Rhodium-Catalyzed Alkyne Research Articles

Asymmetric synthesis, structures, and chiroptical properties of helical cycloparaphenylenes.

Planar chiral carbon nanorings and nanobelts (CNRs and CNBs), the sidewall segment molecules of chiral-type carbon nanotubes (CNTs), have attracted attention owing to their characteristic chiroptical properties. From the appropriate CNTs, axially or planar chiral CNRs and CNBs have been designed and synthesized, but multiply helical sidewall segments were almost unexplored due to the difficulty in simultaneous control of multiple chiralities. In this article, we have succeeded in the perfectly diastereo- and enantiocontrolled catalytic synthesis of a cycloparaphenylene with four helical and two planar chiralities showing good chiroptical responses as chiral organic molecules. The perfectly stereocontrolled multiply helical structure was confirmed by a single-crystal X-ray diffraction analysis. The experimental and theoretical studies established the importance of the highly symmetric multiply helical structure in the cylindrical axis in obtaining good chiroptical responses.

Enantioselective Synthesis of Planar Chiral Zigzag-Type Cyclophenylene Belts by Rhodium-Catalyzed Alkyne Cyclotrimerization.

Planar chiral zigzag-type [8]- and [12]cyclophenylene (CP) belts have been synthesized in good yields with high ee values of 98% and 83%, respectively, by the rhodium-catalyzed enantioselective intramolecular sequential cyclotrimerizations of the corresponding cyclic polyynes. The observed high enantioselectivity arises from the regioselective formation of a rhodacycle intermediate from an unsymmetric triyne unit. The X-ray crystal structural analysis of the racemic planar chiral zigzag-type [8]CP belt revealed that the uneven molecules mesh with each other to form a one-dimensional columnar packing structure, in which one column contains single enantiomers, giving two types of chiral columns [(S)- and (R)-form columns] arranged alternately. The ring strain of the zigzag-type [8]CP belt was smaller than that of the armchair-type [8]CPP belt despite its smaller ring size, due to the presence of the strain-relieving m-terphenyl moieties. The effect of the number of the benzene rings of the zigzag-type CP belts on absorption and emission peaks was small due to interruption of π-conjugation at the m-phenylene moieties. However, the bending effect on the absolute fluorescence quantum yield as well as absorption and emission peaks was significant. Concerning chiroptical properties, the modest anisotropy dissymmetry factors of ECD and CPL were observed in the [8]CP belt.

Synthesis of Belt- and Möbius-Shaped Cycloparaphenylenes by Rhodium-Catalyzed Alkyne Cyclotrimerization.

A belt-shaped [8]cycloparaphenylene (CPP) and an enantioenriched Möbius-shaped [10]CPP have been synthesized by high-yielding rhodium-catalyzed intramolecular cyclotrimerizations of a cyclic dodecayne and a pentadecayne, respectively. This Möbius-shaped [10]CPP possesses stable chirality and isolated with high enantiomeric purity. It is evident from the reaction Gibbs energy calculation that the above irreversible cyclotrimerizations are highly exothermic; therefore establishing that the intramolecular alkyne cyclotrimerization is a powerful route to strained cyclic molecular strips.

Examining the Factors That Govern the Regioselectivity in Rhodium-Catalyzed Alkyne Cyclotrimerization

The electronic and steric factors that favor the formation of 1,2,4- and 1,3,5-regioisomers in the intermolecular [2 + 2 + 2] cyclotrimerization of terminal alkynes are not well understood. In this...

Synthesis of Allahabadolactone A

A synthesis of allahabadolactone A is described employing diastereoselective Diels-Alder and selenocyclization reactions, starting from (R)-citronellal and propylene oxide. The Diels-Alder substrate is built up in an efficient manner by rhodium-catalyzed alkyne hydroboration and palladium-catalyzed coupling reactions of E-1,2-dichloroethene. It is observed that the Diels-Alder reaction only displays high diastereoselectivity when the diene bears an additional alkene substituent but not an alkyne substituent.

