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ConspectusOrganic synthesis based on straightforward transformations is essential for environmentally benign manufacturing for the invention of novel pharmaceuticals, agrochemicals, and organoelectronic materials in order to ultimately realize a sustainable society. Metal-catalyzed C–H bond-cleaving functionalization has become a promising method for achieving the above goal. For site-selective C–H bond cleavage, so-called directing groups, i.e., ligands attached to substrates, are employed. Commonly utilized directing groups are carbonyls, imines, carboxyls, amides, and pyridyls, which σ-donate electron pairs to metals. On the other hand, unsaturated substrates such as alkenes and alkynes, which participate largely as reactants in organic synthesis, are prepared readily by a wide variety of synthetic transformations and are also employed as reactants in organometallic chemistry. Moreover, such unsaturated groups form complexes with some metals by ligation of their p orbitals via donation and back-donatio...

Palladium(0)-catalyzed insertion/annulation sequence between aryl silylethynyl ethers and internal alkynes was found to proceed through activation of ortho-C–H bonds assisted by alkynoxy groups and...

o-Alkynylphenols are found to undergo a Pd/Zn-catalyzed dehydrogenative formation of benzocyclobutene derivatives involving the o-alkynyl substituent as internal hydrogen acceptor.

The title transformation can be achieved by the o-C–H cleavage of alkynyl aryl ethers, which is easily derived from phenols, followed by the insertion/annulation with isocyanates in the presence of a palladium catalyst. Various alkynyl aryl ethers and arylisocyanates are applied to this transformation to give the corresponding cyclic products. Mechanistic study indicates that the C–H cleavage is effected reversibly by the concerted metalation-deprotonation pathway. The products exhibit solid-state luminescence upon irradiation of UV light. Fluorescent maxima and quantum yields can be controlled by the substituents at appropriate sites in the products.

The intramolecular hydroarylation of 2-(silylethynyloxy)-biaryls affords the corresponding cyclized products with a Z-configurated silylethynyl group.

The reaction can also be applied to the cross-coupling polymerization for the synthesis of triarylamine copolymers by reacting (XII) with (XIV) or (XVI), respectively.

The palladium-catalyzed cycloaddition of alkynyl aryl ethers (I) to various allenes gives benzopyran derivatives.

The present reaction proceeds not only for silylated alkynes but also for substrates bearing a carbonaceous substituent.

Cross-coupling reactions of dibromoarenes (I), (IV), and (VI) with HOMSi reagents (organo[2-hydroxymethylphenyl]dimethylsilanes) (II) or alternatively bromoarenes (IX) and arylene-bisHOMSi reagents, e.g. (VIII), afford ter- or quaterarenes (III), (V), (VII), and (X), resp., in high yields.

Silylalkynyl aryl ethers and internal alkynes give under optimized conditions silylmethylidene-substituted chromenes.

The process affords functionalized 1-azadienes, generally with excellent (E) or (Z) selectivity.

Intermolecular CO-retained carbothiolation of alkynes using thioesters took place to afford β-SR substituted enone derivatives; the choice of catalyst (Pd(dba)2–dppe) and the introduction of a CF3 group into the thioesters are the key to achieving the transformation.