β-H elimination is an intrinsic problem in transition metal-catalyzed reactions.We describe herein an interesting ligand effect for Et2Zn acting as either ethyl provider or H provider,respectively:by applying SPhos o...β-H elimination is an intrinsic problem in transition metal-catalyzed reactions.We describe herein an interesting ligand effect for Et2Zn acting as either ethyl provider or H provider,respectively:by applying SPhos or Gorlos-Phos as the ligand,β-H elimination has been successfully controlled in the corresponding Negishi coupling reaction affording different poly-substituted allenes in good yields and excellent selectivities.SAESI-MS (Solvent Assisted Electrospray Ionization Mass Spectrometry) has been applied to successfully capture the highly reactive organometallic intermediates,which show the different coordination behaviors of Pd with SPhos or Gorlos-Phos as the ligand in the catalytic cycle.In addition,the different reactivities of Int 1 and Int 2 towards the formation of the final allene products have been demonstrated via SAESI-MS/MS experiments.These MS studies visualized the whole catalytic cycle for the Negishi coupling reaction while nicely explain the observed reactivity and selectivity.展开更多
Summary of main observation and conclusion RhCI(PPh3)3-catalyzed [4+2] intramolecular cycloaddition of optically active axially chiral allene-dienes afforded c/s-fused [3.4.0]-bicyclic products with three chiral cente...Summary of main observation and conclusion RhCI(PPh3)3-catalyzed [4+2] intramolecular cycloaddition of optically active axially chiral allene-dienes afforded c/s-fused [3.4.0]-bicyclic products with three chiral centers in good yields with an excellent chemo-and diastereoselectivity. A pair of enantiomers of such products was gen erated highly selectively from both ena ntiomers of starting allene-die nes, indicati ng that the axial chirality dictated the absolute configurations of the three in situ generated chiral centers with a very high efficiency of chirality transfer.展开更多
Main observation and conclusion The first example of Rh-catalyzed kinetic resolution of 1,3-disubstituted allene-1,3-dienes involving intramolecular[4+2]-cycloaddition has been developed.Followed by C=C isomerization,...Main observation and conclusion The first example of Rh-catalyzed kinetic resolution of 1,3-disubstituted allene-1,3-dienes involving intramolecular[4+2]-cycloaddition has been developed.Followed by C=C isomerization,the reaction finally afforded aza-[4.3.0]bicyclic compounds with a very high en-antio-and E-selectivity.The mechanism has been unveiled by careful control experiments.The synthetic potentials of highly enanti-oenriched bicyclic products have also been demonstrated.展开更多
Summary of main observation and conclusion A highly eficient palladium-catalyzed direct coupling of propargylic alcohols with organoboronic acids to synthesize tri-and tetra-substituted llenes has been developed under...Summary of main observation and conclusion A highly eficient palladium-catalyzed direct coupling of propargylic alcohols with organoboronic acids to synthesize tri-and tetra-substituted llenes has been developed under mild reaction conditions.Many useful functional groups are tolerated in this pro-cess with high to excellent yields.Preliminary biological studies showed that several tri-and tetra-substituted allenes exhibited potent anti-diabetic activi-ties.展开更多
基金Financial supports from the National Natural Science Foundation of China(Grant No.21690063)the National Basic Re1search Program(2015CB856600)are greatly appreciated.
文摘β-H elimination is an intrinsic problem in transition metal-catalyzed reactions.We describe herein an interesting ligand effect for Et2Zn acting as either ethyl provider or H provider,respectively:by applying SPhos or Gorlos-Phos as the ligand,β-H elimination has been successfully controlled in the corresponding Negishi coupling reaction affording different poly-substituted allenes in good yields and excellent selectivities.SAESI-MS (Solvent Assisted Electrospray Ionization Mass Spectrometry) has been applied to successfully capture the highly reactive organometallic intermediates,which show the different coordination behaviors of Pd with SPhos or Gorlos-Phos as the ligand in the catalytic cycle.In addition,the different reactivities of Int 1 and Int 2 towards the formation of the final allene products have been demonstrated via SAESI-MS/MS experiments.These MS studies visualized the whole catalytic cycle for the Negishi coupling reaction while nicely explain the observed reactivity and selectivity.
基金the National Natural Science Foundation of China (No. 21690063).
文摘Summary of main observation and conclusion RhCI(PPh3)3-catalyzed [4+2] intramolecular cycloaddition of optically active axially chiral allene-dienes afforded c/s-fused [3.4.0]-bicyclic products with three chiral centers in good yields with an excellent chemo-and diastereoselectivity. A pair of enantiomers of such products was gen erated highly selectively from both ena ntiomers of starting allene-die nes, indicati ng that the axial chirality dictated the absolute configurations of the three in situ generated chiral centers with a very high efficiency of chirality transfer.
基金the National Natural Science Founda-tion of China(Grant No.21690063 for S.Ma and Grant No.21801041 for H.Qian)is greatly appreciated.We thank Mr.Feng Jiang in this group for reproducing the results of(3aS,7aS,E)-3h,(3aS,7aS,E)-3I,and(3aR,7aR,E)-3n presented in this study.
文摘Main observation and conclusion The first example of Rh-catalyzed kinetic resolution of 1,3-disubstituted allene-1,3-dienes involving intramolecular[4+2]-cycloaddition has been developed.Followed by C=C isomerization,the reaction finally afforded aza-[4.3.0]bicyclic compounds with a very high en-antio-and E-selectivity.The mechanism has been unveiled by careful control experiments.The synthetic potentials of highly enanti-oenriched bicyclic products have also been demonstrated.
基金Financial support from National Natural Science Foundation of China(Grant No.21690063 for S.Ma and Grant No.21801041 for H.Qian),and Shanghai Sailing Program(18YF1402000 for H.Qian)are greatly appreciated.We thank Mr.Junjie Fan in this group for reproducing the results of 3ag,3aj and 3ba presented in this study.
文摘Summary of main observation and conclusion A highly eficient palladium-catalyzed direct coupling of propargylic alcohols with organoboronic acids to synthesize tri-and tetra-substituted llenes has been developed under mild reaction conditions.Many useful functional groups are tolerated in this pro-cess with high to excellent yields.Preliminary biological studies showed that several tri-and tetra-substituted allenes exhibited potent anti-diabetic activi-ties.
