1 Department of Bioscience - Microbiology, Department of Bioscience, Science and Technology, Aarhus University2 Humboldt University of Berlin3 Department of Bioscience - Center for Geomicrobiology, Department of Bioscience, Science and Technology, Aarhus University4 Department of Bioscience - Center for Geomicrobiology, Department of Bioscience, Science and Technology, Aarhus University
A series of o-alkylphenyl alkyl ketones 1 were synthesized by different methods. The presence of a leaving group X adjacent to the carbonyl group is the special peculiarity of these ketones. Upon irradiation the keto carbonyl group of these compounds undergoes an n−π* excitation followed by a 1,5-hydrogen migration from the o-alkyl substituent to the carbonyl oxygen atom. The thus formed 1,4-diradicals are subject to a very rapid elimination of acid HX, giving 1,5-diradicals. We called this process spin center shift. After intersystem crossing these diradicals cyclize to 1-indanones 20 in good yields. Depending on the solvent and on substituents, o-alkoxyalkyl ketones 22 or benzo[c]furanes 21 are obtained as byproducts. The mechanism of the cyclization was elucidated by quantum chemical calculations and kinetic measurements.
Journal of Organic Chemistry, 2004, Vol 69, Issue 22, p. 7582-7591