Tuning of the textural features and acidic properties of sulfated mesoporous lanthana-zirconia solid acid catalysts for alkenylation of diverse aromatics to their corresponding α-arylstyrenes

The textural features and acidic properties of sulfated mesoporous lanthana‐zirconia solid acids （SO42？/meso‐La0.1Zr0.9Oδ） were efficiently tuned by modifying the conditions used to prepare the meso‐La0.1Zr0.9Oδcomposites, such as the molar ratio of the template to La and Zr metal ions （Nt/m）, molar ratio of ammonia to La and Zr metal ions （Na/m）, hydrothermal temperature （Thydro）, and hy‐drothermal time （thydro）. The effect of the textural features and acidic properties on the catalytic performance of solid acid catalysts for alkenylation of p‐xylene with phenylacetylene was investi‐gated. Various characterization techniques such as N2 physisorption, X‐ray diffraction, NH3 temper‐ature‐programmed desorption, and thermogravimetric analysis were employed to reveal the rela‐tionship between the nature of catalyst and its catalytic performance. It was found that the catalytic performance significantly depended on the textural features and acidic properties, which were strongly affected by preparation conditions of the meso‐La0.1Zr0.9Oδcomposite. Appropriate acidic sites and high accessibility were required to obtain satisfactory catalytic reactions for this reaction. It was also found that the average crystallite size of t‐ZrO2 affected by the preparation conditions had significant influence on the ultrastrong acidic sites of the catalysts. The optimized SO42？/meso‐La0.1Zr0.9Oδcatalyst exhibited much superior catalytic activity and coke‐resistant stabil‐ity. Moreover, the developed SO42？/meso‐La0.1Zr0.9Oδcatalyst demonstrated excellent catalytic per‐formance for alkenylation of diverse aromatics with phenylacetylene to their correspondingα‐arylstyrenes. Combining the previously established complete regeneration of used catalysts by a facile calcination process with the improved catalytic properties, the developed SO42？/meso‐La0.1Zr0.9Oδ solid acid could be a potential catalyst for industrial production ofα‐arylstyrenes through clean and atom efficient solid‐acid‐mediated Friedel‐Crafts alkenylation of diverse aromatics with phenylacetylene.

Ceria-modified hierarchical Hβ zeolite as a robust solid acid catalyst for alkenylation of p-xylene with phenylacetylene

A ceria‐modified hierarchical Hβzeolite was prepared by a desilication‐dealumination procedure followed by ceria modification.The catalytic performance of the ceria‐modified and unmodified hierarchical Hβzeolite catalysts for alkenylation of p‐xylene with phenylacetylene was investigated.Various characterization techniques,including X‐ray diffraction,X‐ray fluorescence,nitrogen adsorption‐desorption,and NH3temperature‐programmed desorption,were used to examine the structure‐performance relationships.Our results show that the optimized ceria‐modified hierarchical Hβzeolite catalyst demonstrated higher catalytic activity,selectivity,and stability for alkenylation of p‐xylene with phenylacetylene than those of pristine Hβzeolite.This performance was attributed to more acidic sites and improved accessibility to active sites through larger pores,together with a higher mesoporous surface area and volume resulting from the hierarchical pore architecture and ceria modification.Thus,our5wt%CeO2‐Hβ‐B0.2A0.2catalyst shows great potential for producing alkenyl aromatics through solid acid catalyzed alkenylation.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved

Strain-promoted S-arylation and alkenylation of sulfinamides using arynes and cyclic alkynes

The conversion of commercially available chiral sulfinamides into pharmaceutically useful chiral sulfoximines via direct SIVfunctionalization is synthetically attractive but challenging due to the competitive reaction of N-functionalization. Herein, we disclose a novel strain-release strategy to access stereospecific and chemoselective SIV-arylation and alkenylation of sulfinamides using arynes and strained cyclic alkynes. This method tolerates an unprecedented chemical diversity of functional groups attached to the nitrogen center(N-R). The origin of the high SIV-selectivity is elucidated by density functional theory calculations, suggesting a stepwise mechanism for the aryne substrates and a concerted mechanism for the cyclic alkynes.