Enantioselective Three-Component Assembly of β'-Aryl Enones Using a Rhodium-Catalyzed Alkyne Hydroacylation/Aryl Boronic Acid Conjugate Addition Sequence.

Rhodium-catalyzed alkyne hydroacylation using alkyl β-S-aldehydes, enantioselective rhodium-catalyzed aryl boronic acid conjugate addition, and sulfide elimination are combined in sequence to provide β'-aryl enones. The reaction sequence is efficient and delivers highly functionalized products with excellent levels of enantiocontrol. Good variation of the three reaction components is demonstrated. The sequence corresponds to the formal regio- and enantioselective monoconjugate addition of aryl boronic acids to dienones.

Two-Component Assembly of Thiochroman-4-ones and Tetrahydrothiopyran-4-ones Using a Rhodium-Catalyzed Alkyne Hydroacylation/Thio-Conjugate-Addition Sequence.

β'-Thio-substituted-enones, assembled from the combination of β-tert-butylthio-substituted aldehydes and alkynes, using rhodium catalysis, are shown to smoothly undergo in situ intramolecular S-conjugate addition to deliver a range of S-heterocycles in a one-pot process. Aryl, alkenyl, and alkyl aldehydes can all be employed, to provide thiochroman-4-ones, hexahydro-4H-thiochromen-4-ones, and tetrahydrothiopyran-4-ones, respectively. A variety of in situ oxidations are also performed, allowing access to S,S-dioxide derivatives, as well as unsaturated variants.

Correction to "Diversely Substituted Quinolines via Rhodium-Catalyzed Alkyne Hydroacylation".

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to “Diversely Substituted Quinolines via Rhodium-Catalyzed Alkyne Hydroacylation”James D. Neuhaus, Sarah M. Morrow, Michael Brunavs, and Michael C. Willis*Cite this: Org. Lett. 2016, 18, 10, 2519Publication Date (Web):April 29, 2016Publication History Received26 April 2016Published online29 April 2016Published inissue 20 May 2016https://doi.org/10.1021/acs.orglett.6b01218Copyright © 2016 American Chemical SocietyRIGHTS & PERMISSIONSACS AuthorChoicewith CC-BYlicenseArticle Views1159Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (177 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Diversely Substituted Quinolines via Rhodium-Catalyzed Alkyne Hydroacylation.

The Rh-catalyzed hydroacylative union of aldehydes and o-alkynyl anilines leads to 2-aminophenyl enones, and onward to substituted quinolines. The mild reaction conditions employed in this chemistry result in a process that displays broad functional group tolerance, allowing the preparation of diversely substituted quinolines in high yields. Extension to the use of o-alkynyl nitro arenes as substrates leads to 2-nitrochalcones, from which both quinolines and quinoline N-oxides can be accessed.

A detailed kinetic analysis of rhodium-catalyzed alkyne hydrogenation

Continuous monitoring using electrospray ionisation mass spectrometry (ESI-MS) shows that Wilkinson's catalyst hydrogenates a charge-tagged alkyne to the corresponding alkene, and at only a marginally slower rate, to the alkane. No rhodium-containing intermediates were observed during the reaction, consistent with the established mechanism which points at the initial dissociation of triphenylphosphine from Rh(PPh₃)₃Cl as being the key step in the reaction. A numerical model was constructed that the closely matched the experimental data, and correctly predicted the response of the reaction to the addition of excess PPh₃.

Rhodium-Catalyzed Alkyne Carbothiolations

Rhodium-Catalyzed Alkyne Carbothiolations

Aryl Methyl Sulfides as Substrates for Rhodium-Catalyzed Alkyne Carbothiolation: Arene Functionalization with Activating Group Recycling

A Rh(I)-catalyzed method for the efficient functionalization of arenes is reported. Aryl methyl sulfides are combined with terminal alkynes to deliver products of carbothiolation. The overall process results in reincorporation of the original arene functional group, a methyl sulfide, into the products as an alkenyl sulfide. The carbothiolation process can be combined with an initial Rh(I)-catalyzed alkene or alkyne hydroacylation reaction in three-component cascade sequences. The utility of the alkenyl sulfide products is also demonstrated in simple carbo- and heterocycle-forming processes. We also provide mechanistic evidence for the course of this new process.

