Synthesis and photoreaction of tricyclo[5.2.2.0
2,6]undecanes in the excited singlet (1S![](https://www.rsc.org/images/entities/char_200a.gif)
) state: a novel and stereospecific route to protoilludanoids
Abstract
A novel and general approach to the synthesis of functionalised protoilludane skeletons having fusedfour-, six- and five-membered rings is described. A photochemical sigmatropic 1,3-acyl shift in endo-tricyclo[5.2.2.02,6]undecanes having a β,γ-unsaturated carbonyl chromophore, and π4s + π2s cycloaddition of spiro[cyclohexa-2,4-diene-oxiran]-6-one are the key features of this approach. An efficient one-step synthesis of the epoxy ketone 11 by π4s + π2s cycloaddition of the in situ generated spiro[cyclohexa-2,4-diene-oxiran]one is reported. Further transformation of 11 to a variety of endo-tricyclo[5.2.2.0
2,6]undecanes (20, 25, 28, 30 and 31) and their photochemical behaviour upon singlet (1S
) excitation is described. Direct excitation of all the tricyclic chromophoric systems in benzene neatly furnished the protoilludanoids 32–36.