Rh(Ⅲ)-catalyzed late-stage C-H alkenylation and macrolactamization for the synthesis of cyclic peptides with unique Trp(C7)-alkene crosslinks

Heterocycle-braced cyclic peptides have demonstrated enhanced metabolic stability,increased potency and selectivity.Here,we present a rapid synthesis method for constructing Trp(C7)-alkene(E)-crosslinked cyclic peptides with potent anti-proliferative activities against cancer cells,through C-H alkenylation and macrolactamization.This report addresses critical challenges associated with the installation and removal of the directing group N-Piv,configuration selectivity of the olefin,and intramolecular cyclization.No-tably,this method exhibits mild reaction conditions,traceless removal of the directing group,and high configuration selectivity.

Asymmetric alkenylation reaction of benzoxazinones with diarylethylenes catalyzed by B(C_(6)F_(5))_(3)/chiral phosphoric acid

Catalytic enantioselective alkenylation is an efficient method to construct chiral alkene molecules,but the asymmetric alkenylation of simple alkenes catalyzed by metal-free catalysts remains an elusive challenge.Herein,we reported an asymmetric alkenylation of benzoxazinones with diarylethylenes by utilizing a B(C_(6)F_(5))_(3)/chiral phosphoric acid catalyst.A broad of benzoxazinones and diarylethylenes with electron-withdrawing and electron-donating groups were tolerated(up to 95%yield and 97.5:2.5 e.r.)in the methodology under mild reaction conditions.Moreover,the synthetic utility was confirmed by the scaled-up reaction and transformations of the products.The mechanism was preliminarily explored by control reactions,nonlinear effect experiment and DFT calculations.

Spherical hollow mesoporous silica supported phosphotungstic acid as a promising catalyst for α-arylstyrenes synthesis via Friedel-Crafts alkenylation

In this work, a spherical hollow mesoporous silica(SHMS) with high surface area(902 m^2/g) and large mesopore volume(1.31 cm^3/g) was prepared via a facile and scalable two-step soft-hard dual templateassisted sol-gel approach(OSDSG) by using glucose-derived carbon nano/micro particles(NMCP) as a hard template and cetyltrimethylammonium bromide(CTAB) as a soft template,respectively,in which the size-preselected carbon submicro-particle was used to replace ploymer sphere, and no extra precious additives like n-octadecyltrimethoxysilane(C18TMS). Supported phosphotungstic acid(PTA) catalysts on SHMS(PTA/SHMS) and on previously reported spherical mesoporous silica(PTA/SMS) with 25 wt% of PTA loading were prepared and employed as solid acid catalysts for diverse reactions. Transmission electron microscopy(TEM),N_2 adsorption-desorption, X-ray diffraction(XRD), and NH_3 temperatureprogrammed desorption(NH_3-TPD) techniques were employed to characterize the nature of carriers and supported PTA catalysts for revealing the structure-performance relationship. The developed PTA/SHMS catalyst demonstrates much higher catalytic activity than PTA/SMS for diverse reactions including alkenylation, esterification, alkylation, and benzylation, ascribed to the strengthened mass transfer and enlarged exposure degree of acidic sites to reactants those resulting from unique hollow and mesoporous morphology. Moreover, PTA/SHMS catalyst also exhibits outstanding catalytic performance for the diverse a-arylstyrenes via solid acid-mediated alkenylation. PTA/SHMS could be considered as a practical solid acid catalyst for diverse transformations.

