Engineering acyclic alkyl aryl ketones for enantioselective Norrish/Yang type II photochemistry in the crystalline state

While most alkyl aryl ketones fail to undergo the Norrish/Yang type II photoreaction in the solid state because they crystallize in conformations unfavorable for gamma-hydrogen atom abstraction, it was found with the aid of molecular mechanics that such is not the case for the 2-ethyl-1-arylbutan-1-one system; subsequent application of the solid state ionic chiral auxiliary method of asymmetric synthesis to derivatives of this ketone afforded the corresponding Yang cyclobutanol in enantiomeric excesses as high as 92% at 91% conversion.