Intramolecular cyclizations via photostimulated tethered free radical reaction towards α-tetralones and their analogues

Photostimulated tethered free radical reactions for the intramolecular cyclizations towards α-tetralones, N-containing α-tetralone analogues, 3,4,4a,10b-tetrahydro-2H-pyrano[3,2-c]chromen-5-ones and 2,3,4,4a,6,10b-hexahydropyrano[3,2-c]quinolin-5-one were investigated. Photolysis of the t-BuHgX/Dabco with 1-aryl-4-penten-1-ones produced α-tetralones via tert-butyl radical attacks on the terminal, followed by secondary radical attack to the aromatic ring, proton abstraction and electron transfer from the radical anion intermediate to t-BuHgX. At similar conditions, formation of N-containing α-tetralone analogues, 3,4,4a,10b-tetrahydro-2H-pyrano[3,2-c]chromen-5-ones and 2,3,4,4a,6,10b-hexahydropyrano[3,2-c]quinolin-5-one also occurs in reasonable yields.