Reaction cavity cage effects

The cage effects measured in various media are compiled in Table 2. Results clearly show that all of the organized media listed in the table have a cage effect larger than is observed in benzene ( 0%). Also note that the magnitudes of the cage effect and the yields of the rearrangement product depend on the medium (probably a reflection of the differences in the characteristics of the reaction cavity in various media). 

The importance of the size of the enclosure (reaction cavity) on a reaction course has been a subject of investigation in several laboratories. On the basis of the proposed mechanistic scheme for DBK fragmentation and on the basis of the effective reaction cavity model presented in Section III, the following predictions can be made (a) a relationship will exist between the cage effect and the reaction cavity size (b) the cage effects observed for singlet and triplet benzyl radical pairs will be different (assuming very similar diffusion rates)... 

In all the reactions described above, CyDs promote para-selectivity. In some reactions, however, CyDs catalyze the formation of ortho-products. When anisole and pentyl chloroacetate in the presence of a-CyD (3 mM), ortho-alkylated anisole is efficiently and selectively formed (80% selectivity) [18a]. The selective reactions are ascribed to a cage effect and geometric control to the CyD cavity. 

The synthesis of nanoparticles inside MOFs is another, still more special example of reactions inside the framework. Nanoparticles trapped inside MOF cavities, with a high number of reactive surface atoms, are indeed reactive species as well. Their synthesis inside the porous hosts, starting from molecular precursors, anticipates the caging effect of the framework. To prevent the clusters from growing to larger, bulk agglomerates, the space confinement of the framework pores is utilized naturally. 

A self-assembled coordination cage and micelles were found to accelerate Diels-Alder reactions in an aqueous media. The catalysis of Diels-Alder reactions via noncovalent binding by synthetic, protein, and nucleic acid hosts has been surveyed and compared to explore the origin of the noncovalent catalysis. These catalysts consist of binding cavities that form complexes containing both the diene with the dienophile and the reaction occurring in the cavity. The binding requires no formation of covalent bonds and is driven principally by the hydrophobic (or solvophobic) effect. ... 

In the synthesis of many cryptands, a metal ion has been specifically employed as a template (often chosen to match the cavity size of the target cage) to boost the yield of the product. In other cases, a metal template effect is undoubtedly in operation through the use of an alkali metal reagent even though such a role had not always been anticipated when the synthetic procedure employed was chosen. However, it needs to be noted that apart from the above a number of other reaction types, employing a diverse range of precursors, have been employed for cryptand formation. ... 

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