Highly efficient route to fused polycyclic aromatics via palladium-catalyzed aryne annulation by aryl halides
Polycyclic aromatic and heteroaromatic hydrocarbons have been synthesized in high yield by two different processes involving the Pd-catalyzed annulation of arynes. The first process involves a Pd-catalyzed annulation of arynes by 2-halobiaryls and related vinylic halides. The second process utilizes a Pd-catalyzed double annulation of arynes by simple aryl halides. Both processes appear to involve the catalytic, stepwise coupling of two very reactive substrates, an aryne and an organopalladium species, to generate excellent yields of cross-coupled products.
Annulative π-Extension of Unactivated Benzene Derivatives through Nondirected C-H Arylation
Annulative π-extension chemistry provides a concise synthetic route to polycyclic arenes. Herein, we disclose a nondirected annulation approach of unactivated simple arenes. The palladium-catalyzed 2-fold C-H arylation event facilitates tandem C-C linkage relays to furnish fully benzenoid triphenylene frameworks using cyclic diaryliodonium salts. The inseparable regioisomeric mixture of 1- and 2-methyltriphenylenes is identified by the combined analysis of ion mobility-mass spectrometry, gas-phase infrared spectroscopy, and molecular simulation studies.
Lee, Jae Bin,Jeon, Min Ho,Seo, Jeong Kon,Von Helden, Gert,Rohde, Jan-Uwe,Zhao, Bum Suk,Seo, Jongcheol,Hong, Sung You
Proton-catalyzed, silane-fueled friedel-crafts coupling of fluoroarenes
The venerable Friedel-Crafts reaction appends alkyl or acyl groups to aromatic rings through alkyl or acyl cation equivalents typically generated by Lewis acids. We show that phenyl cation. Friedel-Crafts reaction to intramolecular aryl couplings. The enabling feature of this reaction is the exchange of carbon-fluorine for silicon-fluorine bond enthalpies; the reaction is activated by an intermediate silyl cation. Catalytic quantities of protons or silyl cations paired with weakly coordinating carborane counterions initiate the reactions, after which proton transfer in the final aromatization step regenerates the active silyl cation species by protodesilylation of a quaternary silane. The methodology allows the high-yield formation of a range of tailored polycyclic aromatic hydrocarbons and graphene fragments.
Allemann, Oliver,Duttwyler, Simon,Romanato, Paola,Baldridge, Kim K.,Siegel, Jay S.
Palladium-catalyzed annulation of o-iodobiphenyls with o-bromobenzyl alcohols: Synthesis of functionalized triphenylenes via C-C and C-H bond cleavages
Treatment of o-iodobiphenyls with o-bromobenzyl alcohols in the presence of cesium carbonate under palladium catalysis affords a series of highly substituted triphenylenes. The reaction involves two C-C bond formations and C-C and C-H bond cleavages. A combination of palladium and an electron-deficient phosphine ligand proves to be effective for both decarbonylative cross-coupling and intramolecular cyclization.
Synthesis of triphenylene derivatives by Pd-catalyzed Suzuki coupling/intramolecular C–H activation between arylboronic acids and dibromobiphenyls
An efficient and regioselective synthesis of functionalized triphenylenes via palladium-catalyzed Suzuki-Miyaura coupling and subsequent intramolecular C–H activation between arylboronic acids and dibromobiphenyls was developed. This methodology showed excellent atomic economy and regiospecificity as well as synthetic feasibility of unsymmetrical triphenylenes.
Tu, Jingxuan,Li, Gaoqiang,Zhao, Xiaoqian,Xu, Feng
supporting information
p. 44 - 47
(2018/11/30)
Desulfurization of dibenzothiophene and dibenzothiophene sulfone via Suzuki–Miyaura type reaction: Direct access to o-terphenyls and polyphenyl derivatives
The reactivity of dibenzothiophene (DBT) or dibenzothiophene sulfone (DBTO2) with a variety of phenylboronic acids was mediated by the nickel precursor [Ni(dippe)Cl2] in the presence of a base. The reaction was performed under relatively mild conditions (70–100 °C), in aqueous media. The study of the reactivity revealed the role of water as a hydrogen source and showed a competition between the desulfurization of the corresponding substrates via a hydrodesulfurization (HDS) or by a hydrodesulfurative cross-coupling (HDSCC) reaction. Furthermore, in the absence of water sulfur-free poly-phenylic compounds were obtained in good yields as a result of a Suzuki–Miyaura type reaction, being the main product in most of the cases the corresponding o-terphenyl derivative, these products are valuable building blocks in the synthesis of more complex materials.
Gutiérrez-Ordaz, Rubén,García, Juventino J.
p. 373 - 381
(2018/08/31)
Palladium-Assisted "Aromatic Metamorphosis" of Dibenzothiophenes into Triphenylenes
Abstract Two new palladium-catalyzed reactions of aromatic sulfur compounds enabled the conversion of dibenzothiophenes into triphenylenes in four steps. This transformation of one aromatic framework into another consists of 1) 4-chlorobutylation of the dibenzothiophene to form the corresponding sulfonium salt, 2) palladium-catalyzed arylative ring opening of the sulfonium salt with a sodium tetraarylborate, 3) an intramolecular SN2 reaction to form a teraryl sulfonium salt, and 4) palladium-catalyzed intramolecular C-S/C-H coupling through electrophilic palladation. Symmetrical as well as unsymmetrical triphenylenes of interest were synthesized in a tailor-made fashion in satisfactory overall yields. A change of heart: The invention of two palladium-catalyzed arylation reactions of organosulfur compounds enabled the transformation of dibenzothiophenes into triphenylenes and thus a fundamental change in the core aromatic structure (see scheme). Both symmetrical and unsymmetrical triphenylenes were synthesized in a tailor-made fashion in satisfactory overall yield.
Synthesis of Multisubstituted Triphenylenes and Phenanthrenes by Cascade Reaction of o-Iodobiphenyls or (Z)-β-Halostyrenes with o-Bromobenzyl Alcohols through Two Sequential C-C Bond Formations Catalyzed by a Palladium Complex
o-Bromobenzyl alcohol has been developed as a novel annulating reagent, bearing both nucleophilic and electrophilic substituents, for the facile synthesis of polycyclic aromatic hydrocarbons. A palladium/electron-deficient phosphine catalyst efficiently coupled o-iodobiphenyls or (Z)-β-halostyrenes with o-bromobenzyl alcohols to afford triphenylenes and phenanthrenes, respectively. The present cascade reaction proceeded through deacetonative cross-coupling and sequential intramolecular cyclization. An array of experimental data suggest that the reaction mechanism involves the equilibrium of 1,4-palladium migration.