Structure, cyclophane-type

The reaction has been applied to the synthesis of cyclophane-type structures by use of dihaloarenes and Grignard reagents from a, w-dihalides. 

J.-P. Bourgeois, P. Seiler, M. Fibbioli, E. Pretsch, F. Diederich, L. Echegoyen, Cyclophane-Type Fullerene-dibenzo [18] crown-6 Conjugates with trans-1, trans-2, and trans-3 Addition Patterns Regioselective Templated Synthesis, X-ray Crystal Structure, Ionophoric Properties, and Cation-Complexation-Dependent Redox Behavior , Helv. Chim Acta 1999, 82,1572-1595. 

Very recently, nice recognition of free and AT-acetylated amino acids (Gly, Ala, Phe) and some structurally related guests by a dicationic cyclophane-type A/,Ar -dibenzylated chiral derivative (4) of a bisisoquinoline alkaloid S,S-(+)-tetrandine (3 DBT) has been studied by NMR titration in water [31]. In contrast to other macrocyclic hosts, DBT shows high affinity and large enan-tioselectivity (K(S)/K(R)> 10) toward the smaller N-acetylalanine and binds the larger phenylalanine more weakly and nonselectively. The binding specificity of DBT was rationalized on the basis of molecular mechanics calculations. 

Figure 3.1.5 Schematic Representation of the Cyclophane-type Structure of 3.36...

Schwabacher et al. (1972) prepared a cyclophane-type structure with metal ions coordinated into the walls of the macrocycle (70). This system was first reported in 1992 and shown to transport neutral aromatic hydrocarbons through an aqueous membrane. Even though this receptor has a net anionic charge, it has been illustrated to bind indole and naphthalene units functionalized with... 

Polyaza macrobicyclic cryptands synthesis, crystal structures of a cyclophane type macrobicyclic cryptand and of its dinuclear copper(I) cryptate, and anion binding features, J. Jazwinski, J.-M. Lehn, D. Lilienbaum, R. Ziessel, J. Guilhem and... 

Synthesis, crystal structure of a cyclophane type macrobicyclic cryptand and of its dinuclear copper(I) cryptate,... 

Bisbenzylisoquinoline alkaloids form a large group (>150) of naturally occurring compounds in which two benzylisoquinoline moieties are joined by up to three ether links. Many of them have macrocyclic cyclophane-type structures, which makes them potentially capable of forming inclusion compounds with small guests. In addition, they have several stereogenic centers and may be useful... 

Cyclotriveratrylene, by analogy with calixarenes, cyclodextrins and a few other cyclophane-type compounds, can be used as a matrix to preorganize coordination sites for transition metals, either at the edge of the rigid structure, or around an expanded CTV s cavity. Achiral 2- and 3-pyridine tripod ligands have been synthesized together with a bipyridine multichelate. Studies of these new ligands, both by... 

Harrowfield et al. [37-39] have described the structures of several dimethyl sulfoxide adducts of homo bimetallic complexes of rare earth metal cations with p-/e rt-butyl calix[8]arene and i /i-ferrocene derivatives of bridged calix[4]arenes. Ludwing et al. [40] described the solvent extraction behavior of three calixarene-type cyclophanes toward trivalent lanthanides La (Ln = La, Nd, Eu, Er, and Yb). By using p-tert-huty ca-lix[6Jarene hexacarboxylic acid, the lanthanides were extracted from the aqueous phase at pH 2-3.5. The ex-tractability is Nb, Eu > La > Er > Yb. 

In this section, various types of topochemical behaviour such as the even-numbered degree of polymerization mechanism, topochemical induction into the syndiotactic structure, stereo- and enantio-selective reactions, and the formation of highly strained cyclophanes are described. 

Another type of face-to-face-arrangement is found in the multi-layered annulene systems [ 14] and [15], Here, unlike the para-cyclophanes, in which the phenyl units are connected by external alkanediyl groups, the stacking of annulene layers is achieved by internal linkages, with the bridge located inside the 7t-clouds. The advantage of the latter structure is that one can... 

Cyclic thiourea derivatives having three different types of cyclophane structure (ortho-meta, meta-meta and meta-para) and a lariat-type thiourea have been synthesized, using reaction of isothiocyanate with amine.230 Cyclic thioureas have been obtained from formaldehyde aminals and sulfur (Sg) (Scheme 77).231... 

These structural data demonstrate that 12 is a rather less distorted molecule than [2.2]paracyclophane. However, a dramatic effect of the strong cr(Si—Si)—w interaction was observed in UV spectra as shown in Fig. 5. In the UV spectrum of phenylpentamethyldisilane, an intramolecular crfSi—Si)—7T charge-transfer band appears around 231 nm (11a, 12). Octamethyltetrasila[2.2]ortho- (15) and metacyclophane (16) show similar absorptions, but the band splits into two bands at 223 nm (e = 19,100) and 263 nm (e = 22,500) in 12. This type of red shift in the UV spectra occurs only in 12 among other polysilapara-cyclophanes such as 13 and 14. 

Lindner (171) developed his own tt-SCF MO force field that is similar to MMPI in construction. This program was applied to simulate racemization of metacyclophane (48) and hexahelicene (50). In metacyclophane the m-phenylene ring flips readily at room temperature. Two mechanisms can be conceived one operates by way of a high steric energy conformation (48b) the other involves a biradical intermediate (49). The calculated activation energies are 17 and 32 kcal/mol, respectively. The experimental value is 17.7 kcal/mol, in accord with the first mechanism (172). The structures and energies of seven types of cyclophane have been calculated (172). 

Wurster in 1879 had already prepared crystalline salts containing radical cation 23 (equation 12). Subsequently, radical cations of many different structural types have been found, especially by E. Weitz and S. Hunig, and recently these include a cyclophane structure 24 containing two radical cations (Figure 3). Leonor Michaelis made extensive studies of oxidations in biological systems, " and reported in 1931 the formation of the radical cation species 25, which he designated as a semiquinone. Michaelis also studied the oxidation of quinones, and demonstrated the formation of semiquinone radical anions such as 26 (equation 13). Dimroth established quantitative linear free energy correlations of the effects of oxidants on the rates of formation of these species. ... 

This type of cyclophanes (e.g., 62-65) were shown to be able to discriminate organic guests in aqueous solutions by recognition of both steric structure and charge. 

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