Dreikernige Dithiadiaza[3.3.2]cyclophan‐ene

Schmiegel, Jürgen; Funke, Ulrike; Mix, Andreas; Grützmacher, Hans‐Friedrich

doi:10.1002/cber.19901230632

Cited by 6 publications

(6 citation statements)

References 8 publications

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“…The cyclization of dibromo compound 94 with 1,3-phenylenedimethanethiol derivatives and 1,4-phenylenedimethanethiol derivatives is literature known. [314] The cyclized product was obtained by a nucleophilic substitution reaction with potassium carbonate and 18-crown-6 in refluxing benzene. Even so the nucleophile was much more flexible this protocol seemed promising, since also two substitutions had to take place at the same time in order to form the desired macrocyclic structure.…”

Section: The Cyclization Reactionmentioning

confidence: 99%

“…For a first attempt the literature known protocol [314] was applied to form macrocycle 113, but since it ended in extensive polymer formation instead of macrocyclization, different reaction conditions had to be tested, which are listed in Table 9. The different tested conditions clearly indicated the dependency on the solvent and the reaction temperature.…”

Section: The Cyclization Reactionmentioning

confidence: 99%

“…In a first attempt the literature known protocol [314] was applied and the sulfur compound was almost instantly consumed, due to disulfide formation of the starting material 112. Therefore all subsequent reaction mixtures were degassed for at least 15 minutes with argon prior the addition of the sulfur functionalized biphenyl 112.…”

Section: The Cyclization Reactionmentioning

confidence: 99%

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Shape‐Switchable Azo‐Macrocycles

et al. 2009

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The synthesis of four shape‐switchable macrocycles comprising different peripheral substituents is described. The macrocycles 1–4 consist of m‐terphenyl semicircles interlinked by two azo joints. These macrocycles were assembled from nitro‐functionalized m‐terphenyl moieties through reductive dimerization. The semicircles were assembled through Suzuki cross‐coupling reactions. The molecular weights of the macrocycles were determined by vapour pressure osmometry, because mass spectrometry failed in the cases of 2 and 3. The E → Z photoisomerization reactions were analysed by UV/Vis spectroscopy complemented by 1H NMR studies. A very slow thermal back‐reaction indicated considerable stabilization of the Z isomer. The reduced efficiency of the thermal back‐reaction probably arises from the reduced degree of freedom due to the mechanical interlinking of the two azo groups. The photostationary state consisted of all‐Z (85 %) and all‐E isomers (15 %). The E → Z transformation induced by irradiation displayed simple exponential kinetics, which indicates pairwise switching of the two azo groups in a macrocycle, at least on the timescale under investigation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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Section: The Cyclization Reactionmentioning

confidence: 99%

Section: The Cyclization Reactionmentioning

confidence: 99%

Section: The Cyclization Reactionmentioning

confidence: 99%

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Shape‐Switchable Azo‐Macrocycles

et al. 2009

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“…(6) Backbone substitution. On first inspection, substitution along the ligand backbone would seem to cause potentially severe intraligand and ligand-R 2 N interactions in the dimers (11), in turn promoting monomers formation (12). However, it is difficult to assess the analogous interactions arising in the monomers.…”

Section: Discussionmentioning

confidence: 99%

“…The gem-dimethyl effect results when destabilizing interactions caused by substitution in an acyclic forms geminal dimethylation, for examplesare alleviated by ring closure (eq 2). [8][9][10][11] The cyclic transition structures often lead to newly formed carbocyclic or heterocyclic rings 12 but can be fleeting cyclic transition structures en route to acyclic products. 13 The substituent-dependent accelerations can be pronounced (up to 10 4 ).…”

Section: Introductionmentioning

confidence: 99%

Hemilabile Ligands in Organolithium Chemistry: Substituent Effects on Lithium Ion Chelation

2003

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The lithium diisopropylamide-mediated 1,2-elimination of 1-bromocyclooctene to provide cyclooctyne is investigated using approximately 50 potentially hemilabile polyethers and amino ethers. Rate laws for selected ligands reveal chelated monomer-based pathways. The dependence of the rates on ligand structure shows that anticipated rate accelerations based on the gem-dimethyl effect are nonexistent and that substituents generally retard the reaction. With the aid of semiempirical and DFT computational studies, the factors influencing chelation are discussed. It seems that severe buttressing within chelates of the substitutionally rich ligands precludes a net stabilization of the chelates relative to nonchelated (eta(1)-solvated) forms. One ligand-MeOCH(2)CH(2)NMe(2)-appears to promote elimination uniquely by a higher-coordinate monomer-based pathway.

