo(CO)(3)cp](2) as catalysts (where nbd = 2,5-norbornadiene, cp = cyclopentadiene). A soluble polymer was obtained when the polymerization of 1,9-decadiyne was initiated by TaCl5 at low temperature (0 degrees C). The polymer, however, became partially soluble after purification, possibly due to the postpolymerization-induced crosslinking. NbCl5-catalyzed polymerization of 1,9-bis(trimethylsilyl)- 1,8-nonadiyne gave a completely soluble polymer. Soluble polymers were also obtained from the polymerization of 3,9-dodecadiyne initiated by NbCl5, Mo(CO)(4)(nbd), [Mo(CO)(3)cp](2), PdCl2-ClSiMe3 and Pd/C-ClSiMe3. IR, UV, and NMR spectroscopic analysis revealed that different catalysts gave polymers with different structures, ranging from linear polyenes to hyperbranched polyphenylenes. The polymers absorb UV light at around 250 nm and emit fluorescence at 340 nm when they are excited at 248 nm.
基金National Natural Science Foundation of China(No.21961015)the Natural Science Foundation of Jiangxi Province(No.20202ACBL203005)for financial supportthe Open Project Program of Polymer Engineering Research Center,Jiangxi Science&Technology Normal University(No.KFGJ18014)。
文摘We report a Pd-catalyzed halocyclization of unactivated 1,6-diynes with N-bromosuccinimide(NBS).This approach produces stereo-defined dibromo substituted dihydropyrans,tetrahydropyridines,and 3-methylene cyclohexenes with exocyclic double bond appendages in mostly good yields.Copper salt was found to be a useful Lewis acid in this reaction.Mechanistically,a formal anti-carbopalladation and a bromide radical promoted PdⅡ-PdⅢ-PdⅠ-PdⅡcatalytic cycles were proposed to be involved in the formation of the dibromo-substituted products.Further functionalization of the dihydropyran derivatives underwent B(C6F5)3-catalyzed ring opening,and reduction afforded dibrominated 1,3-dienes with excellent stereoselectivity.
基金Project supported by the National Natural Science Foundation of China （No. 30873153）, and the Key Projects of Shanghai in Biomedical （No. 08431902700）.
文摘Symmetrical diynes were synthesized by ligand-free copper-catalyzed homocoupling reaction of 1,1-dibromo-1- alkenes using a DBU/DMSO system at room temperature in good to excellent yields.
基金financial support from the National Natural Science Foundation of China(Nos.22125108,22101238,22331004 and 22121001)Yunnan Fundamental Research Project(No.202401CF070024)+2 种基金Natural Science Foundation of Jiangsu Province(No.BK20211059)the Project of Science and Technology of Xuzhou Government(No.KC22080)NFFTBS(No.J1310024)。
文摘The Meinwald rearrangement has proven to be one of the most useful tools in organic synthesis.However,examples of asymmetric Meinwald rearrangements are quite scarce,and these reactions have so far been limited to the use of chiral Br?nsted acids as catalysts.Here,we report a copper-catalyzed asymmetric cascade cyclization/Meinwald rearrangement reaction,allowing the practical and atom-economic synthesis of a range of chiral tricyclic pyrroles bearing a chiral oxa-quaternary carbon stereocenter in high yields and enantioselectivities.Thus,this protocol not only represents the first transition-metal-catalyzed enantioselective Meinwald rearrangement,but also constitutes the first example of asymmetric formal monocarbon insertion into C-O bond of ester.Moreover,theoretical calculations provide further evidence for this multiple cascade cyclization and elucidate the origin of enantioselectivity.
基金supported by the Research Grants Council of The Hong Kong Special Administration Region (403907)
文摘Reaction of [η5:σ-Me2C(C5H4)(C2B10H10)]Ru(NCCH3)2 (1) with R1C≡CR1(R1 = Et, Ph) in toluene at 80 °C yielded organoruthenium cyclobutadiene complexes [η5:σ-Me2C(C5H4)(C2B10H10)]Ru(-4-C4R14) in 】80% yield. Treatment of 1 with diynes R2C≡C(CH2)3C≡CR2 (R2 = Me, Et) in toluene at room temperature yielded ruthenacyclopentatrienes [η5:σ-Me2C (C5H4)(C2B10H10)]Ru[=C2(R2)2C2(CH2)3] in 】85% yield. These new complexes were fully characterized by various spectroscopic techniques, elemental analyses and single-crystal X-ray diffraction studies. The possible reaction mechanism was proposed.
