Photochemical Synthesis of Azepinoindoles and Azocinoindoles from N-Chloroacetylindolylethylamines, and a Mechanistic Study based on the Correlation between Quantum Yields and Calculated Frontier Electron Densities of Indole Radicals

摘要: On irradiation in 50% aqueous ethanol, the N-chloroacetyl derivatives of seven isomeric indolylethylamines gave corresponding azocinoindole through photocyclization at ortho and peri positions. Quantum yields for product formation with 2537 A light showed relative reactivity each position indole ring to be order 3>6, 4>7, 2>5>1. In identify reactive intermediary species establish mechanism photocyclizations, frontier electron densities several were calculated by CNDO/2 INDO. The quantum from 1-substituted correlated fairly well (correlation coefficient r=0.82) singly occupied molecular orbitals (SOMO) (ED) 1-methylindole radical cation, but there was a better correlation (r=0.90) between 1-unsubstituted compounds SOMO-ED indole-1-radical. These results show that N-chloroacetylindolylethylamines involves both cations indole-1-radicals as species.