Regioselectivity‐Switchable Intramolecular Hydroarylation of Ynone

Transition metal-catalyzed transformations of 2-formylarylboronic acids

2-Formylarylboronic acids are easily available precursors in organic chemistry. Different types of transition metal catalysts, such as Pd(0), Pd(II), Rh(I), Ir(I), Ni(II), Cu(I), Cu(II), and Co(II), can efficiently catalyze coupling reactions of 2-formylarylboronic acids with other organic reactants. In this review, we describe the synthesis of a diverse range of carbocyclic and heterocyclic compounds, as well as acyclic compounds, via transition metal-catalyzed reactions of 2-formylarylboronic acids over the past two decades.

Asymmetric Gold(I)‐Catalyzed Tandem Hydroarylation–Nazarov Cyclization: Enantioselective Access to Cyclopentenones

The asymmetric synthesis of cyclopentachromenones from gold‐catalyzed reaction of readily available skipped alkenynones is described. This cascade reaction involves an initial anti‐Michael hydroarylation of the ynone moiety to form a gold‐functionalized dialkenylketone intermediate, followed by a Nazarov cyclization that proceeds in an unprecedented enantioselective manner. Excellent enantiomeric ratios and chemical yields are obtained under mild reaction conditions.

Rhodium-catalyzed coupling-cyclization reaction of isocyanides and 2-azidophenyloxyacrylates: synthesis of N-(3-substituted benzo[d]oxazol-2(3H)-ylidene)amines and dihydrobenzo[d]oxazoles

A rhodium-catalyzed coupling cyclization of isocyanides with 2-azidophenyloxyacrylates has been developed. The reaction provides a new method for the synthesis of N-(3-substituted benzo[d]oxazol-2(3H)-ylidene)amines and dihydrobenzo[d]oxazoles.

Electrochemical Selenylative Carbannulation of Biaryl Ynones to Seleno-Dibenzocycloheptenones/Spiro[5.5]Trienones

Electrooxidative-induced synthesis of structurally diverse seleno-dibenzocyclohepten-5-ones and seleno-spiro[5.5]trienones by selenylative carbannulation of biaryl ynones with diaryl diselenide has been developed. The switchable reactivity, intramolecular ortho-annulation or dearomative ipso-annulation, is directed by the substituent present on the ortho-aryl group of aryl-ynone. The prominent features of this method include metal-free, external chemical oxidant-free conditions, and readily accessible substrates.

Electro-Oxidative C-N Bond Formation through Azolation of Indole Derivatives: An Access to 3-Substituent-2-(Azol-1-yl)indoles

A practical protocol to synthesize 3-substituent-2-(azol-1-yl)indole derivatives has been developed via an electrochemical oxidative cross coupling process under mild conditions. This electro-oxidative C-N bond formation strategy tolerates a range of functional groups and is amenable to gram scale synthesis. Moreover, this method was applied to the late-stage functionalization of bioactive molecules.

Metal-Free Intramolecular [3+2] Cycloaddition of γ-Hydroxy Acetylenic Ketones with Alkynes for the Synthesis of Naphtho[1,2-c]furan-5-ones and Its Derivatization via a Selective C(sp2)-H Deuteration Reaction

A metal-free intramolecular [3+2] cycloaddtion has been achieved by treating benzene-linked propynol-ynes with AcOH/H₂O in a one-pot manner. The reaction provides greener, 100% atom-economic, highly regioselective, and more practical access to functionalized naphtho[1,2-c]furan-5-ones with valuable and versatile applications. The regioselective α-deuteration of naphtho[1,2-c]furan-5-ones has been also presented with excellent deuterium incorporation and chemical yields. Moreover, the fluorescent properties of naphtho[1,2-c]furan-5-one products have been investigated in solution.

Gold-Catalyzed Spirocyclization of Furan-ynones and Unexpected Skeleton Rearrangement of the Resulting Spirohydrofurans

A gold-catalyzed cyclization of aniline-tethered furan-ynones has been developed. The reaction proceeds via trapping of the resulting stabilized cationic intermediate with an amide group leading to polycycles featured with a spiro-cyclohexadienone-hydrofuran framework with high efficiency. The resulting N-alkyl products undergo photorearrangements to afford the ring-enlarged benzo[b]azepine derivatives or iron-promoted novel rearrangement to diketone-containing spirocycles involving multiple C-X bond cleavages and formations.

In(ONf)3-catalyzed 7-membered carbon-ring-forming annulation of heteroarylindoles with α,β-unsaturated carbonyl compounds

We developed the two recipes, on the indium-catalyzed reductive and oxidative 7-membered carbon-ring-forming annulations of heteroarylindoles with a,β-unsaturated carbonyl compounds.

Construction of Partially Protected Nonsymmetrical Biaryldiols via Semipinacol Rearrangement of o-NQM Derived from Enynones

The construction of partially protected nonsymmetrical biaryldiols catalyzed by AgBF₄ has been achieved. The approach facilitates the formation of two new aryl rings and the introduction of two hydroxyl groups (one free and one TBS-protected) via the o-NQM generation/semipinacol rearrangement cascade, featuring high atom- and step-economy to afford a diverse array of partially protected nonsymmetrical biaryldiols under mild conditions.