Photochromic Heterocyclic Fulgides. Part 4.' The Thermal and Photochemical
Reactions of ( E )lsopropyl idene-[a-(2and -(3-t h ienyl)ethyl idene]succinic
Anhydrides and Related Compounds
The thermally-stable coloured form 5a, obtained by irradiation (A = 366 nm) of the title compound 4a, contains a rigid inflexible spiroadamantylidene group which results in a fiveto nine-fold increase in the quantum efficiency for bleaching compared t o the analogous compound 2 having methyl groups in the 7-position. The quantum efficiency for bleaching decreases with increasing wavelength of irradiation and increases with increasing temperature in a linear manner, and is solvent dependent.' r This study was carried out at the Chemistry Department, Weizmann Institute, Rehovoth, Israel, using a Cary spectrometer with a thermostatted variable-temperature cell, with irradiation at IE 366 nm in situ. We thank Professor E. Fischer for the use of his special facilities.
Scheme II (a, 3 ), 3.20 (m, 2 ), 5.70 (m, 1 H), and 7.63 (m, 4 H).Preparation of 1,3-Diazacyclonona-1,2-diene (I). In scrupulously dried equipment under nitrogen,(5.00 g, 0.0169 mol), potassium tert-butoxide (MSA Research, 2.37 g, 0.0211 mol), and freshly distilled (from P206) methylene chloride (225 mL) were refluxed for 1 h. After the mixture was filtered, solvent was removed, and the resulting yellow liquid was distilled. I (1.54 g, 73.3%) was obtained [bp 48 °C (0.85 mm)]: IR (neat) 3000-2850, 2100 (s) cm"1; NMR (CDC13) 5 3.30 (m, 4 ), 1.80 (s, 8 H). Anal.
Das Diaziridin (I) lagert sich beim Erhitzen in die Verbindung (II) um, die auch in 85%iger Ausbeute durch Behandlung von (I) mit Kalium‐tert.‐butylat erhalten werden kann.
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