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

Abstract

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

Dibenzo[a,o]phenanthro[3,4-s]pycene, a Configurationally Stable Double Helicene: Synthesis and Determination of Its Conformation by NMR and GIAO Calculations

“…The mixed-sense conformer 5 - PM was the more stable by 3.1 kcal/mol. Although AM1 is known to be reliable for conformational analysis of helicenes and other helically twisted polyarenes,10c we further optimized the obtained geometries of 5 using ab initio HF/6-31G(d) calculations and the hybrid DFT method B3LYP/6-31G(d), , which confirmed 5 - PM as the more stable conformer by 5.0 or 4.6 kcal/mol, respectively. The barrier to interconversion of 5 - PP into 5 - PM via the transition state 5 -TS (Figure ) was calculated at the AM1 level to be 21.8 kcal/mol.…”

“…In recent years, we have applied a new, palladium-catalyzed cyclotrimerization of arynes to the synthesis of a number of strained polycyclic aromatic hydrocarbons, some of which contain helical fragments. In particular, compound 2 is the major product of the trimerization of the two-ring aryne 1,2-didehydronaphthalene ( 1 ) 10b.…”

“…In recent years, we have applied a new, palladium-catalyzed cyclotrimerization of arynes to the synthesis of a number of strained polycyclic aromatic hydrocarbons, some of which contain helical fragments. In particular, compound 2 is the major product of the trimerization of the two-ring aryne 1,2-didehydronaphthalene ( 1 ) 10b. In this paper, we describe the cyclotrimerization of the three-ring aryne 3,4-didehydrophenanthrene ( 4 ) to form compound 5 (as far as we know, the first double helicene formed by a pentahelicene and a heptahelicene with two rings in common), and we sketch the elucidation of the relative stereochemistry of the two helicenes constrained in this product.…”

Aryne Cycloaddition Reactions in the Synthesis of Large Polycyclic Aromatic Compounds

“…Picene derivative 17 was isolated as a minor product of the palladium‐catalysed [2+2+2] co‐cycloaddition involving 1,2‐naphthyne ( 13 ) and dimethyl acetylenedicarboxylate (DMAD) (Scheme ) 34. The palladium‐catalysed cyclotrimerization of benzyne20 and the chemoselective co‐trimerization with electron‐deficient alkynes21a had been previously developed by our group as the first metal‐catalysed transformations involving arynes. This approach represented a breakthrough in the field of aryne chemistry.…”

“…Thus, although the [2+2]18 or [4+2] (Diels–Alder)19 cycloaddition reactions of arynes have been known for a long time, the first metal‐catalysed reactions were described by our group in the late 90s with the palladium(0)‐catalysed cyclotrimerization of benzyne to yield triphenylene 20. Shortly after, the [2+2+2] co‐cycloaddition of benzynes with electron‐deficient alkynes was reported, and this proved to be chemoselective in allowing the preferential formation of either phenanthrenes or naphthalenes depending on the palladium catalyst employed 21.…”