Reaction prototypes, cage 4 + 4 -Reactions

In a second example the discrete time-reversible propagation scheme for mixed quantum-classical dynamics is applied to simulate the photoexcitation process of I2 immersed in a solid Ar matrix initiated by a femtosecond laser puls. This system serves as a prototypical model in experiment and theory for the understanding of photoinduced condensed phase chemical reactions and the accompanied phenomena like the cage effect and vibrational energy relaxation. It turns out that the energy transfer between the quantum manifolds as well as the transfer from the quantum system to the classical one (and back) can be very well described within the mixed mode frame outlined above. 

Being the prototype of a reaction involving in-cage recombination versus diffusion of radicals, the PFR constitutes an appropriate probe to disclose how the nature of the experienced microenvironment modulates photochemical reactivity and selectivity. Among the investigated hosts, special attention is devoted to cyclodextrins, micelles, zeolites, proteins, and polymeric matrixes. 

In this chapter, prototypes of the photochemical reactions useful for the synthesis of cage compounds are outhned first, and then photochemical approaches towards the synthesis of [n]prismanes as representative cage compounds are reviewed. 

Prototypes of the Photochemical Reactions for the Synthesis of Cage Compounds... 

Prototypes of the photochemical reactions for the synthesis of cage compounds are classified as shown in Table 22.1. The most predominant examples are [2 + 2]-reactions of Diels-Alder adducts with an endo-configuration. Intramolecular photochemical [2 + 2]-, (6 +2 ]- and [6 -I- 6]-reactions in the rigid polycycHc framework have been increasingly employed for the synthesis of polycyclic cage compounds. Other photochemical reactions, such as [4 -t 4]-cycloaddition and related processes, are also important. According to this arrangement, prototypes of the photocycloadditions and their important applications are described. 

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