Electronic-state switching strategy in the photochemical synthesis of indanones from o-methyl phenacyl epoxides

An electronic excited-state switching strategy has been utilized to control the selectivity of a key photochemical step in the total synthesis of indanorine. The excited-state character of 4,5-dimethoxy-2-methylphenacyl epoxide was changed from an unfavorable (3)π,π* state to a productive (3)n,π* state by a temporary structural modification, resulting in a relatively efficient and high-yielding formation of an indanone derivative. The corresponding structural modification was selected on the basis of quantum chemical calculations prior to the synthesis.