Cyclophane derivatives

In 1955, cyclophane derivatives of type (261) (with n = 3 or 4) were described (Stetter Roos, 1955). After recrystallization from benzene or dioxan, these species crystallized as the 1 1 adducts of these solvents. Once such adducts are formed, it is difficult to remove the solvent and it was concluded that the solvent molecules are housed inside the cavities of the respective guests. In accord with this, the smaller ring system (261 ... 

Cyclic thioethers involving rigid linkages are also known. Examples include a range of derivatives of [14]aneS4 incorporating 1,2-benzene and/or 1,2-cyclohex-ane units 79 TTOB, TTMB 80 tetrathia and hexathia cyclophane derivatives.81 84... 

The absolute configuration of more than 20 optically active [2.2]para-cyclophane derivatives has been established in this way. 

Figure 11.11 Cyclophane derivatives and anionic gold NPs generate nanocomposite assemblies on an electrode surface. Adapted from Ref. 45 with permission.

Boekelheide and his collaborators [407] have described a two-step sequence for transforming sulfide linkages to carbon-carbon double bonds — Stevens rearrangement of sulfur ylides and Hofmann elimination — which they found particularly useful for the synthesis of cyclophane derivatives, such as the [2.2]metaparacyclophane-l,9-diene shown. The Ramberg-Backlund rearrangement (see Section 4.3.2) was unsatisfactory for such highly strained molecules. 

Kotha, S., Mandal, K., Suzuki-Miyaura cross-coupling and ring-closing metathesis A strategic combination for the synthesis of cyclophane derivatives. Eur. J. Org. Chem. 2006, 5387-5393. 

Chen, G. Y., Lean, J. T., Alcala, M., Mallouk, T. E., Modular synthesis of -acceptor cyclophanes derived from... 

Fig. 1 Naturally occurring cyclophane derivatives belonging to the Turriane family...

Derivatives involving two TTF units connected by a saturated spacer exhibit interesting features as well. Thus the BEDT-TTF analog 41, which contains two TTF moieties [71] shows only two oxidation waves at similar potentials to that of BEDT-TTF. Three redox waves have been detected for compounds 42 [72], 43 [73] (n = 1, 2) and 44 [74] (n = 3), whereas they collapse into two waves for a longer chain (n > 2 for 43, n > 3 for 44). Three reversible oxidation waves have been observed for a cyclophane derivative containing two TTF units [75]. Some representative data are collected in Table 9. 

A Merck group reported an interesting kinetic resolution of a racemic di-bromocyclophane via Pd-catalyzed amination [91]. While BINAP was a poor ligand for the reaction in terms of selectivity, the C2-symmetric cyclophane-derived PHANEPHOS (17) proved to be optimal. Reaction of the cyclophane derivative with benzylamine afforded the unreacted dibromide in 45% ee after 37% conversion, corresponding to a selectivity factor of 12, Eq. (78). 

The first total synthesis of three naturally occurring cyclophane derivatives belonging to the turriane family of natural products was also described by A. Furstner et al These natural products have a sterically hindered biaryl moiety and saturated as well as unsaturated macrocyclic tethers. Stereoselective entry to this class of compounds is possible using RCAM followed by Lindlar reduction of the resulting cycloalkynes. 

More useful mechanistic information is obtained from intramolecular electron-transfer reactions if the kinetics for the electron-transfer step can be isolated from the effects of diffusion. The main stimulus for making such studies is the urge to design systems that mimic some of the essential features of the photosynthetic reaction centre complex and much attention has focussed on the study of porphyrin-based photoactive dyads. Thus, a series of N-alkylporphyrins linked to a quinolinium cation has been synthesized and found to display a rich variety of photoreactions. The singlet excited state of the quinolinium cation operates in both intramolecular energy- and electron-transfer reactions while the excited singlet state of the porphyrin transfers an electron to the appended quinolinium cation. Several new porphyrin-quinone dyads have been studied,including cyclophane-derived systems where the reactants are held in a face-to-face orienta-... 

A further example of a tailor-made host compound is cryptophane (162) By use of this cyclophane derived from the triveratrylene skeleton and having a large cavity inside the molecule, the differentiation of bromochlorofluoromethane (136) was successfully carried out on an analytical scale. Bromochlorofluoromethane has also been optically enriched through complexation with brucine... 

Calixarenes are oligomeric cyclophanes derived from the condensation of phenols with formaldehyde. They became popular in the late seventies and have played a very important role in Supramolecular Chemistry ever since, as witnessed by numerous books and review articles on the subject. Calixarenes are important bnilding blocks for the preparation of a large variety of supramolecular complexes and materials, thanks to their ability to act as hosts, and the possibility of introdncing a large nnmber of functions at either rim by means of selective derivatization. 

Benniston. A.C. Harriman. A. Philp. D. Stoddart, J.F. Charge recombination in cyclophane-derived intimate radical ion pairs. J. Am. Chem. Soc. 1993. 115. 5298-5299. 

Suzuki. T. Miyake, M. Preparation of Cyclophane Derivative for Treatment of Malignant Tumor. JP Patent 2003073379. Chem. Abstr. 2003, 38. 221609. 

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