Generalization of the triptycene concept. Use of diaryne equivalents in the synthesis of iptycenes

Hart, Harold; Shamouilian, Shamouil; Takehira, Yoshikazu

doi:10.1021/jo00335a021

Cited by 111 publications

(80 citation statements)

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“…4 In 1981, H. Hart optimized the reaction conditions for the synthesis of heptiptycene 1, obtaining a reproducible 20% yield, and demonstrated that the cyclotrimerization occurs through a strained alkyne intermediate, which was trapped during the reaction. 5 In a first attempt to improve the yields of the cyclotrimerization of 2,3-dibromobicyclo[2.2.2]oct-2-ene, K. Komatsu introduced nickel(0) to stabilize the alkyne intermediate, although finally the role of the metal resulted negligible. 6 An important progress in the synthesis of BCTs has been the use of copper(I), which causes a copperÀlithium exchange, leading to improved chemo-selectivity, presumably avoiding the alkyne intermediate.…”

Section: Benzocyclotrimers: Synthesismentioning

confidence: 99%

Benzocyclotrimers: From the Mills−Nixon Effect to Gas Hosting

et al. 2011

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The formal annulation of three bicylic olefins yields a class of molecules termed benzocyclotrimers (BCTs), which have unusual electronic properties. The bonds in the central aromatic ring, for example, alternate in length: rather than resembling a substituted benzene, a BCT instead evokes comparison to a cyclohexatriene. Forty years have passed since the synthesis of heptiptycene, the first BCT, was reported. In the interim, many methods have been developed for preparing tris-bicycloannulated benzenes. More than thirty different BCTs have so far been reported, with a variety of morphological features and properties. Over the same period, yields have increased from just a few percent to almost quantitative conversion. This improvement in synthetic access has expanded interest beyond the original theoretical considerations (bond-length fixation in aromatics) to functional applications (supramolecular scaffolds). In this Account, we describe the evolution of synthetic approaches to BCTs and their derivatives, as well as the applications that are now being explored for these compounds. Early syntheses of BCTs involved chloroolefins treated with butyl lithium. A strained alkyne intermediate was postulated early on, and was indeed trapped in 1981. Subsequent efforts have focused on improving chemoselectivity by mitigating the drastic conditions required for the generation of the alkyne intermediate. Our introduction of Cu(I) to induce lithium-copper exchange was successful in this regard. Further improvement resulted from the use of bicylic bromo(trimethylstannyl)olefins. In an effort to avoid the toxicity of the tin reagents, the Heck reaction and Pd catalysis have been pursued for cyclotrimerizing bicylic bromo- and iodoolefins. Depending on the symmetry of the starting bicylic olefin, two diastereomers can be obtained in the preparation of a BCT: a syn compound with C(3) symmetry and an anti compound with C(s) symmetry. Studying the diastereomeric outcome in a variety of synthetic approaches has yielded valuable insight into the cyclotrimerization reaction. Moreover, highly symmetric compounds, such as a D(3)-symmetric trindane and C(3v)-symmetric sumanene, have been prepared as BCT derivatives. The structure of BCTs offers a versatile three-dimensional scaffold for studying molecular recognition. Like calixarenes, BCTs form complexes with a variety of guest molecules. Recent developments include the trapping of gases in a hydrogen-bonded dimer and the encapsulation of larger molecules within a covalently linked condensation derivative. Future innovations in this fertile research area will likely include highly functionalized curved aromatics, receptors, and sensors.

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Section: Benzocyclotrimers: Synthesismentioning

confidence: 99%

Benzocyclotrimers: From the Mills−Nixon Effect to Gas Hosting

et al. 2011

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“…',C-NMR (90.6 MHz, CDCI,): 59.09; 60. 15;123.25;123.26;125.45;125.47;125.63;140.49;143.35;318,320 (16,19,6 M+), 237, 239 (77, 31, Bis[(trimethylsilyl)ethynyl]-Y,l0-dihydro-Y,IO-ethenoanthracene (11). To a degassed soln.…”

