Alkenyl Aryl Research Articles

Synthesis of Sulfilimines Enabled by Copper-Catalyzed S-Arylation of Sulfenamides.

Herein, an unprecedented synthetic route to sulfilimines via a copper-catalyzed Chan-Lam-type coupling of sulfenamides is presented. A key to success in this novel transformation is the chemoselective S-arylation of S(II) sulfenamides to form S(IV) sulfilimines, overriding the competitive, and more thermodynamically favored, C-N bond formation that does not require a change in the sulfur oxidation state. Computations reveal that the selectivity arises from a selective transmetallation event where bidentate sulfenamide coordination through the sulfur and oxygen atoms favors the S-arylation pathway. The mild and environmentally benign catalytic conditions enable broad functional group compatibility, allowing a variety of diaryl or alkyl aryl sulfilimines to be efficiently prepared. The Chan-Lam coupling procedure could also tolerate alkenylboronic acids as coupling partners to afford alkenyl aryl sulfilimines, a class of scaffolds that cannot be directly synthesized via conventional imination strategies. The benzoyl-protecting groups could be conveniently removed from the product, which, in turn, could be readily transformed into several S(IV) and S(VI) derivatives.

Recent Developments in the Electroreductive Functionalization of Carbon–Halogen Bonds

AbstractElectrochemical organic transformations have witnessed significant progress over the past decades owing to their idiosyncratic redox nature. Electrochemistry is globally acknowledged for its sustainability and environmental friendliness, whilst several well-known redox processes are available that do not generate chemical waste or toxic by-products. Apart from this, electrochemistry has adequate potential to steer numerous non-spontaneous reactions, such as cross-coupling, C–C bond cleavage, radical generation, directed C–H functionalization, etc., in a straightforward manner. Beyond electrochemical oxidation reactions, electrochemical reductive transformations have also been enriched in the last few years. Electrochemical reduction can be facilitated by using different strategies, for example, by using a sacrificial electrode or a sacrificial reagent, or can be accomplished in a divided cell. In this short review, different methods for the functionalization of C–halogen bonds, including detailed mechanistic approaches, are discussed.1 Introduction2 Different Strategies for Electrochemical Reduction3 Functionalization of Carbon–Halogen Bonds through Electrochemical Reduction3.1 E lectroreductive Hydrodehalogenation3.2 Electroreductive C–C Coupling of Organohalides3.2.1 Aryl–Aryl C–C Coupling3.2.2 Aryl–Alkenyl C–C Coupling3.2.3 Aryl–Alkyl C–C Coupling3.2.4 Alkyl–Alkenyl C–C Coupling3.2.5 Alkyl–Alkyl C–C Coupling3.3 Electroreductive Coupling of Organohalides with Carbonyls (C=O)3.4 Electroreductive Coupling of Organohalides with Organoboranes4 Conclusion

Radical Aryl Migration from Boron to Carbon.

Radical aryl migration reactions represent a unique type of organic transformations that involve the intramolecular migration of an aryl group from a carbon or heteroatom to a C- or heteroatom-centered radical through a spirocyclic intermediate. Various elements, including N, O, Si, P, S, Sn, Ge, and Se, have been reported to participate in radical aryl migrations. However, radical aryl migration from a boron center has not been reported to date. In this communication, radical 1,5-aryl migration from boron to carbon in aryl boronate complexes is presented. C-radicals readily generated through radical addition onto alkenyl aryl boronate complexes are shown to engage in 1,5-aryl migration reactions to provide 4-aryl-alkylboronic esters. As boronate complexes can be generated in situ by the reaction of alkenylboronic acid esters with aryl lithium reagents, the aryl moiety is readily varied, providing access to a series of arylated products starting from the same alkenylboronic acid ester via divergent chemistry. Reactions proceed with high diastereoselectivity under mild conditions, and also the analogous 1,4-aryl shifts are feasible. The suggested mechanism is supported by DFT calculations.

