Facile Aromatization Reactions of Overcrowded Polycyclic Aromatic Enes Leading to Fullerene Fragments

Pogodin, Sergey; Biedermann, P. Ulrich; Agranat, Israel

doi:10.1021/jo9700991

Cited by 33 publications

(17 citation statements)

References 21 publications

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“…We have recently reported a facile synthesis of benzo[e]indeno[1,2,3-hi ]-acephenanthrylene (4) and its 1-chloro derivative by homogenous reductive cyclodechlorination and cyclodehydrochlorination of (E )-and (Z )-1,1 -dichlorobi-9H -fluoren-9-ylidene (5), using palladium acetate [14]. We note that 4 was a fullerene fragment which was not a buckybowl.…”

Section: Introductionmentioning

confidence: 99%

Stereochemistry of ( E )- and ( Z )-1,1′-Dichlorobifluorenylidenes, Substituted Overcrowded Fullerene Fragments

Pogodin

Cohen²,

Biedermann³

et al. 2002

Enantiomer

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X-ray crystallographic and semiempirical PM3 and AM1 studies of 1,1'-dichlorobi-9H-fluoren-9-ylidene (5) are reported. The X-ray molecular structure of (Z)-5 indicated an approximately C2 symmetric conformation with pure twist around C9 = C9' of 40.4 degrees. The fjord regions are somewhat overcrowded: r(C8...C8') = 315.3 pm, r(Cl(1)...Cl(1') = 341.7 pm, r(C(8)...H(8')) = 259.0 pm. The four chlorine atoms of two neighboring molecules of (Z)-5 form a chain. The PM3 calculations showed that the global minimum of 5 is the C2 symmetric twisted conformation t(E)-5, which is 2.4 kJ/mol more stable than its diastereomer C2-t(Z)-5. The corresponding AM1 relative stability is reversed: C2-t(Z)-5 is 1.1 kJ/mol more stable than C2-t(E)-5. The pure twists of t(Z)-5 and t(E)-5 are 37.0 degrees and 37.2 degrees (PM3) and 40.5 degrees and 39.1 degrees (AM1). The corresponding (E) --> (Z) (PM3) and (Z) --> (E) (AM1) energy barriers of diastereomerization are 80.6 kJ/mol (PM3) and 75.8 kJ/mol (AM1). Two anti-folded local minima conformations C2-a(Z)-5 and C(i)-a(E)-5 were found to be 21.2 and 29.5 kJ/mol (PM3) and 25.8 and 35.2 kJ/mol (AM1) less stable than t(E)-5. The syn-folded conformations C(S)-s(Z)-5 and C2-s(E)-5 are transition states for the enantiomerization processes of C2-tz-5 and C2-tE-5, respectively, and lay 79.8 and 94.1 kJ/mol (PM3) and 108.3 and 107.4 kJ/mol (AM1) higher in energy than their corresponding twisted conformations. An alternative pathway for enantiomerization of C2-t(E)-5 via the anti-folded achiral intermediate C(i)-a(E) has a barrier of 56.0 kJ/mol (PM3) and 68.5 (AM1). An alternative pathway for enantiomerization of C2-t(Z)-5 via C2-t(E) and C(i)-a(E) has a barrier of 80.6 (PM3) and 75.8 (AM1) kJ/mol.

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Section: Introductionmentioning

confidence: 99%

Stereochemistry of ( E )- and ( Z )-1,1′-Dichlorobifluorenylidenes, Substituted Overcrowded Fullerene Fragments

Pogodin

Cohen²,

Biedermann³

et al. 2002

Enantiomer

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“…6 Single crystals of the pure (Z) diastereomer of 1,1'dichloro-bifluorenylidene were obtained by recrystallization of the mixture of the (E)-and (Z)-diastereomers. 25,26 In the present case of DMXA, the unexpected finding that it had crystallized only as the pure (E)-diastereomer enabled us to study its E,Z-diastereomerization over a wide range of temperatures that ensured reliable values of the free energy of activation (ΔG c # ) for the process. A preliminary crystal structure of xanthylidene-anthrone (XA) was reported in 1954.…”

Section: Resultsmentioning

confidence: 96%

Heteromerous Bistricyclic Aromatic Enes: Dynamic Stereochemistry of Xanthylidene‐Anthrones

et al. 2015

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The heteromerous bistricyclic aromatic ene (BAE) 2,2'-dimethyl-10-(9H-xanthylidene)-9(10H)-anthrone (DMXA) was synthesized by a condensation of 10,10-dichloro-2-methylxanthene with 2-methylanthrone. X-ray crystallography of (E)-DMXA and xanthylidene-anthrone (XA) indicated that the molecules adopt anti-folded conformations with folding dihedral angles of 44°/44° and 39°/41°, respectively. The crystal structure of anti-folded (E)-DMXA does not indicate any xanthenylium-anthracenolate push-pull effect. E,Z-diastereomerization of DMXA was studied by (1) H-NMR coalescence-temperature measurements at different magnetic field strengths and by kinetic equilibration experiments. Free energy of activation for this process was 81.5 (±1.3) kJ/mol. B3LYP/6-311+G(d,p) calculations showed that anti-folded conformers of XA, (E)-DMXA, bianthrone (AA), and dixanthylene (XX) were global minima. The twisted conformers of XA, AA, and XX were local minima (ΔG298 = 16, 18, and 24 kJ/mol) with a substantial dipolar xanthenylium-anthracenolate dipolar contribution for XA. Chirality 27:919-928, 2015. © 2015 Wiley Periodicals, Inc.

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“…For example, 1 may react with electrophiles at the periphery as a conventional PAHs to give a product of S E Ar; alternatively, it also reacts in fullerene‐like (olefin) fashion with both nucleophiles and electrophiles through addition to the central double bond . Although 1 appears as an easy target molecule, there are only two currently published approaches allowing for its synthesis (Figure ) . The first has been reported by Scott and co‐workers, in which the flash vacuum pyrolysis approach was employed.…”

Section: Figurementioning

confidence: 99%

“…[1,17] Although 1 appearsasaneasy target molecule, there are only two currently publisheda pproaches allowing for its synthesis (Figure 1). [18][19][20][21][22] The first has been reported by Scott and coworkers, in which the flash vacuum pyrolysis approach was employed.A notherk nown pathway is based on intramolecular Pd-catalyzed aryl-arylc oupling. Both methods have some severel imitations, including low overall yields and moderate yields at the last step.…”

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confidence: 99%

Tailoring Diindenochrysene through Intramolecular Multi‐Assemblies by C−F Bond Activation on Aluminum Oxide

Akhmetov

Feofanov

Troyanov

et al. 2019

Chemistry A European J

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Facile Aromatization Reactions of Overcrowded Polycyclic Aromatic Enes Leading to Fullerene Fragments

Cited by 33 publications

References 21 publications

Stereochemistry of ( E )- and ( Z )-1,1′-Dichlorobifluorenylidenes, Substituted Overcrowded Fullerene Fragments

Stereochemistry of ( E )- and ( Z )-1,1′-Dichlorobifluorenylidenes, Substituted Overcrowded Fullerene Fragments

Heteromerous Bistricyclic Aromatic Enes: Dynamic Stereochemistry of Xanthylidene‐Anthrones

Tailoring Diindenochrysene through Intramolecular Multi‐Assemblies by C−F Bond Activation on Aluminum Oxide

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