Stereocontrolled Access to Benzo‐Annelated all‐cis‐ and cis,cis,cis,trans‐[5.5.5.6]Fenestranones and all‐cis‐[5.5.5.5]Fenestranes

Abstract

The synthesis of three multiply substituted fenestrindanes (all‐cis‐tetrabenzo[5.5.5.5]fenestranes) is described in detail. Depending on the stereochemical course of the twofold Michael addition of a 1,3‐indanedione to a dibenzylideneacetone in the very first step, the corresponding all‐cis‐tribenzo[5.5.5.6]fenestranones or the strained cis,cis,cis,trans isomers are obtained. In the latter case, stereochemical adjustment to the all‐cis configuration can be achieved by base‐induced epimerization. Conversion of the all‐cis‐[5.5.5.6]fenestranones in five subsequent steps affords the target fenestrindanes bearing either methyl groups at four of the inner (bay) positions or methoxy groups at four or six of the outer (peripheral) positions of the molecular framework.

Enantiopure Aromatic Saddles Bearing the Fenestrindane Core

“…We have been interested in the synthesis of nonplanar π-conjugated derivatives bearing skeletal sp 3 carbons placed outside of the conjugated framework. − In particular, the tetrabenzo[5.5.5.5]­fenestrane (fenestrindane) motif has been utilized to construct polyaromatic saddles. Recently, we reported that 1,4,9,12-tetraarylfenestrindanes ( 5 and 6 ) can undergo 4-fold Scholl-type heptagonal ring closure to furnish the 4-fold cove-bridged derivatives 7 and 8 , respectively (Scheme ).…”

A Perspective on Centrohexaindane Chemistry and a Deep‐Sleeping “Cartesian” Seed

“…Further increase of the degree of substitution at the twelve peripheral positions of centrohexaindane appears challenging but should be possible pursuing the three established routes to the parent hydrocarbon 5. [10,28] On the one hand, it has been shown that, starting with suitably methoxy-functionalized aromatics, the construction of multiply oxy-functionalized triptindanes [32,[51][52][53] and fenestrindanes [54,55] is straightforward. Subsequent incorporation of three or, respectively, two additional anisole-or veratrole-type synthones along the propellane and fenestrane routes with multiple cyclization in the last step of the synthesis offers a number of yet unexplored pathways to, e. g., octafunctionalized derivatives of 5.…”

“…Apart from purely peripheral multiple functionalization of the centrohexaindane skeleton, there are obvious possibilities to construct congeners that bear electron-rich substitutents, such as methoxy groups, in particular, at both selected outer and inner positions of the six indane wings of 5. Based on the known tetramethoxyfenestrindanes 45 [54] and 48, [55b] the fenestrane route offers a straightforward access to the hypothetical octamethoxy derivative 49, even in two complementary ways (Scheme 7). Bridgehead functionalization of 45 and 48 by established methods yielding the corresponding benzhydrylic tetra-alcohols should enable facile condension with dimethoxybenzenes and related building blocks, in analogy to the synthesis shown in Scheme 3.…”

“…The third and fourth variants (47(45 and 47(46) have never been exploited either but would start from the corresponding known tetra-and hexamethoxyfenestrindanes 45 and 46. [54] Functionalization of the four benzhydrylic bridgeheads by bromination and subsequent hydrolysis would afford the corresponding fenestrindanetetrols and allow completion of the fenestrane route by condensation with two electron-rich aromatics in analogy to Scheme 3. Use of veratrole, as depicted in Scheme 6, would furnish the corresponding, yet unknown octa-and decamethoxy-substituted centrohexaindanes.…”

Auf dem Weg vom Fenestrindan zu sattelförmigen Nanographenen mit einem tetrakoordinierten Kohlenstoff‐Atom

“…Ausgehend von zwei Fenestrindan-Vorstufen, 7a bzw. [19,24] Der Te traether 10 wurde dann mittels eines Überschusses an BBr 3 (8 ¾quiv.) Die Verbindungen 8 kçnnen einerseits als versteifte Derivate des o,p,o,p,o,p,o,p-Cyclooctaphenylens (9) [23] aufgefasst werden;a ndererseits stellen sie aufgrund ihrer einzigartigen Molekülgeometrie auch Zwischenstufen auf dem Wegz us attelfçrmigen Fenestran-basierten Graphenen und potenzielle Bausteine für porçse kovalente organische Gerüste dar.…”