Silicotungstic acid-derived WO_(3) composited with ZrO_(2) supported on SBA-15 as a highly efficient mesoporous solid acid catalyst for the alkenylation of p-xylene with phenylacetylene

Highly dispersed silicotungstic acid-derived WO_(3) composited with ZrO_(2) supported on SBA-_(15) (WZ/SBA-_(15)) as an ordered mesoporous solid acid catalyst was prepared via a facile incipient wetness impregnation (IWI) method that active ingredients, ZrO_(2) and WO_(3), were impregnated into the channels of SBA-_(15) simultaneously with a subsequent calcination process. The relationship between catalyst nature and performance was explored by high resolution transmission electron microscopy (HRTEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), FT-IR, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), N_(2) adsorption-desorption, NH_(3) temperature-programmed desorption (NH_(3)-TPD), and FT-IR of pyridine adsorption (Py-IR) characterization techniques. The catalytic performance of W_(12)Z_(15)/SBA-_(15) is not only greater than that of single component solid acid catalysts, WO_(3)/SBA-_(15) and ZrO_(2)/SBA-_(15), but also W_(12)/Z_(15)/SBA-_(15) prepared by impregnating active ingredients, ZrO_(2) and WO_(3), into SBA-_(15) in sequence. The outstanding performance of W_(12)Z_(15)/SBA-_(15) is derived from the strong interaction between ZrO_(2) and WO_(3), which results in more acid sites, and relatively high specific surface area, large pore volume, and ordered mesoporous structure of SBA-_(15). The characterization and reaction results clearly demonstrate that the synergy of ZrO_(2) and WO_(3) has a clear boost for the alkenylation. The optimized W_(12)Z_(15)/SBA-_(15)-500 achieves a 99.4% conversion of phenylacetylene and a 92.3% selectivity of main product α-arylstyrene for the alkenylation of p-xylene with phenylacetylene, with very low level of oligomers producing at the same time. Moreover, W_(12)Z_(15)/SBA-_(15)-500 shows excellent catalytic stability and regeneration. Therefore, W_(12)Z_(15)/SBA-_(15)-500 is a promising solid acid catalyst for the alkenylation.

TMSCI Promoted Direct sp3 C-H Alkenylation to Construct （E）-2-Styryl-tetrahydrobenzo[d]thiazoles

A high-efficient and stereo-specific approach for the preparation of biologically important （E）-2-styryl-tetra- hydrobenzo[d]thiazoles has been developed via TMSC1 promoted direct sp3 C-H alkenylation of 2-methyl-5,6-di- hydrobenzo[d]thiazol-7（4H）-one under metal-free conditions. Seventeen target compounds were synthesized in ex- cellent yields of 82%--98% under the optimal conditions of 300 mol% TMSCI at 110℃ for 2 h, and their chemical structures were elucidated by IR, NMR, ESI-MS, elemental analyses and X-ray crystallography analysis. A plausible mechanism was also proposed, and this method provided a good functional group conversion for the sp3 C-H substrates.

Aromatic and olefinic C–H alkenylation by catalysis with spirocyclic NHC Ru(Ⅳ) pincer complex

Catalyst innovation lies at the heart of transition-metal-catalyzed reaction development. In this article, we have explored the C(sp2)–H alkenylation activity with novel spirocyclic N-heterocyclic carbene(NHC)-based cyclometalated ruthenium pincer catalyst system, SNRu-X. After screening catalyst and condition, a high valent Ru(Ⅳ) dioxide(X = O_(2)) species has demonstrated superior reactivity in the catalytic alkenylation of aromatic and olefinic C–H bonds with unactivated alkenyl bromides and triflates. This reaction has achieved the easy construction of a wide range of(hetero)aromatic alkenes and dienes, in good to excellent yields with exclusive selectivity. Preliminary mechanistic studies indicate that this reaction may proceed through a single electron transfer(SET) triggered oxidative addition, by doing so, providing valuable complementary to classical alkenylation reactions that are dependent on activated alkenyl precursors.

Chemo-and Enantioselective Arylation and Alkenylation of Aldehydes Enabled by Nickel/N-Heterocyclic Carbene Catalysis

Herein,we report the first highly enantioselective Ni-catalyzed arylation and alkenylation of simple aldehydes using readily available and stable organoboronic esters.This protocol provides various chiral secondary alcohols in high yields and enantioselectivities(up to 97% ee)with a broad scope of substrates,functional groups,and heterocycles.The use of a bulky N-heterocyclic carbene(NHC)ligand for nickel catalyst is the key to high enantiocontrol.The competitive Ni-catalyzed transformations,including Tishchenko reaction,dehydrogenation/hydrogenation reaction,and Suzuki-Miyaura couplings,are avoided.The excellent chemoselectivity is likely due to the application of mild base CsF and η^(2)-coordination of aldehydes with nickel.