Computational insights into electrochemical cross‐coupling of quaternary borate salts

AbstractCross‐coupling reactions for C–C bond formation represent a cornerstone of organic synthesis. In most cases, they make use of transition metals, which has several downsides. Recently, metal‐free alternatives relying on electrochemistry have gained interest. One example of such a reaction is the oxidation of tetraorganoborate salts that initiates aryl–aryl and aryl–alkenyl couplings with promising selectivities. This work investigates the mechanism of this reaction computationally using density functional and coupled‐cluster theory. The calculations reveal a distinct difference between aryl–alkenyl and aryl–aryl couplings: While C–C bond formation occurs irreversibly and without an energy barrier if an alkenyl residue is involved, many intermediates can be identified in aryl–aryl couplings. In the latter case, intramolecular transitions between reaction paths leading to different products are possible. Based on the energy differences between these intermediates, a kinetic model to estimate product distributions for aryl–aryl couplings is developed.

CuI catalyzed-novel one-pot synthesis of aryl alkenyl thioethers through Ullmann-type coupling reactions using carbon disulfide as a sulfur surrogate in the presence of nitroalkanes and aryl iodides

A mild, general and efficient copper-catalyzed system for C-S bond formation is developed. With CuI as catalyst and l-Proline as ligand, the S-arylation of nitroalkane-CS2 adducts with aryl iodides were performed under mild conditions to give the corresponding products in good to excellent yields.

The Reactions of Aryl Tin(II) Hydrides {AriPr6Sn(μ-H)}2 (AriPr6 = C6H3-2,6-(C6H2-2,4,6-iPr3)2) and {AriPr4Sn(μ-H)}2 (AriPr4 = C6H3-2,6-(C6H3-2,6-iPr2)2) with Aryl Alkynes: Substituent Dependent Structural Isomers

The reactions of the aryl tin(II) hydrides {AriPr6Sn(μ-H)}2 (AriPr6 = C6H3-2,6-(C6H2-2,4,6-iPr3)2) and {AriPr4Sn(μ-H)}2 (AriPr4 = C6H3-2,6-(C6H3-2,6-iPr2)2) with aryl alkynes were investigated. Reaction of {AriPr6Sn(μ-H)}2 and {AriPr4Sn(μ-H)}2 with 2 equiv of diphenyl acetylene, PhCCPh, afforded the aryl alkenyl stannylenes AriPr6SnC(Ph)C(H)Ph (1) and AriPr4SnC(Ph)C(H)Ph (2). In contrast, the analogous reactions of {AriPr6Sn(μ-H)}2 with 2 equiv of phenyl acetylene, HCCPh, afforded a high yield of the cis-1,2 addition product AriPr6(H)SnC(H)C(Ph)Sn(H)AriPr6 (3), which has a four-membered Sn2C2 core structure comprised of two Sn–Sn bonded Sn(H)AriPr6 units bridged by a −C(H)═C(Ph)– moiety. The corresponding reaction of the less bulky hydride {AriPr4Sn(μ-H)}2 with 2 equiv of phenyl acetylene leads to AriPr4SnC(H)C(Ph)Sn(H)2AriPr4 (4) which unlike 3 has no Sn–Sn bonding. Instead, the tin atoms are connected solely by a −C(H)═C(Ph)– moiety. Each tin atom carries a AriPr4 substituent but one is also substituted...

Dehydrative Nazarov-type electrocyclizations of alkenyl (hetero)aryl carbinols via calcium catalysis: Access to cyclopenta[b]thiophenes and indene derivatives

A general approach to the understudied cyclopenta[b]thiophenes is reported. The products were directly generated from calcium-catalyzed, dehydrative, Nazarov-type electrocyclizations of alkenyl thienyl carbinols in up to 82% yield. The thienyl carbinols demonstrated good tolerance for aryl and heteroaryl substituents on the alkene. Aryl carbinols were also amenable to the calcium-catalyzed conditions and afforded indene derivatives in good yields. In most cases, the reaction was selective for the thermodynamic alkene isomer; however, substituent effects played a role in determining product outcomes. Mechanistically, the calcium catalyst initiated formation of alkenyl (hetero)aryl carbinyl cations which subsequently underwent a 4π electrocyclization and elimination that is reminiscent of the Nazarov reaction. This transformation is significant for two main reasons: 1) it represents one of the only examples of catalysis for dehydrative, Nazarov-type electrocyclizations in which thiophene was compatible; 2) it allowed for the direct formation of cyclopenta[b]thiophenes while circumventing the need for cyclopenta[b]thiophenones as precursors.

