Solid-state inclusion hosts

Fig. 5 Typical examples of (a-c) self-assembling inclusion hosts (d-f) interlocked and interwoven systems and (g-j) solid state inclusion hosts (a) tennis ball dimer (b) metallamacrocycle (c) ladder-structured metal array (d) catenane (e) rotaxane (f) helicate (g) network lattice host (exemplary host molecule) (h) coorclinatoclathrate host (exemplary hosts) (i) curved framework host molecule and (j) aukward-shape host molecule.

Toda and Akai49 reported that compound 48 reacted with the stable solid state inclusion compound of chiral host 46 and meso-ketone 47, providing alkene 49 in 57% ee. 

Host and guest are terms covering all kinds of intermolecular associations from the well-defined supermolecules to loosely packed solid state inclusion compounds. 

When greater selectivity is required in the solid-state reaction, host-guest chemistry techniques can be applied efficaciously. Reaction in the solid state of the guest compound as its inclusion complex crystal with a chiral host can give an optically active reaction product. Various host compounds have been designed by us to follow this simple principle. 

Table 1 An illustrative timeline charting the development of supramolecular chemistry from its roots in solid-state inclusion compounds, through the birth of macrocyclic host-guest chemistry in the 1960s to its modem incarnation in self-assembled materials and nanoscale chemistry.

Solid-state inclusion chemistry concerns the formation of host-guest compounds, their characterization by means of an extensive arsenal of analytical techniques, and their description. In most cases, guest molecules occupy lattice sites in crystals and it is therefore possible to obtain accurate crystallographic information regarding their locations within the guest-accessible spaces formed by the host framework. These spaces may consist of cavities or channels, and a number of computer programs are now able to map the surfaces that define the boundaries of the guest-accessible volume. Channels can be one-, two-, or three-dimensional (two- and three-dimensional channels... 

Clathrate A solid-state inclusion complex where the guest is held in a cavity, or channel in the crystal lattice of the host. A clathrate is destroyed when the crystal is dissolved. 

Truter, R. M., and Pedersen, C.J., Kryptate, Endeavour, Amsterdam, 1971, 142. Weber, E., Jozel, M. E, Puff, H., and Franken, S.. Solid-state inclusion compounds of new host macrocycles with unchanged organic molecules. Host synthesis, inclusion properties and X-ray crystal structure of an inclusion compound with 1-propanol,/. Org. Chem., 50, 3125, 1985. 

Walliman, P., Mattel, S., Seiler, P. Diederich, F. (1997) New cyclophanes as initiator cores for the construction of dendritic receptors Host-guest complexation in aqueous solutions and structures of solid-state inclusion compounds, Helv. Chim. Acta, 80, 2368-2390. 

Inclusion Complexes in the Solid State Cyclodextrin Hosts Zeolites 73-10... 

A regio- and stereoselective Beckmann rearrangement utilized diastereose-lective host guest interactions of the inclusion complexes 225 and 228 in a solid state reaction. Initially, a 1 1 mixture of the chiral host 223 and the racemic oximes 224 and 227, respectively, was treated with ultra sound in the solid state to induce the optical resolution. Then H2SO4 was added to start the Beckmann rearrangement, the corresponding c-caprolactams 226 and 229 were isolated in 68 % and 64 % yields and ee of about 80 % and 69 % (determined by HPLC analysis on chiracel OC) (Scheme 43) [46]. 

An enantioselective Michael addition reaction was also accomplished in an inclusion complex with a chiral host compound. Treatment of a 1 1 complex of 10c and 66b with 2-mercaptopyridine (137) in the solid state gave (+)-138 of 80% ee in 51% yield. By a similar method, 3-methyl-3-buten-2-one (139) gave (+)-140 of 49% ee in 76% yield [30]. 

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