Construction of chiral 3-alkenyl-3-substituted oxindoles by stereoselective direct alkenylation of isatin derivatives and 3-vinylindoles

An efficient asymmetric alkenylation between 3-vinylindoles and isatin derivatives was developed under catalysis of a chiral copper complex.A series of optically active 3-alkenyl-3-substituted oxindoles were obtained in excellent yields and stereoselectivities.The reaction mechanism was proposed and supported by DFT calculation.

Rapid alkenylation of quinoxalin-2(1H)-ones enabled by the sequential Mannich-type reaction and solar photocatalysis

Herein,a rapid alkenylation of quinoxalin-2(1H)-ones enabled by a combination of Mannich-type reaction and solar photocatalysis is demonstrated.A wide range of functional groups are compatible,affording the corresponding products in moderate-to-good yields.Control experiments illustrate that the in situ generated^(1)O_(2)plays a central role in this reaction.This green and efficient strategy provides a practical solution for the synthesis of potentially bioactive compounds that containing a 3,4-dihydroquinoxalin-2(1H)-one structure.

Rhodium-Catalyzed Direct C-H Alkenylation of Indoles with Alkenyl Borates

Main observation and conclusion A new Rh(Ⅲ)-catalyzed direct C—H alkenylation of 2,3-unsubstitued indoles with alkenyl borates through C—H activation followed by transmetallation was described.This protocol provides an efficient method for the synthesis of terminal C2-alkenylindoles under mild conditions,and also shows broad substrate scope and high functional group tolerance with respect to both components.Furthermore,the C2-alkenylated indole can be easily transformed into carboline derivative,which is an important polycyclic indole moiety in natural products and drug molecules.

Nanoparticle-stabilized Alkenyl Succinic Anhydride(ASA)Emulsions:A Review

Alkenyl succinic anhydride(ASA) is a popular paper-sizing agent that is generally added to papermaking systems as an aqueous emulsion. Herein, we reviewed the recent work focusing on ASA emulsions stabilized by solid particles. Solid particle-stabilized ASA emulsions generally possess high ASA content and exhibit good sizing performance. The particles that have been used to stabilize ASA emulsions typically include montmorillonite, laponite, alumina, TiO_2, Fe_3O_4, polyaluminum sulfate(PAS), and cellulose nanocrystals(CNCs). Montmorillonite is the first extensively studied particle stabilizer for ASA emulsions. Laponite is undoubtedly the most competent particle stabilizer for preparing ASA emulsions with high sizing efficiency. Montmorillonite and laponite can be used individually as stabilizers after modification or as co-stabilizers with other particles or polymers. TiO_2, alumina, PAS, and CNCs are commonly used as stabilizers either individually or with other particles.

(Z)-a-Selanyl Alkenyl Grignard Reagents as Convenient Precursors for Stereoselective Synthesis of Trisubstituted Alkenes

Z)-a-Selanyl alkenyl Grignard reagents 2 were prepared conveniently by treatment of a-bromovinylselenides 1 with magnesium filings in THF. Intermediates 2 were reacted with alkyl iodides in the presence of CuI or Pd(PPh3)4 to afford (Z)-1,2-disubstituted vinylselenides 3, which were cross-coupled with Grignard reagents in the presence of (PPh3)2NiCl2 to give trisubstituted alkenes 4 stereoselectively in good yields.

