Abstract
Prompted by the selectivity observed during the oxidation of 1‐methylcyclohexene included within a water‐soluble capsule by singlet oxygen, we conducted oxidation of a number of 1‐alkylcyclohexene derivatives. Of the three possible allylic hydrogens that could be ed by the attacking singlet oxygen, there was a preference for one of them but not to the extent that is observed with 1‐methylcyclohexene. The observed high selectivity with 1‐methylcyclohexene and moderate to low selectivity observed with longer n‐alkyl substituted cyclohexenes is rationalized on the basis of the available free space around the three allylic hydrogens. A comparison of the behavior of eight 1‐alkylcyclohexenes reveals that the behavior of confined reactant molecules cannot be extended based on a single model compound. The results presented demonstrate that the chemistry within supramolecular assemblies could be unique for each molecule just like in an enzyme.
Caught in a trap: Studies on the singlet‐oxygen‐mediated oxidation of a series of olefins encapsulated within a confined cage has revealed that the selectivity is specific and depends on the alkyl chain length. For example, while 1‐methylcyclohexene gave unprecedented selectivity, the 1‐ethylcyclohexene gave moderate selectivity and longer alkyl substitution gave poor selectivity although the alkyl chain is not the reactive center. The results suggest that the reactivity of molecules stationed in confined spaces is controlled by structural rather than electronic features.
