Synthesis of polymethyl substituted [2.2]metaparacyclophanes and their Lewis-acid induced isomerisation to [2.2]metacyclophanes

Shimizu, Tomoe; Hita, Katsuhiro; Paudel, Arjun; Tanaka, Junpei; Yamato, Takehiko

doi:10.3184/030823409x430185

Cited by 5 publications

(3 citation statements)

References 22 publications

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“…The preparative route of 8-bromomethyl[2.2]MPCP 2 is shown in Scheme 2 following our previous reported procedure. 15,16 Thus bromination of 1 14,[17][18][19][20][21] with N-bromosucccinimide (NBS) in the presence of benzoyl peroxide under CCl 4 reflux for 3 h afforded the desired 8-bromomethy[2.2]MPCP 2 in 90% yield.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Structures of 8-Benzyl[2.2]Metaparacyclophanes

Sharma

Shinoda

Miyamoto

et al. 2010

Journal of Chemical Research

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A convenient preparation of 8-benzyl[2.2]metaparacyclophanes using TiCl 4 catalysed Friedel-Crafts benzylation of arenes with 8-bromomethyl[2.2]metaparacyclophane is described. The structures of these novel 8-benzyl[2.2]metaparacyclophanes in solution are also discussed. [2.2]MPCP ([2.2]metaparacyclophane) was first prepared 1 via acid-catalysed rearrangement of [2.2]paracyclophane. Since then, [2.2] of MPCP has been prepared by other synthetic methods. 2-9 A versatile procedure, appropriate for the synthesis of substituted derivatives, makes use of 2,11-dithia[3.3]MPCP as a precursor. 3 The meta-bridged benzene ring of [2.2]MPCPhas been shown to undergo conformational flipping 2,3,6,8,10-12 with a substantial energy barrier (ca 80 kJ mol -1 ), so that elevated temperatures (about 400 K) were required for the interconversion to be revealed on NMR time scale. A large part of this energy barrier is believed to arise from steric destabilisation of the transition state in which the 8-hydrogen atom of the meta-bridged ring impinges into the π-electron cloud of the para-bridged one.According to X-ray crystallographic studies of [2.2]MPCP, 13 the deformations of benzene rings in [2.2]MPCP are similar to those of the corresponding rings in [2.2]para-and [2.2]metacyclophane, with para-and meta-bridged rings bent in a boatand a chair-like form, respectively. The angle between the two aromatic planes defined by the carbon atoms, 3, 4, 6, and 7, on one hand, and 12, 13, 15, and 16, on the other, is about 13°. Note that the angle between the 11, 12, 16-plane and 10, 11bond vector (or between 13, 14, 15-plane and 1, 14-bond vector) is even larger than the analogous angle in [2.2]paracyclophane. The para-briged moiety of [2.2]MPCP is thus more strongly tilted than those of the isomeric compound. The rotation of the methyl group (which is fixed above the parabenzene ring) of 8-methyl[2.2]MPCP appears to be hindered, if not blocked. However, proton resonance measurements down to -20 °C show no rotation barrier for the molecule in solution. 14 Thus introduction of methyl substituted benzyl groups to the 8-position of [2.2] of MPCP might increase the rotation barrier around the [2.2]MPCP-CH 2 -Ar for the molecule in solution. It is surprising that there have been no reports on the preparation of 8-(methyl substituted benzyl)[2.2]MCPs despite the fact that the chemical shift of the 2, 3, and 4-methyl substituent provides a convenient probe for 1 H NMR studies of any possible conformational changes. There has been substantial interest in investigating the structures of 8-(methyl substituted benzyl)[2.2]MPCPs. We report here the convenient * Correspondent.

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Section: Resultsmentioning

confidence: 99%

Synthesis and Structures of 8-Benzyl[2.2]Metaparacyclophanes

Sharma

Shinoda

Miyamoto

et al. 2010

Journal of Chemical Research

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“…Only a single Scheme 1: Nitration of [2.2]paracyclophane (1) and the synthesis of 4-hydroxy-5-nitro [2.2]metaparacyclophane (5) and the cyclohexadienone cyclophane 6 (average yield from more than three repeats quoted). group regularly publishes in this area [24][25][26][27][28][29][30][31]. Yet [2.2]metaparacyclophane (3) has a fascinating structure that mix the characteristics of both meta-and paracyclophane [32].…”

Section: Introductionmentioning

confidence: 99%

Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

Patel¹,

Dais²,

Plieger³

et al. 2021

Beilstein J. Org. Chem.

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Substituted [2.2]metaparacyclophanes are amongst the least studied of the simple cyclophanes. This is undoubtedly the result of the lengthy syntheses of these compounds. We report the simple synthesis of a rare example of a non-symmetric [2.2]metaparacyclophane. Treatment of [2.2]paracyclophane under standard nitration conditions gives a mixture of 4-nitro[2.2]paracyclophane, 4-hydroxy-5-nitro[2.2]metaparacyclophane and a cyclohexadienone cyclophane.

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“…The most common connectivity patterns are those represented in [ m , n ]‐ meta , meta ‐cyclophanes 1 and [ m.n ]‐ para , para ‐cyclophanes 2 (Scheme ), and these are more commonly referred to as simply [ m.n ]‐ meta ‐cyclophanes and [ m.n ]‐ para ‐cyclophanes, respectively. Although [ m.n ]‐ meta , para ‐cyclophanes are known,3d,q they have been rarely studied compared to other [ m.n ]cyclophanes of which the most popular have been the [2.2]‐ para ‐cyclophanes 2. 3c Numerous methods have been developed for the synthesis of [ m.n ]cyclophanes 1–3.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of [m.n]Cyclophanes: Regiochemistry Transfer from Vinyl Halides to Cyclophanes via Fischer Carbene Complexes

Wang

Predeus

Wulff

2013

Chemistry A European J

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The double benzannulation of bis-carbene complexes of chromium with α,ω-diynes generates [m.n]cyclophanes in which all three rings are generated in a single reaction. This triple annulation process is very flexible allowing for the construction of symmetrical [n.n]cyclophanes and unsymmetrical [m.n]cyclophanes as well as isomers in which the two benzene rings are both meta bridged or both para bridged, and isomers that contain both meta and para bridges. The connectivity patterns of the bridges in the cyclophanes can be controlled by regioselectivity transfer from the bis-vinyl carbene complexes in which the substitution pattern of the vinyl groups in the carbene complexes dictate the connectivity pattern in the [m.n]cyclophanes. This synthesis of [n.n]cyclophanes is quite flexible with regard to ring size and can be used with tether lengths ranging from n=2 to n=16 and thus to ring sizes with up to 40 member rings. The only limitation to regioselectivity transfer from the carbene complexes to the [m.n]cyclophanes was found in the synthesis of para,para-cyclophanes with four carbon tethers for which the loss of fidelity occurred with the unexpected formation of meta,para-cyclophanes.

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Synthesis of polymethyl substituted [2.2]metaparacyclophanes and their Lewis-acid induced isomerisation to [2.2]metacyclophanes

Cited by 5 publications

References 22 publications

Synthesis and Structures of 8-Benzyl[2.2]Metaparacyclophanes

Synthesis and Structures of 8-Benzyl[2.2]Metaparacyclophanes

Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

Synthesis of [m.n]Cyclophanes: Regiochemistry Transfer from Vinyl Halides to Cyclophanes via Fischer Carbene Complexes

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