Co/Fe Dual Catalysis for Sequential Hydrosilylation-Isomerization:Access to Trisubstituted(E)-Alkenyl Silanes from Terminal Alkynes

By rational modification of electronic and steric properties of pincer ligands,a Co/Fe dual catalyst system is developed for one-pot sequential Markovnikov alkyne hydrosilylation and stereoselective alkene isomerization.The protocol provides an atom-economical and efficient approach to trisubstituted(E)-alkenyl silanes from widely accessible terminal alkynes with high regio-and stereoselectivities under mild conditions.The utility of this reaction was demonstrated by gram-scale synthesis and derivatization of bioactive molecules.The radical clock and trapping experiments indicated that radical pathway might be operative in the alkene isomerization step.

Chemoselective and Living/Controlled Polymerization of Alkenyl Methacrylates by the Phosphonium Ylide/Organoaluminum Lewis Pairs

Chemoselective,living/controlled polymerizations of allyl methacrylate(AMA) and vinyl methacrylate(VMA) with/without methyl methacrylate(MMA) by using the phosphonium ylide/organoaluminum based Lewis pairs(LPs) have been realized.The P-ylide-2/AIMe(BHT)_(2)(Pylide-2=Ph_(3)P=CHMe and BHT=2,6-iBu_(2)-4-MeC_(6)H_(2)O) was demonstrated to be superior by which homopolymers PAMAs(M_(n)=27.6-111.5kg/mol and ■=1.14-1.25) and PVMAs(M_(n)=28.4-78.4 kg/mol and ■=1.12-1.18) and block copolymers PMMA-b-PAMA,PAMA-b-PVMA,PAMA-bPMMA,PMMA-b-PAMA-b-PMMA,PAMA-b-PMMA-b-PAMA,and PAMA-b-PVMA-b-PAMA were synthesized.In the polymerizations,all of the monomers were reacted by the conjugated ester vinyl groups leaving intactly the nonconjugated acryloxy groups.The pendant acryloxy groups attached to the main chain enable further to post-functionalization by the AIBN-induced radical "thiol-ene" reaction using PhCH_(2)SH.The thiolether side group-containing polymers PAMA-SCH_(2)Ph and PAMA-SCH_(2)Ph-b-PMMA-b-PAMA-SCH_(2)Ph were thus prepared.

Asymmetric Two-Component Alkenyl Catellani Reaction for the Construction of C—N Axial Chirality

Herein,we report an asymmetric two-component alkenyl Catellani reaction for the construction of C—N axial chirality through a palladium/chiral norbornene cooperative catalysis and an axial-to-axial chirality transfer process.Various partially aromatic iodinated 2-pyridones,quinolones,coumarin and uracil substrates react with 2,6-disubstituted aryl bromides with a tethered amide group,to afford a wide variety of polycyclic C—N atropisomers(38 examples,up to 97%e.e.).The obtained C—N axial chirality originates from the preformed transient C—C axial chirality with high fidelity.The synthetic utility of this chemistry is demonstrated by facile prepa-ration of complex quinoline and pyridine based C—N atropisomers through a N-deprotection and aromatization sequence.In addi-tion,a remote axial-to-central diastereoinduction process dictated by C—N axial chirality is observed with excellent diastereocontrol.

Rapid Access to Polysubstituted Tetrahydrocarbazol-4-ones via Sequential Selective C—H Functionalization from N-Nitrosoanilines

Comprehensive Summary Herein,we have developed a strategy of Rh(III)-catalyzed C—H activation of N-nitrosoanilines and iodonium ylides to construct novel tetralydrocarbzol-4-one scaffolds,which provided valuable templates for sequential C—H functionalization such as alkylation,alkenylation,amidation and(hetero)arylation at C^(5)-position of tetralydrocarbzol-4-one with different coupling partners.Gram-scale synthesis and further transformations of tetralydrocarbzol-4-one derivatives to Ondansetron and its analogues demonstrated the utility of this protocol,which enabled the concise and diverse construction of biologically active molecules.

Lewis Acid Enables Ketone Phosphorylation:Synthesis of Alkenyl Phosphonates

Main observation and conclusion An efficient Lewis acid enabled ketones phosphonylation to synthesize vinylphosphonates has been developed.This method relays on ketone hydrophosphonylation/α-hydroxy phosphonates unimolecular elimination(E1)dehydration cascade reaction sequence.