Photochemistry of 1-lsopropylcycloalkyl Aryl Ketones:Ring Size Effects,Medium Effects,and Asymmetric Induction

摘要

The n=0,1,and 2 ketones shown above undergo Yang photocyclization in solution,but only the n=1 analogues react this way in the solid state.Based on X-ray crystallography,these differences in reactivity are attributed to an unusually large distance for 1,4-hydroxybiradical cyclization in the solid state for the n=0 and 2 ring systems,which leads to predominant reverse hydrogen transfer(rht).Enantiomeric excesses of up to 99%can be achieved in the case of the n=1 system through the use of the solid-state ionic chiral auxiliary method of asymmetric synthesis.