Hexasulfanyl analogues of cyclotriveratrylene

The synthesis of four 3,4-di(alkylsulfanyl)benzyl alcohol derivatives is described, in five steps from methyl 3,4-di(hydroxy)benzoate via a Newman–Kwart rearrangement. Incubation of these derivatives in formic acid affords 2,3,7,8,12,13-hexakis(alkylsulfanyl)-10,15-dihydro-5H-tribenzo[a,d,g]cyclononene products, which are hexa-sulfanyl analogues of the well-known supramolecular cavitand host, cyclotriveratrylene (CTV). The yield of this cyclization depends strongly on the alkylsulfanyl substituents present, in the order SMe > SEt ≈ SiPr ? SBn. A crystal structure determination of one of the cyclotrimers shows a mode of self-association that is commonly exhibited by CTV itself.     

Synthesis and characterization of a biphenyl-linked hemicryptophane and an endohedral cobalt(II) complex

Hemicryptophanes are covalent molecular cages, constructed from a cyclotriveratrylene-based host unit and a functional unit linked by covalent spacers, which have been designed to accommodate endohedral functionalities in the cavity. In this study, the synthesis and characterization of the rigid, biphenyl-linked hemicryptophane 1 were investigated by NMR, ESI-MS, and X-ray crystallography. The structure of the inclusion complex, in which a dichloromethane molecule was constructed encapsulated within 1, was characterized by X-ray crystallography. An endohedral, cobalt(II) hemicryptophane complex 2 was also synthesized and characterized ESI-MS and X-ray crystallography. The X-ray crystal structure of 2 showed that the biphenyl-linked hemicryptophane had three components—a molecule each of chloroform and acetonitrile, and a cobalt(II) ion—within its cavity.     

Functionalization of Polyethyleneimine with Hollow Cyclotriveratrylene and Its Subsequent Supramolecular Interaction with Doxorubicin

In this paper, a modified Cyclotriveratrylene was synthesized and linked to a branched Polyethylenimine, and this unique polymeric material was subsequently examined as a potential supramolecular carrier for Doxorubicin. Spectroscopic analysis in different solvents had shown that Doxorubicin was coordinated within the hollow-shaped unit of the armed Cyclotriveratrylene, and the nature of the host–guest complex revealed intrinsic Van der Waals interactions and hydrogen bonding between the host and guest. The strongest interaction was detected in water because of the hydrophobic effect shared between the aromatic groups of the Doxorubicin and Cyclotriveratrylene unit. Density functional theory calculations had also confirmed that in the most stable coordination of Doxorubicin with the cross-linked polymer, the aromatic rings of the Doxorubicin were localized toward the Cyclotriveratrylene core, while its aliphatic chains aligned closer with amino groups, thus forming a compact supramolecular assembly that may confer a shielding effect on Doxorubicin. These observations had emphasized the importance of supramolecular considerations when designing a novel drug delivery platform.     

A facile synthesis of cyclotriveratrylene

Cyclotriveratrylene (CTV) can be readily synthesized by chloromethylation or bromomethylation of dimethoxybenzene with halomethyloctyl ether in the presence of SnCl₄. The reaction provides the trimer exclusively and in high yield. Recrystallizations from benzene or CHCl₃ yielded the solvent inclusion complexes and did not remove other inclusion impurities. Flash chromatography on silica yielded the pure CTV.¹³C NMR shows only five signals and no impurities.     

Supramolecular Complexation Behavior of Novel Cyclotriveratrylene Derivatives with Benzoate Pendants with C60

Four novel cyclotriveratrylene (CTV) derivatives with three benzoate pendants bearing different aliphatic chains have been prepared in good yields, starting from CTV. The complexation behavior of these CTV derivatives towards C₆₀ in arene solvents has been measured by UV‐visible spectroscopy and high complexation constants are obtained. It is observed that the complexation is promoted pronouncedly by introducing methyl ester groups to the aromatic pendants, while this promoting effect is reduced when the methyl groups are replaced by longer alkyl groups.     

Isolation of the saddle and crown conformers of cyclotriveratrylene (CTV) oxime

The oxime of cyclotriveratrylene (CTV) has been prepared and the individual crown and saddle conformers were isolated and characterized. The equilibrium constant was measured in CDCl₃ and in DMSO-d₆ and was shown to favor the crown conformer by an order of magnitude in DMSO-d₆, relative to an approximately equal mixture at equilibrium in CDCl₃. The time course for interconversion of the saddle to the crown was measured by ¹H NMR and the t_1/2 of the saddle was determined to be 2.45 h in CDCl₃ at 25 °C, and 3.71 h in DMSO-d₆.     

Arranging coordination sites around cyclotriveratrylene

This article describes the attachement of coordination sites around a rigid matrix: cyclotriveratrylene (CTV). The synthetic approaches leading to these new ligands possessing pyridines and bipyridines as coordinating sites are discussed and full synthetic details are given. One expanded CTV derivative bearing three 3-pyridyl groups has been characterized by X-ray crystallography and the structure shows that the conformation adopted by the CTV matrix is appropriate for the coordination of transition metals, and inclusion of a range of molecules in the hydrophobic pocket.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Synthesis and Structural Studies of Cyclotriveratrylene Derivatives

Cyclotriveratrylene (CTV) derived host molecules with ethyl, propyl, allyl or propargyl functional groups have been synthesised using standard or solventless reaction methodologies. The known structural and clathrate chemistry of cyclotriveratrylene (CTV) and these analogues has been extended. Crystal structures of the hexa(ethyl), tri(ethyl), tri(propargyl) analogues have been determined, and show either intra-cavity host-guest binding or self-stacking motifs. Two new clathrates of CTV have also been structurally characterised, namely CTV.(DMSO)₂.(H₂O)₂ with intra-cavity complexation of DMSO, and CTV.(EtOH)_0.25 which has a γ-phase CTV structure.     

Inclusion Compounds of Cyclotriveratrylene (2,3,7,8,12,13-hexamethoxy-5,10-dihydro-15H-tribenzo[a,d,g]cyclononene) with Chlorinated Guests

Inclusion compounds were formed between the host cyclotriveratrylene, H, (2,3,7,8,12,13-hexamethoxy-5,10-dihydro-15H-tribenzo[a,d,g]cyclononene) and the guests carbon tetrachloride, 1,1,1-trichloroethane, 1,1,1-trichloropropane and 1,1,2-trichloroethane. 1 (H·CCl₄) has guest molecules in channels alternating with channels of host molecules. 2 (H·C₂H₃Cl₃·C₃H₅Cl₃) and 3 (H·2C₂H₃Cl₃) exhibit a slightly different packing arrangement with one guest molecule in the host cavity and the rest of the guest molecules in channels. The stability and reactivity of these inclusion compounds were investigated.