Investigating the arenyl-diene double [3 + 2] photocycloaddition reaction.

The double [3 + 2] photocycloaddition reaction involving arenyl-dienes has been used to assemble seven separate [5.5.5.5] fenestrane structures that include ether and aza variants. The primary photolysis step was a meta photocycloaddition reaction, while a secondary photocycloaddition step formed the fenestrane structure. Investigations involving the insertion of an additional methylene group into the basic arenyl-diene skeleton failed to afford the desired [5.5.5.6] fenestrane structure. The presence of an oxime moiety in the aromatic photosubstrate allowed the primary photolysis step to take place; however, an attempted secondary photocycloaddition reaction involving the oxime did not provide the intended polyheterocyclic fenestrane. An alternative strategy to form various "criss-cross" double meta photocycloadducts was investigated and led to the discovery of a Paterno-Büchi cycloaddition reaction between acetone and an angular meta photocycloadduct. Other novel thermally and photochemically mediated skeletal rearrangement reactions were also recorded.