Section: Ii-bro~no-i2-ehloro-yiu-cli/zydro-9iu-cthtnoanf/irucene (mentioning

confidence: 99%

“…The synthesis of 5 (Scheme 2) starts with the Diels-Alder reaction of anthracene and trans-dichloroethene to give 8 [ 141. Subsequent dehydrochlorination to the 9,lO-ethenoanthracene 9 was accomplished with t -BuOK [15]. The bromination to 10 was best achieved by simply adding elemental Br, to a solution of the vinyl anion at -78".…”

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confidence: 99%

Synthetic Routes to the Cyclo[n]carbons

Diederich¹,

Rubin

Chapman

et al. 1994

Helvetica Chimica Acta

117

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Cyclo[n]carbons (cyclo-C,) are n-membered monocyclic rings of sp-hybridized C-atoms with unique electronic structures resulting from two perpendicular systems of conjugated n-orbitals, one in-plane and one out-ofplane. Several synthetic approaches to generate cyclo-Clx from stable precursors were investigated. In a six-step sequence from anthracene, tris(anthraceno)hexadehydro[l8]annulene 5 was prepared and shown by laser-desorption time-of-flight mass spectrometry to generate C,, in three successive retro-Diels-Alder reactions, together with anthracene as the by-product. The attempted preparation of CIS by flash-vacuum pyrolysis of 5 using solventassisted sublimation only afforded anthracene next to polymers. The reaction of 1,6-bis(triisopropylsilyl)hexa-1,3,5-triyne with [Co,(CO),] followed by exchange of two CO groups for a bridging bis(dipheny1phos-phino)methane (dppm) ligand gave Co complex 22 which, after removal of the silyl groups, was oxidatively cyclized to afford the very stable trimeric and tetrameric macrocycles 6 and 7, complexes with cyclo-C,, and cyclo-C,,, respectively. An X-ray crystal structure established the identity of 6 and showed that the butadiyne units within the C,, core are considerably bent. Attempts to free cyclo-Clx from the coordinating metal atoms in 6 did not succeed, presumably due to the steric shielding of the Co-atoms by the dppm ligands. Low-temperature matrix isolation studies using IR and UVjVIS spectroscopy showed that irradiation of carbon oxide 2 (C&06) leads to ketene intermediates and, by subsequent loss of six CO molecules, presumably to cyclo-C,,.

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“…Fullerene is a constituent unit for constructing such hybrid materials. Polymerized fullerenes can form one-, two-, and three-dimensional covalent networks depending on the fullerene cages and the arrangements of the sp 3 C atoms, yielding metallic and semiconducting electronic structures [15][16][17] [18][19][20][21][22][23][24][25][26]. In these molecules, three (poly)acenes (sp 2 C units) are adjoined via two sp 3 C atoms situated at their molecular axes.…”

Section: Introductionmentioning

confidence: 99%

Magnetic properties of two-dimensional hydrocarbon networks of sp2 and sp3 C atoms

Sorimachi

Okada

2017

Phys. Rev. B

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Based on first principles total energy calculations, we investigate geometric, electronic, and spin structures in two-dimensional polyacene-based hydrocarbon networks of sp 2 and sp 3 C atoms. Polyacenes connecting adjacent sp 3 atoms form kagome networks. The networks are stable and retain their covalent topologies up to 2000 K. They possess kagome flatbands at or near the Fermi level, depending on the size and structure of the polyacene adjoining the sp 3 C atoms. We find that the spin states of the two-dimensional covalent hydrocarbon network are changeable from antiferromagnetic to ferromagnetic by increasing the length of the sp 2 C region.

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Generalization of the triptycene concept. Use of diaryne equivalents in the synthesis of iptycenes

Abstract: Hz separation) and at 1.08 and 1.21 34.1-Hz separation) was 30% ee.35 Since the aldehyde sample had [a]MD -9.24°(c 4.5, CgHg), the rotation for the enantiomerically pure aldehyde is [a]20]) -30.8 ± Io (c 4.5, CgHg). Asymmetric hydroformylation results are summarized in Table II.

Cited by 111 publications

References 1 publication

Benzocyclotrimers: From the Mills−Nixon Effect to Gas Hosting

Benzocyclotrimers: From the Mills−Nixon Effect to Gas Hosting

Synthetic Routes to the Cyclo[n]carbons

Magnetic properties of two-dimensional hydrocarbon networks of sp2 and sp3 C atoms

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