A novel cyclophane. Host-guest complexation and selective inclusion of aromatic guests from nonaqueous solution

Abstract

Asymmetric Reduction of Benzoylformic Ester to Methyl Mandelate ( S )or (R)-18. GeneralProcedure for 20-50-mg Scale. An ampule (2 mL) containing magnesium perchlorate (Mg(CIO,),-l .5 H 2 0 , 1 .O equiv) sealed with a small rubber septum was evacuated and flushed with argon several times. Methyl benzoylformate (1 .O equiv) was injected via syringe, followed by a solution of the 1,4-dihydropyridine (1.0 equiv) in freshly distilled acetonitrile (1 mL). The ampule was kept in the dark and the reduction allowed to proceed for 5-10 days monitored by TLC. After this period, water (100-200 pL) was added, and the reaction mixture was concentrated in vacuo. The residue was triturated with boiling chloroform (2-3 mL) and the relative yield of methyl mandelate 18, as a chloroform solution, was determined by using capillary GC." The chloroform solution was concentrated to about 0.1 mL, and the alcohol 18 was isolated via preparative TLC using 20% ethyl acetatehexanes as the eluent. Extraction of the silica gel bands, with ethyl acetate, gave methyl mandelate after filtration through a millipore filter, and concentration gave the crystalline alcohol 18. After dissolving this material in 1.0 mL of methanol, the specific rotation of the sample was measured, followed by determination of the accurate concentration of 18 in the alcohol using HPLC calibration.'* Pyridinium Salt 20. Isolation of the pyridinium salt 20 was achieved during the preparative TLC by extraction of the base-line silica gel layers with ethyl acetate (5 mL). Filtration and concentration gave the orange salt 20 (40-50% recovery): 'H N M R (CD,CN) 6 9.08 (br s, 1 H, 6-H), 8.79 (br s, 1 H, 2-H), 7.60-7.40 (m, 5 H, C6H5), 5.77 (s, 2 H, CH2C6Hj). 4.82 (d, J = 5.2 Hz, 2 H, CHIOH), 4.68 (br s, OH), 4.42 Abstract:A novel c y c l o p h a n e , 2,2,20,20-tetramethyI-1 1,29-dinitro-7,15,25,33-tetraoxaheptacyclo-[32.2.2.23~6.216~19.221~24.19~13.127~3'] hexatetraconta-3,5,9(44),10,~2,16,18,21,23,27(39),28,30,34,36,37,40,42,45-octadecaene ( l ) , was synthesized by the reaction of 3,5-bis(bromomethyl)nitrobenzene (2) with bisphenol A (3). Both stepwise 2:2 cyclization of 2 and 3 via U-shaped precursor 4 and direct 2:2 cyclization of 2 and 3 were performed under several reaction conditions.With the coexistence of benzene in the reaction solvent, relatively high yield of 1 was achieved even without operation under high dilution conditions. This can be explained in term of a "template" effect of benzene in the cyclization step. The cyclophane

Ruthenophanes: Evaluating Cation−π Interactions in [Ru(η6-C16H12R4)(NH3)3]2+/3+ Complexes. A Computational Insight

“…15 Cyclophanes have also been employed as selective catalysts, as auxiliaries in asymmetric synthesis, 16 as catalysts that simulate enzymatic functions, 17 in supramolecular chemistry, 18 in optoelectronic devices, 19,20 as precursors of nonlinear optical materials, 21 and in the preparation of artificial receptors. 22,23 The occurrence of transannular interactions 9,10 in cyclophanes has been detected not only by photoelectrons spectroscopy and by electronic spin resonance (ESR) 24,25 but also by other spectroscopic analyses such UV−vis and NMR. 26 These transannular interactions between the aromatic decks give a unique π-electron system, which is present not only in double-deck systems but also in multilayered [2 n ]cyclophanes.…”

“…The intrinsic structural features of [2 n ]cyclophanes make them attractive probes to investigate and to comprehend the interplay between strain versus aromaticity, the role of transannular effects ( through-bond and through-space interactions), − the effects of substituents in transannular π–π interactions, , chemical shifts in aromatic systems, intramolecular charge transfer processes, − and transannular reactions . Cyclophanes have also been employed as selective catalysts, as auxiliaries in asymmetric synthesis, as catalysts that simulate enzymatic functions, in supramolecular chemistry, in optoelectronic devices, , as precursors of nonlinear optical materials, and in the preparation of artificial receptors. , The occurrence of transannular interactions , in cyclophanes has been detected not only by photoelectrons spectroscopy and by electronic spin resonance (ESR) , but also by other spectroscopic analyses such UV–vis and NMR . These transannular interactions between the aromatic decks give a unique π-electron system, which is present not only in double-deck systems but also in multilayered [2 n ]cyclophanes …”

A comparison of the crystal packing in benzene with the geometry seen in crystalline cyclophane-benzene complexes: guidelines for rational receptor design

“…Compared w ith the situation of the intra-cavity benzene in the crystal structure of 2 (figure 2), a reduced affinity of benzene tow ard host 3 is to be expected. Accordingly, whereas cyclophane 1 (as quaternary ammonium derivative) binds benzene in aqueous solution (Diederich et al 1985), no evidence for 1:1 host-guest com plexation by 3 in solution has been reported (Saigo et al 1985(Saigo et al , 1986. Nevertheless, packing motifs from crystalline benzene can still be detected in the structural organization of this complex.…”

“…In the same year, Saigo et al (1985Saigo et al ( , 1986 reported th a t cyclophane 3 forms a crystalline 1: 1 complex (4) w ith benzene, and the X -ray crystal structure analysis showed th a t the guest is located between two host molecules. Later, Brown et al (1989) found th a t the hexaoxacyclophane 5 forms a 1:1 molecular complex (6) in which benzene is encapsulated in the macrocyclic cavity.…”