Open Chain Cyclophanes

The phenylene rings of 1,8-diphenylnaphthalene (31) are arranged in a face-to-face manner60,61. Accordingly, a relatively low 5-value (6.85 ppm ) is found for the corresponding protons61.  

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Examples of the fruitful Portuguese-Spanish collaboration between Pina at Lisbon and Garcia-Espana at Valencia are the cyclophane compounds 55 and 56 [115] along with analogous open chain compounds where fluorescence is... 

The synthesis of the cyclophane 22 from the dibromide 19 and the bis (phenol) 20 was carried out in various ways [9i] on the one hand, stepwise via the open-chained intermediate 21 on the other hand, in a one-step cyclization of 19 and 20 ... 

The chemistry of cyclophanes, the first representative of which, [2.2]meta-cyclophane was prepared by Pellegrin [1] as early as 1899, was first systematically studied in the 1950s, mainly by the innovative work of Cram [2]. Through specific syntheses, he prepared new members and recognized characteristic differences with regard to open chained benzene derivatives. 

Arene complexes with mint metals are rather rare. The arene metal bond is weaker compared to the other transition metals and hapticity is lower. For this reason the stronger rr-donor properties of the cyclophanes compared to open chained arenes [109c] make the preparation in benzene solution possible. The cyclophane is simply heated with silver-I (Fig. 29a) [109a] or copper-I (Fig. 29b) [109b] and yields the respective complex formed in almost quantitative yield. It is noteworthy that the silver ion in 128 shows no interaction with the benzene ring at all the naphthalene unit acts as 7t-donor only [109a]. 

This is due to stabilization of the excited state in the cyclophane ligand compared to the open chain analog. The electron withdrawing effect of a second Cr(CO)3-group leads to a further increase in stability of the excited state as is seen in the complexes 35b and 36b this effect decreases when the distance of the Cr(CO)3-groups is increased (Fig. 38) [29, 40]. 

NMR spectra of cyclophanes are exceptional with respect to open chained benzene analogs (Fig. 39). 

Fig. 39. C-NMR (in brackets) and H-NMR data of [2.2]cyclophanes in comparison to an open chained analog [142]...

With these features in mind, we envisioned a new family of macrocyclic ligands for olefin polymerization catalysis (Fig. 9) [131, 132], We utilized macrocycles as the ligand framework and installed the catalytic metal center in the core of the macrocycles. Appropriate intra-annular binding sites are introduced into cyclophane framework that not only match the coordination geometry of a chosen metal but also provide the appropriate electronic donation to metal center. The cyclophane framework would provide a microenvironment to shield the catalytic center from all angles, but leaving two cis coordination sites open in the front one for monomer coordination and the other for the growing polymer chain. This could potentially protect the catalytic center and prevent it from decomposition or vulnerable side reactions. 

Peraza-cyclophanes have been prepared by first condensing the dialdehyde with a 1,8-naphthalenediamine to form two 1,3-diazacyclohexane units as shown below. The small diaza rings open on reduction to form a long-chain molecule with primary amines on each end. This material can be cyclized with another molecule of the dialdehyde (Yamamoto and Maruoka, 1981). 

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