Aggregation‐Induced Emission in a Hyperbranched Poly(silylenevinylene) and Superamplification in Its Emission Quenching by Explosives

A silicon-containing hyperbranched polymer (hb-P1/2) with σ*-π* conjugation was prepared in a good yield and high molecular weight by rhodium-catalyzed alkyne polyhydrosilylation of 1,2-bis(4-ethynylphenyl)-1,2-diphenylethene (1) with tris(4-dimethylsilylphenyl)amine (2). The polymer was thermally stable, losing merely 5% of its weight when heated to ≈445 °C. Whereas hb-P1/2 was weakly luminescent when molecularly dissolved, it became highly emissive when supramolecularly aggregated, showing an aggregation-induced emission (AIE) phenomenon. A superamplification effect was observed when the AIE nanoaggregates were used as fluorescent chemosensor for explosive detection: the quenching efficiency was greatly increased in a nonlinear fashion with increasing quencher concentration.

Synthesis of 1,1-Disubstituted Alkyl Vinyl Sulfides via Rhodium-Catalyzed Alkyne Hydrothiolation: Scope and Limitations

Described herein are the scope and limitations using Tp*Rh(PPh(3))(2) as a catalyst for alkyne hydrothiolation with alkyl thiols. In general, catalytic hydrothiolation proceeds in high yields and with high regioselectivity for a wide range of alkynes and thiols. A variety of functional groups were well-tolerated, including nitriles, amines, halogens, ethers, esters and silanes, although strongly coordinating groups were found to be incompatible with hydrothiolation. Both sterically encumbered alkynes and thiols were successful in hydrothiolation. Electron rich alkynes react more rapidly than electron deficient alkynes. Overall, this hydrothiolation protocol provides convenient access to a variety of functionalized branched alkyl vinyl sulfides.

Triptycenediols by Rhodium-Catalyzed [2 + 2 + 2] Cycloaddition

An efficient, modular synthesis of triptycene derivatives is presented, in which the triptycene ring system is constructed from readily available anthraquinone and alkyne starting materials. A rhodium-catalyzed alkyne cyclotrimerization reaction serves as the key step in this new method for the preparation of these useful unnatural products.

Enantioselective Synthesis of Planar-Chiral Metacyclophanes through Rhodium-Catalyzed Alkyne Cyclotrimerization

We have achieved the first catalytic enantioselective synthesis of planar-chiral metacyclophanes by means of cationic rhodium(I)/(R)-H8-BINAP complex-catalyzed alkyne cyclotrimerization. This reaction represents a versatile new method for the preparation of planar-chiral [7]−[10]metacyclophanes.

Rhodium-Catalyzed Alkyne Hydrothiolation with Aromatic and Aliphatic Thiols

Alkyne hydrothiolation is a potentially attractive method for the formation of vinyl sulfides, which are valuable synthetic intermediates. Known methods for hydrothiolation using alkyl thiols are quite limited. We report herein that Tp*Rh(PPh3)2 (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate) is a highly active catalyst for alkyne hydrothiolation with alkyl and aryl thiols. Hydrothiolation using alkyl thiols proceeds with excellent regioselectivity, providing convenient access to branched alkyl vinyl sulfides, which are difficult to synthesize by other means. A mixture of regioisomers is obtained when using aryl thiols, with the branched isomer as the major product, opposite that reported for other Rh complexes.

Synthesis of monodisperse oligo-p-phenylenes via rhodium-catalyzed alkyne cyclotrimerization.

[structure: see text] A novel synthesis of monodisperse oligo-p-phenylenes is described that features alkyne cyclotrimerization of ether-linked p-dialkynylarenes. This route introduces solubilizing dihydrofuran and alcohol functional groups that may improve processing of the corresponding polymeric p-phenylene materials.