A new photochromic 8pi-system based on an azaheptatriene-tetrahydroazepinoisoquinoline electrocyclization.
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.
Tan
Y
Y
FB 11.2 Organische Chemie, Universität des Saarlandes, D-66041 Saarbrücken, Germany.
Hartmann
T
T
Huch
V
V
Dürr
H
H
Valat
P
P
Wintgens
V
V
Kossanyi
J
J