Auf dem Wege zu Tribenzoacepentalen: Tribenzotriquinacen, Dihydrotribenzoacepentalendiid und das Tribenzoacepentalen‐Radikalanion

Abstract

Dreifach benzoanellierte Kohlenwasserstoffe sind die vier Titelverbindungen 1 – 4. Während 1 noch nicht synthetisiert werden konnte, ist 2 auf einem neuen Weg gut zugänglich und läßt sich leicht in 3 und 4 überführen. Beide sind stabiler als die analogen Derivate von Acepentalen.

Three-Dimensional Hydrocarbon Cores Based on Multiply Fused Cyclopentane and Indane Units: Centropolyindanes

“…Besides the discussion on the long-assumed homoconjugative interaction between the π bonds of 18 , − the generation and properties of the triquinacene-10-yl cation was put forward. ,, Many bridgehead-functionalized derivatives of triquinacene, such as 19 , − a few centro -substituted ones, e.g., 20 , , and peripherally functionalized ones, e.g., the interesting all- exo -hexaol 22 , have been described and studied, mainly with respect to their reactivity toward complexation with metal carbonyl fragments, reduction, and elimination. The deprotonation/dehydrogenation pathways of 18 and some derivatives by use of superbases have also been studied in great detail, ,− and the existence of neutral acepentalene ( 23 ), having remained elusive in condensed media, was demonstrated in the gas phase . More recently, the azatriquinacenes, including the parent, convex/concave heterocentropolyquinane 24 , have attracted some attention because of the particularly exposed basic nitrogen center. −

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“…Bridgehead-heterofunctionalized dehydrotribenzotriquinacenes (or dihydrotribenzoacepentalenes), such as compound 136 mentioned above, can also be prepared from 42 and related centro -alkyl-substituted tribenzotriquinacenes (e.g., 43 ) by a completely independent route (Scheme 25), ,,− which has found strikingly close parallels in the chemistry of triquinacene ( 18 ). ,,− Deprotonation of the three bridgehead C−H bonds of 42 and 43 by use of Lochmann−Schlosser bases gives rise to dipotassium dihydroacepentalenediide salt 141 , which can be quenched by a variety of electrophiles, such as alkyl, phenylselenyl, and trialkylsilyl and -stannyl halides. , The corresponding reaction with methyl chloroformate yields the highly strained diester 142 . It is noteworthy that careful hydrolysis of the intermediate dipotassium dihydroacepentalenediide 141 at −78 °C gives rise to the parent dihydroacepentalene 143 , which was found to undergo Diels−Alder addition with anthracene to give 144 as well as with tetracyclone and 1,3-diphenylisobenzofuran.…”

Utility of the Tandem Pauson−Khand Reaction in the Construction of Tetracycles

“…During the last two decades interest in the study of molecules that contain significant amounts of strain energy in their molecular structure has increased. The questions of bonding character, π overlap, and Hückel stabilization are of great importance to computational and organic chemists. − The desire to better understand the bonding character of carbon has prompted the study of the synthesis of a number of strained molecules termed polyquinenes . Dicyclopenta[ a,e ]pentalene ( 1 ) and dicyclopenta[ a,f ]pentalene ( 2 ) (Figure ) have not been synthesized and have been discussed only from a computational point of view.…”

Multiple Vinylation of Tribenzotriquinacenes and Fenestrindanes at Their Aromatic Peripheries by Use of Nájera’s Catalyst

“…[3,9] While the "exhaustive" Sonogashira and Suzuki coupling of tribenzotriquinacenes 3a and 3b, respectively, was found to occur in very good yields, [3] the corresponding reactions of the fenestrindanes 4a and 4b gave only moderate yields (29-35 %), and a marked propensity for partial reduction of the halogene functionalities. [9,14,[25][26][27] In fact, separation of minor amounts of the corresponding sevenfold C-C coupled fenestrindanes formed as a by-produces in both the Sonogashira and Suzuki coupling reactions proved to be difficult with fenestrindanes. Nevertheless, multiple vinylation by Pd 0 -catalyzed C-C coupling at the aromatic peripheries of the bowl-shaped framework of tribenzotriquinac- www.eurjoc.org enes 3 and saddle-like skeleton of fenestrindanes 4 represents a particular challenge since such compounds could prove useful for several further conversions, e.g., to novel cyclophanes consisting of two tribenzotriquinacene units.…”