Dolores Pérez

EFFICIENT PALLADIUM-CATALYZED CYCLOTRIMERIZATION OF ARYNES : SYNTHESIS OF TRIPHENYLENES

Found at the core of many discotic liquid crystals, triphenylenes can now be synthesized efficiently by the palladium-catalyzed trimerization of arynes, including those containing donor and acceptor substituents [Eq. (a); R=OMe, F].

On-surface generation and imaging of arynes by atomic force microscopy

Reactive intermediates are involved in many chemical transformations. However, their characterization is a great challenge because of their short lifetimes and high reactivities. Arynes, formally derived from arenes by the removal of two hydrogen atoms from adjacent carbon atoms, are prominent reactive intermediates that have been hypothesized for more than a century. Their rich chemistry enables a widespread use in synthetic chemistry, as they are advantageous building blocks for the construction of polycyclic compounds that contain aromatic rings. Here, we demonstrate the generation and characterization of individual polycyclic aryne molecules on an ultrathin insulating film by means of low-temperature scanning tunnelling microscopy and atomic force microscopy. Bond-order analysis suggests that a cumulene resonance structure is the dominant one, and the aryne reactivity is preserved at cryogenic temperatures. Our results provide important insights into the chemistry of these elusive intermediates and their potential application in the field of on-surface synthesis.

From Perylene to a 22‐Ring Aromatic Hydrocarbon in One‐Pot

The successful synthesis of a threefold symmetric C78H36 molecule with 22 fused benzene rings is reported. This clover-shaped nanographene was characterized on an ultrathin insulating film with atomic resolution by scanning probe microscopy.

[16]Cloverphene: a Clover-Shaped cata-Condensed Nanographene with Sixteen Fused Benzene Rings.

Abstract Cloverphenes are graphene-type polyarenes, the structures of which resemble the threefold symmetry of clover leafs. In their Communication (10.1002/anie.201104935), D. Pena and co-workers present the synthesis and properties of a nanosized [16]cloverphene derivative, which consists of 16 fused benzene rings (22 benzene rings in total) and 102 sp(2) -hybridized atoms. The synthesis involves sequential [4+2] and [2+2+2] aryne cycloadditions.

Die erste effiziente Palladium‐katalysierte Cyclotrimerisierung von Arinen: Synthese von Triphenylenen

Von reaktiven Zwischenstufen zu nutzlichen Produkten gelangt man durch die Palladium-katalysierte Trimerisierung intermediar gebildeter 1,2-Didehydrobenzole, die auch Donor- oder Acceptor-substituiert sein konnen [Gl. (a); R=OMe bzw. F]. Die dabei unter milden Bedingungen erhaltenen Triphenylene sind die zentrale Struktureinheit vieler Verbindungen, die discotische Flussigkristalle bilden.

Highly Selective Insertion of Arynes into a C(sp)−O(sp3) σ Bond

Arynes react with ethoxyacetylene to afford 2-ethoxyethynylaryl derivatives through a highly chemo- and regioselective formal insertion of the aryne into the C(sp)-O(sp(3)) bond of the alkyne. Computational studies suggest that the reaction does not proceed through a mechanism initiated by the nucleophilic addition of the oxygen atom to the aryne as previously proposed but by the addition of the triple bond of the alkyne to the aryne.

Aryne Insertion into I–I σ-Bonds

A new protocol for the efficient synthesis of o-diiodoarenes has been developed. This method allows the synthesis of substituted and polycyclic o-diiodoarenes, which are difficult to obtain by classical methods. This diiodination process involves the formal insertion of arynes into the I-I σ-bond.

Palladium-catalyzed [2 + 2 + 2] cycloadditions of 3,4-didehydrophenanthrene and 1,2-didehydrotriphenylene.

Palladium-catalyzed [2 + 2 + 2] cycloaddition reactions of 3,4-didehydrophenanthrene (3,4-phenanthryne) and 1,2-didehydrotriphenylene (1,2-triphenylyne) afford sterically congested polycyclic aromatic hydrocarbons with novel structures.

ARYNE-MEDIATED SYNTHESIS OF HETEROCYCLES

Arynes have been used as intermediates in the synthesis of heterocycles with a variety of heteroatoms (O, N, S, Ni, Pd) and rings sizes (from 5 to 8-membered).

Tetracene Formation by On-Surface Reduction

We present the on-surface reduction of diepoxytetracenes to form genuine tetracene on Cu(111). The conversion is achieved by scanning tunneling microscopy (STM) tip-induced manipulation as well as thermal activation and is conclusively demonstrated by means of atomic force microscopy (AFM) with atomic resolution. We observe that the metallic surface plays an important role in the deoxygenation and for the planarization after bond cleavage.