Isothiourea-Catalysed Acylative Kinetic Resolution of Aryl-Alkenyl (sp2 vs. sp2 ) Substituted Secondary Alcohols.

The non‐enzymatic acylative kinetic resolution of challenging aryl–alkenyl (sp2 vs. sp2) substituted secondary alcohols is described, with effective enantiodiscrimination achieved using the isothiourea organocatalyst HyperBTM (1 mol %) and isobutyric anhydride. The kinetic resolution of a wide range of aryl–alkenyl substituted alcohols has been evaluated, with either electron‐rich or naphthyl aryl substituents in combination with an unsubstituted vinyl substituent providing the highest selectivity (S=2–1980). The use of this protocol for the gram‐scale (2.5 g) kinetic resolution of a model aryl–vinyl (sp2 vs. sp2) substituted secondary alcohol is demonstrated, giving access to >1 g of each of the product enantiomers both in 99:1 e.r.

ChemInform Abstract: Copper(I)‐Catalyzed Diastereoselective Borylative exo‐Cyclization of Alkenyl Aryl Ketones.

Copper(I)-catalyzed diastereoselective borylative exo-cyclization of alkenyl ketones with bis(pinacolato)diboron is reported. The reaction of alkenyl aryl ketones under a CuCl/Xantphos catalyst system provides four- or five-membered-ring syn-2-(borylmethyl)cycloalkanol derivatives in good yields with high syn selectivities. The utility of this method is demonstrated by further transformations of the cyclic products.

Copper(I)-Catalyzed Diastereoselective Borylative Exo-Cyclization of Alkenyl Aryl Ketones

Copper(I)-catalyzed diastereoselective borylative <i>exo</i>-cyclization of alkenyl ketones with bis(pinacolato)diboron is reported. The reaction of alkenyl aryl ketones under a CuCl/Xantphos catalyst system provides four- or five-membered-ring <i>syn</i>-2-(borylmethyl)cycloalkanol derivatives in good yields with high <i>syn</i> selectivities. The utility of this method is demonstrated by further transformations of the cyclic products.

Breaking and Making of Olefins Simultaneously Using Ozonolysis: Application to the Synthesis of Useful Building Blocks and Macrocyclic Core of Solomonamides

A simple and practical one-pot, two-directional approach to access olefinic esters through simultaneous breaking and making of olefins using ozonolysis of alkenyl aryl selenides is disclosed. The scope of the method with a variety of examples is demonstrated, and the end products obtained here are useful building blocks. As a direct application of the present method, the macrocyclic core of potent anti-inflammatory natural cyclic peptides, solomonamides, is synthesized.

ChemInform Abstract: Unmasked Acyl Anion Equivalent from Acid Chloride with Indium: Reversed‐Polarity Synthesis of Unsymmetric Aryl Aryl and Alkenyl Aryl Ketone Through Palladium‐Catalyzed Cross‐Coupling Reaction.

A reversed-polarity synthetic method of a range of unsymmetric aryl aryl and alkenyl aryl ketones has been developed through Pd-catalyzed cross-coupling reaction of acylindium reagents generated in situ from easily available acid chlorides and indium with various electrophiles such as aryl iodide and triflate and alkenyl triflate.

Unmasked Acyl Anion Equivalent from Acid Chloride with Indium: Reversed-Polarity Synthesis of Unsymmetric Aryl Aryl and Alkenyl Aryl Ketone through Palladium-Catalyzed Cross-Coupling Reaction

A reversed-polarity synthetic method of a range of unsymmetric aryl aryl and alkenyl aryl ketones has been developed through Pd-catalyzed cross-coupling reaction of acylindium reagents generated in situ from easily available acid chlorides and indium with various electrophiles such as aryl iodide and triflate and alkenyl triflate.

