Gold(I)-Mediated Cyclizations of Triene-Yne Systems: An Easy Access to Cyclopenta-Fused Anthracenes

The direct synthesis of cyclopenta-fused anthracenes (CP-anthracenes) through a gold(I)-catalyzed cyclization reaction of easily available triene-yne systems bearing a benzofulvene substructure, is reported. The targets are of great interest due to the potential use as organic materials and the preparation of these compounds is gaining huge importance. The applied starting materials are readily available through a three-step synthesis, which further contributes to the advantages of this route. In addition, UV-Vis and fluorescent spectra of the obtained CP-anthracenes were recorded.

Recent Developments with Icetexane Natural Products

Icetexane diterpenoids are a diverse family of natural products sourced from several species of terrestrial plants. Icetexanes exhibit a broad array of biological activities and together with their complex 6-7-6 tricyclic scaffolds, they have piqued the interest of synthetic organic chemists, natural products chemists, and biological investigators over the past four decades and were reviewed 13 years ago. This review summarizes icetexane natural products isolated since 2009, provides an overview of new synthetic approaches to the icetexane problem, and proposes an additional classification of icetexanes based on novel structures that are unlike previously isolated materials.

The formation of benzoxacin-3-ones via intramolecular Nicholas reactions and synthesis of 8-membered heliannuols

The γ-carbonyl cations generated from propargyl ether-Co₂(CO)₆ complexes undergo intramolecular Nicholas reactions to give dehydrobenzoxacin-3-one-Co₂(CO)₆ complexes in good yields. Reductive decomplexation and subsequent manipulation allows the synthesis of (±)-heliannuol K methyl ether and the formal syntheses of (±)-heliannuol K, (±)-heliannuol A, and (-)-heliannuol L.

Anionic Diels-Alder Chemistry of Cyclic Sodium Dien-1-olates Delivering Highly Stereoselective and Functionalized Polycyclic Adducts

Anionic Diels–Alder chemistry of electron-deficient cross-conjugated vinylogous alkenones, providing highly stable sodium dienolate ion pairs as electron-rich dienes in the presence of a weak sodium base in THF, has been newly developed, leading to a single Diels–Alder adduct, in racemic form, in moderate to high yields (up to 97%, 37 examples).

Generation and Reactions of a Benzodehydrotropylium Ion-Co2(CO)6 Complex

A series of 7-methylenedehydrobenzo[7]annulen-5-ol hexacarbonyldicobalt complexes were generated by Hosomi-Sakurai reactions of allylsilanes containing o-alkynylarylaldehyde-Co₂(CO)₆ complexes. One of the cyclization products was converted into its corresponding dihydrobenzo[7]annulen-7-ol hexacarbonyldicobalt complex, an immediate precursor to a benzodehydrotropylium-Co₂(CO)₆. The cation was generated in situ and reacted with four nucleophiles, and its aromatic stabilization was determined by computational methods.

Expedient synthesis of a symmetric cycloheptyne-Co2(CO)6 complex for orthogonal Huisgen cycloadditions

A cycloheptyne dicobalt-carbonyl complex with a terminal alkyne was synthesized by a short procedure, and was able to react selectively in Strain Promoted Alkyne Azide Cycloaddition (SPAAC) or Copper Catalysed Alkyne Azide Cycloaddition (CuAAC) depending on the conditions.

A Strategy toward Icetexane Natural Products

Icetexane diterpenoids are richly complex polycyclic natural products that have been described with a variety of biological activities. We report here a general synthetic approach toward the 6-7-6 tricyclic core structure of these interesting synthetic targets based on a two-step enolate alkylation and ring-closing metathesis reaction sequence.

Cobalt(II)-Catalyzed Aerobic Oxidation of Terminal-Capped Alkynyl α-Cyano Alkanone Systems. An Oxygen-Mediated Radical Chain Reaction

A new N-hydroxyphthalimide (NHPI)/Co(II)-catalyzed protocol, mechanistically involving a sequence of α-hydrogen abstraction, 5-exo-dig cyclization, oxygen capture, hydrogen transfer, and 1,4-dehydration, has been developed to facilitate aerobic oxidation of aryl-, silyl-, and alkyl-capped alkynyl α-cyano alkanone systems to the corresponding highly functionalized products in an effective manner, thus turning this novel chain reaction, originally occurring spontaneously in low yields, into a practical methodology.