Iron-Catalyzed Alkenylzincation of Internal Alkynes

The alkenylzincation of internal alkynes is an effective method for the synthesis of multi-substituted conjugated dienes;however,the current catalytic systems for this reaction are limited in terms of substrate scope and selectivity control,which restricts its practical applications.Herein,we report the first iron-catalyzed alkenylzincation of internal alkynes,which features mild conditions,simple operation,broad substrate scope (including aryl/alkyl,diaryl,and dialkyl acetylenes),excellent functional group tolerance (tolerating highly active functional groups such as ester,methylthio,amide,sulfonyl,cyano,etc.),and high activity (with a turnover number of up to 11500,the highest record for carbometallation reactions).Notably,the catalytic system described in this article also realized the highly selective vinylzincation of unfunctionalized internal alkynes as well as the alkenylzincation of unsymmetrical diarylacetylenes and dialkyl acetylenes,which have not been achieved with other catalytic systems reported in the literatures.The current study provides a highly selective access to synthetically important multi-substituted conjugated dienes.

Well-defined coordination environment breaks the bottleneck of organic synthesis:Single-atom palladium catalyzed hydrosilylation of internal alkynes

Single-atom site(SAS)catalysts have attracted considerable attention due to their excellent performance.However,most of the current research models of SAS catalysts are based on inorganic catalysts,where“metal and coordination atom interaction”cannot simulate the fine-tuning effect of organic ligands on metal catalytic centers in homogeneous catalysts.Therefore,certain chemical transformations in homogeneous catalysis cannot be perfectly replicated.Here,we used porous organic ligand polymers as the carrier,which effectively changes the charge regulation of nanoparticles and monoatomic metal catalysts.Drawing lessons from traditional homogeneous metal/ligand catalysis,we introduced various functional groups into the ligand polymers to adjust the electronic properties,and successfully realized the hydrosilylation of internal alkynes with high catalytic performance.The selectivity and catalytic efficiency under the Pd@POL-1 catalyst system were improved compared with previous studies.The internal alkynes with various structures can complete this reaction,and the ratio of E/Zcan reach up to 100:1.

Spiro(phosphoamidite) ligand(SIPHOS)/Cu(OTf)2-catalyzed highly regio-and stereo-selective hydroborations of internal alkynes with diborane in water

The highly regio-and stereoselective hydroborations of unactivated internal alkynes with diboron compound catalyzed by Cu（OTf）2 with spiro（phosphoamidite） as ligand in the presence of Cs2CO3 in water was developed.This protocol was applied efficiently in the aqueous synthesis of multi-substituted vinylboranes.

Theoretical Study of 1,3-Dipolar Cycloaddition of Hydrazoic Acid to Substituted Ynamines

The 1,3-dipolar cycloaddition reactions of various substituted ynamines with hydrazoic acid were theoretically investigated with the high-accuracy CBS-QB3 method. Two regioisomers, 4-amine, and 5-amine substituted adducts, were obtained, with the former as the preferred yield. This regioselectivity is rationalized by the frontier molecular orbital theory. The reactivity and synchronicity are enhanced with the increase of the electron-withdrawing character of the substitute on ynamine fragment. The calculations also show that the effect of solvent increases the activation energy, and the reaction becomes even harder in polar solvent.

Catalytic C-N Bond Alkynylation of N-Benzylic Sulfonamides with Terminal Alkynes

A new cross-coupling reaction of N-benzylic sulfonamides with terminal alkynes for the synthesis of internal alkynes is reported.In the presence of 5 mol%of(Tf)_(2)NH/Bi(OTf)_(3)(1∶1),a broad range of N-benzylic sulfona-mides react smoothly with arylacetylenes to afford structurally diverse internal alkynes in moderate to excellent yields.We reasoned that vinyl cations could be formed by the regioselective attack of terminal alkynes with benzyl cations generated in situ from N-benzylic sulfonamides under acidic conditions,which then eliminated to form a carbon-carbon triple bond.

Dual Palladium/Scandium Catalysis toward Rotationally Hindered C3-Naphthylated Indoles from β-Alkynyl Ketones and o-Alkynyl Anilines

A new dual plldium/scandium catalysis starting fromβ-alkynyl ketones and o alkynyl anilines is reported for the first time,leading to the atom-economic synthesis of rotationally hindered C3-naphthylated indoles in moderate to good yields and high regioselectivi-ty.This method can tolerate normal air conditions,and features the use of palladium/scandium cooperative catalysts without any ligand,facile double annulation involving various internal alkynes,and good functional group tolerance.