title: A new photochromic 8pi-system based on an azaheptatriene-tetrahydroazepinoisoquinoline electrocyclization.
abstract: A new photochromic family of tetrahydroazepinoisoquinolines (THAI) 4a-i has been prepared. It undergoes light-induced ring opening from spiro compounds 4 to betaines 3 that decolorize in a very fast cyclizing reaction. Depending on substitution of the precursors 1 and 6, the photochromic styryltetrahydroindolizines (THI) 5k-q are formed in a periselective way. The conformation and configuration of the new photochromic THAI 4 and THI 5 were investigated by NMR and the structure of both compounds was proven by X-ray analysis. The photochromic properties were studied by laser flash photolysis, which afforded the lifetime of the colored form 3 and 3' in the micro- or nanosecond range.
authors: FB 11.2 Organische Chemie, Universität des Saarlandes, D-66041 Saarbrücken, Germany.
authors: Y
authors: Y
authors: Tan
authors: T
authors: T
authors: Hartmann
authors: V
authors: V
authors: Huch
authors: H
authors: H
authors: Dürr
authors: P
authors: P
authors: Valat
authors: V
authors: V
authors: Wintgens
authors: J
authors: J
authors: Kossanyi