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A macrocyclic 2,19‐dioxo[3.3](3,3′) azobenzolophane by transition‐metal carbonyl complex‐mediated CO insertion and cyclization

Schmiegel

Grützmacher

1990

Chem. Ber.

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2,19-Dioxo(3.3](3,3')azobenzolophane (5) has been obtained in a total yield of 18% by way of CO insertion and cyclization of 1,2-bis[3-(bromomethyl)phenyl]-4,4-dimethyl-3,5-pyrazolidinedione (1) using C O~( C O )~ in acetonitrile followed by the removal of the N-protecting 4,4-dimethylmalonyl groups. 5 is obtained predominantly as the transltrans isomer 5a and can be isomerized by irradiation with h = 369 nm to a mixture of nearly equal amounts of the transltrans, cis/ trans, and cis/cis isomers 5a, 5b, and 5c. The thermal isomerization back to 5a is slow but fast upon irradiation with h. = 443 nm.Medium and macrocyclic cyclophanes are routinely prepared from open-chain precursors by cyclization involving nucleophilic substitution'). In particular the reaction between sulfides and benzyl halides can be used for an efficient cyclophane synthesis. We have used this method in combination with the rigid-group principle2) and with high dilution techniques3) for the synthesis of a series of diazacyclophanes4) containing an azobenzene moiety, but up to now all attempts to effect a sulfur extrusion from these thia-and dithiadiazacyclophanes failed ' ). The macrocyclic azobenzolophanes undergo an interesting cisltrans photoisomerism which affects the shape of the molecular cavity, and the synthesis of azobenzolophanes lacking the weak benzylic C -S bond would be of some advantage for photochemical experiments. However, the synthesis of sulfur-free diazacyclophanes by a cyclization and a C -C bond formation by nucleophilic substitution') has not been successful ' ). The reductive coupling of benzyl halides using various low-valent metals represents an elegant method of a C-C bond formation'). However, attempts to use these methods for the preparation of cyclophanes from 1,3-bis[4-(brommethyl)-phenyllpropane used as a model compound have failed although good yields have been obtained for the coupling of benzyl bromide under the same reaction conditions'). This agrees with the results recently published by Wey and Butenschon8).Transition-metal carbonyl complexes are known to catalyze the intermolecular formation of carbon -carbon bonds by CO insertion into carbon -halogen bondsg). By treatment of dihalides with these reagents an insertion of CO and the intramolecular formation of small cyclic ketones (n = 5 -7) occur'o). However, again no cyclic products are obtained in a reaction of 1,3-bis[4-(brommethyl)phenyl]propane with Ni(CO), or COZ(CO)~ under various reaction conditions". Instead, the corresponding carboxylic acids are formed by the known sequence of CO insertion and hydrolytic cleavage of the metal -carbon bonds6). Apparently, CO insertion and cyclization require a rather special stereochemistry of the organic dihalide. Therefore, we have tried a combination of the rigid-group principle and the CO insertion method to prepare sulfur-free diazacyclophanes by using 1,2-bis[4-(brommethyl)phenyl]-4,4-dimethyl-3,5-pyrazolidinedione and 1,2-bis[3-(brommethyl)phenyl]-4,4-dimethyl-3,5-pyrazolidinedione (l), respectively, w...

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Dreikernige Dithiadiaza[3.3.2]cyclophan‐ene

Cited by 6 publications

References 8 publications

Shape‐Switchable Azo‐Macrocycles

Shape‐Switchable Azo‐Macrocycles

Hemilabile Ligands in Organolithium Chemistry: Substituent Effects on Lithium Ion Chelation

A macrocyclic 2,19‐dioxo[3.3](3,3′) azobenzolophane by transition‐metal carbonyl complex‐mediated CO insertion and cyclization

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