Preparation and Characterization of Alkenyl Aryl Tetrafluoro‐λ6‐sulfanes

Substituted alkenyl aryl tetrafluoro-λ(6) -sulfanes have been prepared by the direct addition of readily accessible chlorotetrafluorosulfanyl arenes to primary alkynes. Substitution of an apical fluorine of the pentafluorosulfanyl group enables modulation of the reactivity of this little explored functional group while at the same time facilitating the direct investigation of aryl substituent effects on the aryl tetrafluorosulfanyl-substituted products.

Preparation and Characterization of Alkenyl Aryl Tetrafluoro‐λ6‐sulfanes

AbstractSubstituted alkenyl aryl tetrafluoro‐λ6‐sulfanes have been prepared by the direct addition of readily accessible chlorotetrafluorosulfanyl arenes to primary alkynes. Substitution of an apical fluorine of the pentafluorosulfanyl group enables modulation of the reactivity of this little explored functional group while at the same time facilitating the direct investigation of aryl substituent effects on the aryl tetrafluorosulfanyl‐substituted products.

A general and green procedure for the synthesis of organochalcogenides by CuFe2O4nanoparticle catalysed coupling of organoboronic acids and dichalcogenides in PEG-400

A general and efficient procedure has been developed for the synthesis of organochalcogenides (selenides and tellurides) by a simple reaction of organoboronic acids and dichalcogenides catalysed by CuFe2O4 nanoparticles in PEG-400 without any ligand. This protocol offers the scope for access to a wide spectrum of chalcogenides including diaryl, aryl–heteroaryl, aryl–styrenyl, aryl–alkenyl, aryl–allyl, aryl–alkyl and aryl–alkynyl versions. The catalyst is magnetically separable and recyclable eight times without any loss of appreciable catalytic activity. The products are obtained in high purities after evaporation of solvent followed by filtration column chromatography.

ChemInform Abstract: Enantioselective 1,4‐Conjugate Addition of Diethylzinc to (E)‐Alkenyl Aryl Ketones Catalyzed by Cu/DiPPAM Complex.

ChemInform Abstract: Enantioselective 1,4‐Conjugate Addition of Diethylzinc to (E)‐Alkenyl Aryl Ketones Catalyzed by Cu/DiPPAM Complex.

Pd-catalyzed cross-coupling reactions exhibiting catalyst turnover numbers (TONs) exceeding one million

Pd-catalyzed cross-coupling giving aryl–aryl, alkenyl–aryl, aryl–alkenyl, alkynyl–aryl, and alkynyl–alkenyl products exhibited ultra-high turnover numbers (TONs) of 0.7×10~0.69×10 by using organozincs generated in situ by treatment of the corresponding organolithiums with dry ZnBr2. Additionally, the hydrozirconation–Pd-catalyzed cross-coupling tandem processes via treatment of 1-alkynes with Bu2AlH-ZrCp2Cl2 followed by selective (≥98%) alkenyl–alkenyl coupling with either (E)or (Z)-ethyl 3-bromoacrylate exhibited high TONs of 0.9×10~0.81×10. Furthermore, Pd-catalyzed cross-coupling of 2-thienylzinc bromide and 1iodo-4-nitrobenzene also showed a high TON of 0.87×10.

ChemInform Abstract: Efficient Aziridination of α,β‐Unsaturated Ketones with O‐(2,4‐Dinitrophenyl)‐hydroxylamine.

AbstractTitle aziridination reaction of alkenyl aryl ketones (I) provides trans‐disubstituted aziridines (II), exclusively.

Synthesis of Angularly Fused Aromatic Compounds from Alkenyl Enediynes by a Tandem Radical Cyclization Process

Let's get radical: A general synthetic route toward angularly ortho-fused polyaromatic [4]helicenes starting from aryl alkenyl N-substituted cyclic enediynes is described (see scheme; DMSO=dimethyl sulfoxide, Ns=4-nitrobenzenesulfonyl). The process involved a Bergman cyclization (BC) as the key step of an unprecedented tandem radical reaction. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.