Synthesis of the tetracyclic core of anthracycline antibiotics by an intramolecular dehydro Diels-Alder approach

A mild tetradehydro-Diels-Alder reaction of aryldiyne compounds affords exclusively linear products

The thermal tetradehydro-Diels-Alder (TDDA) reaction for the synthesis of polysubstituted aromatic compounds remains underestimated probably due to the harsh conditions and multiproduct results. Herein, a mild intramolecular TDDA reaction of aryldiyne compounds is presented with linear naphthalenes only, exhibiting good functional group tolerance. The reaction is easy to operate and amenable to multigram-scale synthesis. From the preliminary work, it was found that the mild conditions may be the key to the completely linear product in the reactions.

Recent advances in the syntheses of anthracene derivatives

Anthracene and anthracene derivatives have been extensively studied over the years because of their interesting photophysical, photochemical, and biological properties. They are currently the subject of research in several areas, which investigate their use in the biological field and their application in OLEDs, OFETs, polymeric materials, solar cells, and many other organic materials. Their synthesis remains challenging, but some important preparative methods have been reported, especially in the last decade. This review presents an update of the recent strategies that have been employed to prepare anthracene derivatives. It encompasses papers published over the last twelve years (2008–2020) and focuses on direct and indirect methods to construct anthracene and anthraquinone frameworks.

Organocatalyzed benzannulation for the construction of diverse anthraquinones and tetracenediones

An efficient one-pot synthesis of anthraquinones and tetracenediones was achieved via L-proline catalyzed [4+2] cycloaddition of in situ generated azadiene from α,β-unsaturated aldehydes and 1,4-naphthoquinones or 1,4-anthracenedione in good to excellent yield. This protocol constitutes an unprecedented tandem benzannulation that allows one-pot construction of diverse anthraquinones and tetracenediones in the presence of organocatalysts. This methodology was applied successfully to the synthesis of naturally occurring molecules and photochemically interesting phenanthrenequinone derivatives.

Anionic sigmatropic-electrocyclic-Chugaev cascades: accessing 12-aryl-5-(methylthiocarbonylthio)tetracenes and a related anthra[2,3-b]thiophene

1,4-Diols resulting from the double addition of ArCCLi (Ar = Ph, substituted phenyl, 2-thienyl) to ortho-C6H4(CHO)2 undergo cascades to tetracenes on simple admixture of LiHDMS, CS2 and MeI. Acene formation proceeds by [3,3]-sigmatropic rearrangement of xanthate anions followed by 6π electrocyclisations. The reactions are terminated by E2 or anionic Chugaev-type eliminations. Structural packing motifs and electronic properties are reported for the tetracenes.

Nonstatistical dynamics in the thermal Garratt-Braverman/[1,5]-H shift of one ene-diallene: an experimental and computational study

A mechanistic study of the thermal Garratt-Braverman/[1,5]-H shift of ene-diallene 6 leading to alkenes (E)-8 and (Z)-8 is reported. The product ratio was found to be temperature-independent and does not agree with the computed energy barriers (i.e., TS2E(⧧) and TS2Z(⧧)). On the basis of experimental and DFT computational results, we propose a mechanism that is strongly controlled by nonstatistical dynamic effects.

Flexible synthesis of anthracycline aglycone mimics via domino carbopalladation reactions

A synthesis of anthracycline aglycone derivatives is described. The key step utilizes a powerful domino carbopalladation approach and subsequent ring closure. During this process two of the four rings of the anthracycline scaffold are formed. Differently substituted carbohydrates and dialkyne chains serve as versatile and simple starting materials for the reaction sequence. Diverse building blocks lead to a variety of different products and a broad range of structural diversity.

Synthesis of Tetracene Sulfoxide and Tetracene Sulfone via a Cascade Cyclization Reaction

A facile synthesis of tetracene sulfoxides and sulfones based on o-diallene annulation initiated cascade cyclization was developed. The photophysical behavior of these tetracene derivatives can be generally rationalized by the presence of electron-withdrawing sulfoxides and sulfones at the 5-position.