Cyclotriveratrylenes and cryptophanes
About: This article is published in Tetrahedron.The article was published on 1987-01-01. It has received 345 citations till now. The article focuses on the topics: Cryptophane & Cyclophane.
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TL;DR: This tutorial review focuses on the use of dynamic imine bonds in the construction of compounds and products formed with and without the aid of additional templates.
Abstract: Formation of an imine—from an amine and an aldehyde—is a reversible reaction which operates under thermodynamic control such that the formation of kinetically competitive intermediates are, in the fullness of time, replaced by the thermodynamically most stable product(s). For this fundamental reason, the imine bond has emerged as an extraordinarily diverse and useful one in the hands of synthetic chemists. Imine bond formation is one of a handful of reactions which define a discipline known as dynamic covalent chemistry (DCC), which is now employed widely in the construction of exotic molecules and extended structures on account of the inherent ‘proof-reading’ and ‘error-checking’ associated with these reversible reactions. While both supramolecular chemistry and DCC operate under the regime of reversibility, DCC has the added advantage of constructing robust molecules on account of the formation of covalent bonds rather than fragile supermolecules resulting from noncovalent bonding interactions. On the other hand, these products tend to require more time to form—sometimes days or even months—but their formation can often be catalysed. In this manner, highly symmetrical molecules and extended structures can be prepared from relatively simple precursors. When DCC is utilised in conjunction with template-directed protocols—which rely on the use of noncovalent bonding interactions between molecular building blocks in order to preorganise them into certain relative geometries as a prelude to the formation of covalent bonds under equilibrium control—an additional level of control of structure and topology arises which offers a disarmingly simple way of constructing mechanically-interlocked molecules, such as rotaxanes, catenanes, Borromean rings, and Solomon knots. This tutorial review focuses on the use of dynamic imine bonds in the construction of compounds and products formed with and without the aid of additional templates. While synthesis under thermodynamic control is giving the field of chemical topology a new lease of life, it is also providing access to an endless array of new materials that are, in many circumstances, simply not accessible using more traditional synthetic methodologies where kinetic control rules the roost. One of the most endearing qualities of chemistry is its ability to reinvent itself in order to create its own object, as Berthelot first pointed out a century and a half ago.
859 citations
736 citations
TL;DR: The unique behavior that emerges from molecules that are simultaneously encapsulated is described and includes new forms of stereochemistry, isomerism, and asymmetry inside capsules.
Abstract: Reversible encapsulation creates spaces where molecules are temporarily isolated from others in solution. Molecules are held within the space of the capsule for lifetimes ranging from milliseconds to hours, and conventional NMR spectroscopy can be used to report on the chemical and magnetic environment as well as the arrangement of the molecules in the encapsulation complex. The complexes self-assemble when, and only when, the spaces inside the capsules are appropriately filled. The weak intermolecular forces that hold these self-assemblies together allow equilibration of the encapsulation complexes at ambient temperatures and pressures in the liquid phase. When two or more molecules are simultaneously encapsulated, intermolecular phenomena are revealed in solution that cannot be observed by other methods. We describe here the unique behavior that emerges from molecules that are simultaneously encapsulated and includes new forms of stereochemistry, isomerism, and asymmetry inside capsules.
450 citations
TL;DR: This Perspective discusses recent developments with discrete organic molecules that are porous in the solid state and focuses on the possible advantages of organic molecules over inorganic or hybrid systems in terms of molecular solubility, choice of components and functionalities, and structural mobility and responsiveness in non-covalent extended solids.
Abstract: Most synthetic materials that show molecular-scale porosity consist of one-, two- or three-dimensional networks. Porous metal-organic frameworks in particular have attracted a lot of recent attention. By contrast, discrete molecules tend to pack efficiently in the solid state, leaving as little empty space as possible, which leads to non-porous materials. This Perspective discusses recent developments with discrete organic molecules that are porous in the solid state. Such molecules, which may be either crystalline or amorphous, can be categorized as either intrinsically porous (containing permanent covalent cavities) or extrinsically porous (inefficiently packed). We focus on the possible advantages of organic molecules over inorganic or hybrid systems in terms of molecular solubility, choice of components and functionalities, and structural mobility and responsiveness in non-covalent extended solids. We also highlight the potential for 'undiscovered' porous systems among the large number of cage-like organic molecules that are already known.
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426 citations
TL;DR: Organic hosts are now being designed and synthesized which contain enforced cavities large enough to complex and even surround simple inorganic or organic guest compounds.
Abstract: Organic hosts are now being designed and synthesized which contain enforced cavities large enough to complex and even surround simple inorganic or organic guest compounds.
405 citations
TL;DR: In this paper, it is shown that to produce optical rotation in a chromophore, a potential function must have the symmetry properties of a pseudoscalar in the symmetry group of the unperturbed chromophores.
Abstract: It is shown that to produce optical rotation in a chromophore, a potential function must have the symmetry properties of a pseudoscalar in the symmetry group of the unperturbed chromophore It is thus possible to establish regional rules of optical rotation without recourse to particular models and assumptions of the electronic states of the chromophore Formulas and geometric representations of the resulting regional rules are given for a number of symmetries which are encountered in molecular problems The results are not applicable to coupled oscillator models of optical rotation
354 citations
TL;DR: The relationship between the CD spectra of the chiral biaryls and their stereochemical configuration, as a function of the dihedral angle between the molecular planes of the aromatic moieties, has been investigated in this article.
200 citations
174 citations