Cobalt-Catalyzed Formal [4+2] Cycloaddition of α,α′-Dichloro-ortho-Xylenes with Alkynes

Palladium-Catalyzed Dearomatization of Indoles with Alkynes: Construction of Spirocyclohexaneindolenines

A palladium-catalyzed dearomatization of indoles with alkynes has been developed, providing an efficient route to access a variety of synthetically useful spirocyclohexaneindolenines in moderate to good yields. The current method features a simple catalytic system, operational simplicity, and good functional group compatibility, which will contribute substantially to the development of dearomatization to access spiro compounds. Besides, the ubiquitous existence of spiro molecules, including spirocyclohexaneindolenines, in drugs and biological active molecules suggests the potential application of this methodology in medicinal chemistry.

Cobalt-Catalyzed Enantiospecific Dynamic Kinetic Cross-Electrophile Vinylation of Allylic Alcohols with Vinyl Triflates

Asymmetric cross-electrophile coupling has emerged as a promising tool for producing chiral molecules; however, the potential of this chemistry with metals other than nickel remains unknown. Herein, we report a cobalt-catalyzed enantiospecific vinylation reaction of allylic alcohol with vinyl triflates. This work establishes a new method for the synthesis of enantioenriched 1,4-dienes. The reaction proceeds through a dynamic kinetic coupling approach, which not only allows for direct functionalization of allylic alcohols but also is essential to achieve high chemoselectivity. The use of cobalt enables the reactions to proceed with high enantiospecificity, which have failed to be realized by nickel catalysts.

Helicene synthesis by Brønsted acid-catalyzed cycloaromatization in HFIP [(CF3)2CHOH]

A facile synthesis of carbo- and heterohelicenes was achieved via tandem cycloaromatization of bisacetal precursors, which were readily prepared through C–C bond formation by Suzuki–Miyaura coupling. This cyclization was efficiently realized by a catalytic amount of trifluoromethanesulfonic acid (TfOH) in a cation-stabilizing solvent, 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP), which readily allowed gram-scale syntheses of higher-order helicenes, double helical helicenes, and heterohelicenes.

Synthesis of polycyclic naphthols and naphthalenes via tandem Ti(Oi-Pr)4-promoted photoenolization Diels–Alder reaction and aromatization

An efficient approach to naphthol and naphthalene scaffolds has been developed using a sequence involving tandem Ti(Oi-Pr)₄-promoted photoenolization Diels–Alder (PEDA) and aromatization reactions.

Regioselective arene homologation through rhenium-catalyzed deoxygenative aromatization of 7-oxabicyclo[2.2.1]hepta-2,5-dienes

A facile approach to PAHs with an arm-chair edge via regioselective bromination, Diels–Alder reaction, and rhenium-catalyzed deoxygenative aromatization is described.

Three-component coupling of aryl iodides, allenes, and aldehydes catalyzed by a Co/Cr-hybrid catalyst

The cobalt/chromium-catalyzed three-component coupling of aryl iodides, allenes, and aldehydes has been developed to afford multi-substituted homoallylic alcohols in a diastereoselective manner. Control experiments for understanding the reaction mechanism reveal that the cobalt catalyst is involved in the oxidative addition and carbometalation steps in the reaction, whereas the chromium salt generates highly nucleophilic allylchromium intermediates from allylcobalt species, without the loss of stereochemical information, to allow the addition to aldehydes.

Sequential σ-Bond Insertion/Benzannulation Involving Arynes: Selective Synthesis of Polysubstituted Naphthalenes

An interesting σ-bond insertion/benzannulation reaction for the synthesis of polysubstituted naphthalene derivatives has been developed from readily accessible ketones, arynes, and alkynoates. This practical and transition-metal-free method provides a novel route to diverse naphthalenes through a substrate-controlled rearrangement reaction with the cleavage of C-C bonds.

Highly nucleophilic vitamin B12-assisted nickel-catalysed reductive coupling of aryl halides and non-activated alkyl tosylates

Reductive cross-coupling of aryl halides with ubiquitous alkyl tosylates was developed using a combination of nickel and vitamin B₁₂ (VB₁₂: cyanocobalamin) catalysts. The tosylate was activated by reduced VB₁₂ to form alkyl cobalt(iii), which served as a good alkylating agent for aryl-nickel species, leading to C(sp³)-C(sp²) bond formation.

Trisubstituted olefin synthesis via Ni-catalyzed hydroalkylation of internal alkynes with non-activated alkyl halides

The stereoselective synthesis of tri-substituted alkenes is challenging.

Azaacenes as active elements for sensing and bio applications

Recent progress in the application of azaacenes in sensing and bio-fields has been summarized.

The drastic effect of cobalt and chromium catalysts in the borylation of arylzinc reagents

A new synthetic approach to arylboronic esters from arylzinc reagents with boryl electrophiles MeOB(OR)₂ has been developed. Furthermore, this protocol could be applied to the cyclization/borylation of alkynylaryl iodides to afford cyclized vinylboronic esters.