Oxyfunctionalization of Alkenes by Dye-Sensitized Intrazeolite Photooxygenation

Abstract

This review focuses on the recent achievements towards the selective formation of allylic hydroperoxides by the reaction of singlet molecular oxygen ( 1 O 2) with alkenes adsorbed in the cavities of zeolite Na-Y. The product distribution by zeolite confinement is often dramatically different compared to the photooxygenation reaction in a homogeneous medium. Cation - π interactions and cation - singlet oxygen interactions, in the rate-limiting transition states, are most likely responsible for the changes in product selectivity within Na-Y. STRUCTURAL FEATURES OF FAUJASITES Zeolites are crystalline aluminosilicates whose primary structure is formed by SiO4 4- and AlO4 5- tetrahedra sharing the edges (1). Their tertiary structure forms strictly uniform channels and cavities of molecular dimensions that are repeated along the zeolite lattice. Due to the lower valence of the aluminum relative to silicon, the excess negative charge (one per Al atom) is balanced by alkali metal cations, mainly Na + . The cations are placed in the interior of cavities and can be easily exchanged. The cation-exchange process leads to new type of materials having interesting properties (2), and it is expected in the near future that the metal- supported zeolites will find significant applications in applied chemistry.