Alkyne-alkyne Coupling Research Articles

Convenient syntheses of phthalocyanine and tetrabenzotriazaporphyrin (TBTAP) mono-alkynes; unhindered building blocks for click chemistry and beyond

Unsymmetrical phthalocyanines and related macrocycles are often desirable for covalent construction or the self-assembly of more complex architectures. Terminal alkynes are versatile in this regard because they are amenable to cross-coupling via Sonogashira-type reactions, alkyne-alkyne coupling via Glaser-type couplings, and triazole formation via Click reaction with azides. Here we describe two complementary syntheses to conveniently add a single alkyne onto the phthalocyanine peripheral position and onto the meso-phenyl group of an (aryl)tetrabenzotriazaporphyrin, here providing a remote link point that is insulated from the macrocycle.

Interfacial synthesis of crystalline two-dimensional cyano-graphdiyne.

A well-defined crystalline cyano-functionalized graphdiyne (CN-GDY) is synthesized at a liquid/liquid interface through alkyne-alkyne coupling reactions. The configurations and nanostructures of CN-GDY were well characterized by TEM, SEM, AFM, XPS, and Raman spectroscopy. HR-TEM and selected area electron diffraction (SAED) in combination with structure simulation firmly revealed a 9-fold stacking mode for CN-GDY.

Synthesis of a 1,3-Bridged Macrobicyclic Enyne via Chemoselective Cycloisomerization Using Palladium-Catalyzed Alkyne-Alkyne Coupling.

A unique intramolecular Pd-catalyzed alkyne-alkyne coupling is presented. This transformation generates a strained, 1,3-bridged, macrocyclic enyne. The process was readily executed on gram scale, and the structure of the product was elucidated via X-ray crystallographic analysis. A mechanistic rationale for the observed chemoselectivity is provided.

Synthesis of Angularly Substituted trans-Fused Decalins through a Metallacycle-Mediated Annulative Cross-Coupling Cascade.

A convergent coupling reaction is described that enables the stereoselective construction of angularly substituted trans-fused decalins from acyclic precursors. The process builds on our alkoxide-directed titanium-mediated alkyne-alkyne coupling and employs a 1,7-enyne coupling partner. Overall, the reaction is thought to proceed through initial formation of a tetrasusbstituted metallacyclopentadiene, stereoselective intramolecular [4+2] cycloaddition, elimination, isomerization, and regio- and stereoselective protonation. Distinct from our early studies directed at the synthesis of trans-fused hydrindanes, the current annulative coupling reveals an important effect of TMSCl in controlling the final protonation-the event that establishes the stereochemistry of the ring fusion.

Asymmetric Synthesis of Dihydroindanes by Convergent Alkoxide-Directed Metallacycle-Mediated Bond Formation

A convergent synthesis of highly substituted and stereodefined dihydroindanes is described from alkoxide-directed Ti-mediated cross-coupling of internal alkynes with substituted 4-hydroxy-1,6-enynes (substrates that derive from 2-directional functionalization of readily available epoxy alcohol derivatives). In addition to describing a new and highly stereoselective approach to bimolecular [2 + 2 + 2] annulation that delivers products not available with other methods in this area of chemical reactivity, evidence is provided to support annulation by way of regioselective alkyne-alkyne coupling, followed by metal-centered [4 + 2] rather than stepwise alkene insertion and reductive elimination. Overall, the reaction proceeds with exquisite stereochemical control and defines a convenient, convergent, and enantiospecific entry to fused carbocycles of great potential value in target-oriented synthesis and medicinal chemistry.

Convergent Synthesis and Discovery of a Natural Product-Inspired Paralog-Selective Hsp90 Inhibitor

A convergent synthesis of benzoquinone ansamycin analogs is described that proceeds by a sequence of metallacycle-mediated alkyne-alkyne coupling, followed by site- and stereoselective dihydroxylation and global carbamate formation. These studies have led to (1) validation of alkyne-alkyne coupling to produce geldanamycin analogs that lack the problematic quinone, (2) the discovery that C6-C7 bis-carbamate functionality is compatible with Hsp90 inhibition, and (3) the identification of 1 as a nonquinone geldanamycin-inspired paralog-selective Hsp90 inhibitor.

Total synthesis of bryostatin 16 using a Pd-catalyzed diyne coupling as macrocyclization method and synthesis of C20-epi-bryostatin 7 as a potent anticancer agent.

Asymmetric total synthesis of bryostatin 16 was achieved in 26 steps in the longest linear sequence and in 39 total steps from aldehyde 10. A Pd-catalyzed alkyne-alkyne coupling was employed for the first time as a macrocyclization method in a natural product synthesis. A route to convert bryostatin 16 to a new family of bryostatin analogues was developed. Toward this end, 20-epi-bryostatin 7 was synthesized from a bryostatin 16-like intermediate; the key step involves a Re-catalyzed epoxidation/ring-opening reaction. Preliminary biological studies indicated that this new analogue exhibits nanomolar anti-cancer activity against several cancer cell lines.

Synthesis and Characterization of Acetylenic Scaffolds Containing Dithiafulvenes About a Central Anthraquinodimethane Core

A large conjugated chromophore containing four redox-active dithiafulvenes about a central anthraquinodimethane core and a new alkyne-extended tetrathiafulvalene has been synthesized by alkyne-alkyne coupling reactions. Studies of the optical and redox properties of these acetylenic scaffolds have been performed.

Iridium complex catalyzed carbonylative alkyne-alkyne coupling for the synthesis of cyclopentadienones.

[reaction: see text]. Catalytic carbonylative alkyne-alkyne coupling proceeds using iridium-phosphine complexes under carbon monoxide at atmospheric pressure or a partial pressure of 0.2 atm. This reaction provides various cyclopentadienones in high isolated yields.

Direct synthesis of cyclopentadienones by cobalt carbonyl-mediated carbonylative alkyne-alkyne coupling reaction

Dicobalt carbonyl complex mediates an intermolecular carbonylative coupling reaction between alkynylsilanes. The reaction proceeds under atmospheric pressure of argon and directly provides free cyclopentadienones in high yields (up to 99%).