Synthesis and Electronic Properties of Fluoreno[2,1-a]fluorenedione and Fluoreno[1,2-a]fluorenedione

Abstract

The [2,1-a]- and [1,2-a]-isomers of fluorenofluorenedione have been synthesized via intramolecular Friedel-Crafts acylations. DFT calculations indicate that the [1,2-a]-isomer adopts a twisted, helical C-symmetric structure and that its protonated form is the thermodynamic product of the Friedel-Crafts acylation in hot sulfuric acid. Absorption spectroscopy and cyclic voltammetry measurements provide experimental estimations of frontier molecular orbital energy levels, which are reported and discussed.

Oxidative Photocyclization of Aromatic Schiff Bases in Synthesis of Phenanthridines and Other Aza-PAHs

“…Commercially available reagent-grade materials were used as obtained from Sigma-Aldrich, Acros Organics, Apollo Scientific, and Fluorochem. Bromoarenes 7o [ 45 ] , 7p [ 46 ] , 8b [ 42 ] and bis-triflate 8a [ 47 ] were prepared according to published procedures. All solvents (Lach-Ner) were of a reagent grade and used without any further purification, except for tetrahydrofuran and toluene, which were distilled from sodium benzophenone ketyl, and dichloromethane, which was distilled from calcium hydride.…”

Intermolecular Three-Component Synthesis of Fluorene Derivatives by a Rhodium-Catalyzed Stitching Reaction/Remote Nucleophilic Substitution Sequence

“…Furthermore, some fluorenes having a heteroatom substituent at their bridging carbon (9-position) are known to exhibit biological activity . Because of the high utility of this structural motif, various synthetic methods of fluorenes and their derivatives have been developed to date, but most of the existing methods rely on the use of intramolecular processes as exemplified in the classical Friedel–Crafts cyclization, radical cyclization, and more recent transition-metal-catalyzed cyclization involving C–H bond activation . With regard to the more desirable intermolecular processes in view of convergent nature and structural diversity, several approaches have been reported, including palladium-catalyzed tandem cross-coupling/cyclization reactions to give 9 H -fluorenones or 9-unsubstituted 9 H -fluorenes, palladium-catalyzed methylenation reactions of 2-halobiaryls to give 9-unsubstituted 9 H -fluorenes or 9,9-disubstituted 9 H -fluorenes, and Brønsted acid-catalyzed three-component reactions to give 11-methoxy-11-aryl-11 H -benzo­[ a ]­fluorenes .…”

Directed Ortho and Remote Metalation of Naphthalene 1,8-Diamide: Complementing SEAr Reactivity for the Synthesis of Substituted Naphthalenes

“…Recently, Frantz reported the synthesis of fluoreno[1,2α]fluorenedione (12), as well as the linear isomeric fluoreno-[2,1-α]fluorenedione, using double intramolecular Friedel− Crafts cyclization reactions. 62 The fluorene-dione 12 (Scheme 2) was obtained in 89% yield using hot sulfuric acid. In THF solvent, the reaction 11 → 12 has a corresponding B3LYP-XDM free energy penalty of 7.7 kcal/mol, similar to that seen for 9 → 12.…”

“…Frantz argued that strong acid was needed to stabilize compound 12 and the corresponding protonated transition state interspersed in the sequence 10 → 12. Calculations at the B3LYP/6-31G* level 62 indicate that the sterically hindered difluorenone 12 has a ground-state energy that is 13.4 kcal/mol higher than the unhindered [2,3-b] isomer. 62 For comparison, our B3LYP-XDM calculations predict this relative energy difference to be 12.0 kcal/mol, which is in fairly close agreement with the previous theoretical value.…”

“…Calculations at the B3LYP/6-31G* level 62 indicate that the sterically hindered difluorenone 12 has a ground-state energy that is 13.4 kcal/mol higher than the unhindered [2,3-b] isomer. 62 For comparison, our B3LYP-XDM calculations predict this relative energy difference to be 12.0 kcal/mol, which is in fairly close agreement with the previous theoretical value. Franz proposed that compound 12 adopts a "twisted, helical C 2 -symmetric structure to accommodate steric clashing, and likely electrostatic repulsion, of the two oxygen atoms" and suggested, also based on calculations, that a protonated form (proton squeezed between the two carbonyls) is the thermodynamically controlled product.…”