Condensed Cyclobutane Aromatic Compounds. X. Naphtho[b]cyclobutene

Cava, Michael P.; Shirley, R. L.; Erickson, Bruce W.

doi:10.1021/ja01488a039

Cited by 68 publications

(19 citation statements)

References 1 publication

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“…Since the aromaticity of both rings has to be given up in o-naphthoquinodimethane (6), this intermediate is certainly less stable, and hence more reactive, than the corresponding o-quinodimethane derivative (generated from bis(dibromomethyl)benzene under similar conditions). [19][20][21] Evidently the bimolecular Diels-Alder reaction (which is limited in its rate by diffusion) cannot compete with the intramolecular electrocyclization in the case of 6.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Supramolecular Properties of Molecular Clips with Anthracene Sidewalls

Klärner¹,

Kahlert²,

Boese³

et al. 2005

Chemistry A European J

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Novel molecular clips with anthracene sidewalls (1 a-c) were synthesized; they form stable host-guest complexes with a variety of electron-deficient aromatic and quinoid molecules. According to single-crystal structure analyses of clip 1 c and 1,2,4,5-tetracyanobenzene (TCNB) complex 14@1 b, the clips' anthracene sidewalls have to be compressed substantially during the complex formation to provide attractive pi-pi interactions between the aromatic guest molecule and the two anthracene sidewalls in the complex. The compression and expansion of aromatic sidewalls are calculated by molecular mechanics to be low-energy processes, so the energy required for compression of the anthracene sidewalls during complex formation is apparently overcompensated by the gain in energy resulting from the attractive pi-pi interactions. The finding that complexes of the clips 1 a-c are more stable than those of the corresponding clips 2 a-c can be explained in terms of the larger van der Waals contact surfaces of the anthracene sidewalls in 1 a-c (relative to the naphthalene sidewalls in 2 a-c). Color changes resulting from charge-transfer (CT) bands are observed in complex formation by 1 a-c: from colorless to red or purple with TCNB (14), and from yellow to green with 2,4,7-trinitro-9-fluorenone TNF (17). Independently, the host 1 b and guest 14 fluoresce from their respective excited singlet states, whilst in the complex 14@1 b the charge-transfer state quenches the higher-energy singlet states of the two components, and as a result luminescence is only observed from this new CT state. To the best of our knowledge, complex 14@1 b is the first example of CT luminescence from a host-guest complex. The binding constant determined for the formation of the TCNB complex 14@1 b from a UV/Vis titration experiment (Ka = 12 400 m(-1)) agrees well with the value (K(a) = 12 800 m(-1)) obtained by 1H NMR titration.

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Section: Resultsmentioning

confidence: 99%

Synthesis and Supramolecular Properties of Molecular Clips with Anthracene Sidewalls

Klärner¹,

Kahlert²,

Boese³

et al. 2005

Chemistry A European J

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“…Crystals of naphtho [b]cyclobutene, which was first synthesized by Cava & Shirley (1960), were supplied by Dr Ashley Cooper of the Jet Propulsion Laboratory, Pasadena. They were colorless prisms, somewhat elongated along a.…”

Section: Methodsmentioning

confidence: 99%

“…Preliminary rotation and Weissenberg photographs showed monoclinic symmetry with systematic absences (hOl, l odd; 0k0, k odd) characteristic of space group P21/c. The crystal was then mounted on a General Electric quarter-circle diffractometer, automated by Datex and highly modi- 86°C * Z=4 F(O00) = 328 D~= 1"23 gcm -a /a=4 cm -' 2(Cu Ks)= 1"5418/~, * Cava & Shirley (1960).…”

Section: Methodsmentioning

confidence: 99%

The crystal structure of naphtho[b]cyclobutene

Crawford¹,

Marsh²

1973

Acta Crystallogr Sect B

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“…The first synthesis of 19 starts with the in situ generation of dibromo-o-quinodimethane 12 by 1,4-Br 2 elimination from tetrabromo-o-xylene 11 with sodium iodide as nucleophile (Scheme 2). This reaction has been already described by Cava et al in 1960. [27] In the absence of a trapping reagent, the highly reactive o-quinodimethane derivative 12 undergoes an electrocyclic ring closure yielding 3,4-dibromo-1,2-benzocyclobutene, which can also be used as a precursor in the preparation of 12 at higher temperature (150 8C).…”

Section: Resultsmentioning

confidence: 85%

Synthesis and Supramolecular Properties of Trimethylene‐Bridged Clips

Klärner¹,

Lobert²,

Naatz³

et al. 2003

Chemistry A European J

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The novel trimethylene-bridged clips 3 and 4 have been synthesized by using repetitive stereoselective Diels-Alder reactions of the benzo- and naphthobismethylenenorbornenes 8 and 19 as dienes and norbornadiene 9 as bisdienophile, and subsequent dehydrogenation of the primary cyclobisadducts 10 and 20 by using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Clips 3 and 4 serve as receptors for a variety of electron-deficient neutral and cationic aromatic substrates, comparable to the molecular tweezers 1 and 2. The thermodynamic parameters of the complex formation, K(a) and DeltaG, were determined by (1)H NMR titration experiments and, in the case of the highly stable complex TCNB 32@4, by the use of isothermal titration microcalorimetry. The finding that clip 4 forms more stable complexes than 3 can be explained by the larger van der Waals contact surfaces of the naphthalene sidewalls in 4 compared to the corresponding benzene systems in 3. In the complexes with 4 as receptor, the plane of each aromatic substrate molecule is calculated to be oriented almost parallel to the naphthalene sidewalls. However, in the complexes of tweezers 2, the substrate is usually oriented parallel to the central naphthalene spacer unit. Due to the more open topology of 4, most complexes were calculated to consist of two or more equilibrating noncovalent conformers.

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Condensed Cyclobutane Aromatic Compounds. X. Naphtho[b]cyclobutene

Cited by 68 publications

References 1 publication

Synthesis and Supramolecular Properties of Molecular Clips with Anthracene Sidewalls

Synthesis and Supramolecular Properties of Molecular Clips with Anthracene Sidewalls

The crystal structure of naphtho[b]cyclobutene

Synthesis and Supramolecular Properties of Trimethylene‐Bridged Clips

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