Synthesis and Structural Investigation of an 鈥淥xazinoquinolinespirohexadienone鈥?That Only Exists as Its Long-Wavelength Ring-Opened Quinonimine Isomer

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• 作者：Benjamin J. Pollock ; Christos A. Sikes ; Ryan P. Ter Louw ; Scott R. Hawken ; Amy L. Speelman ; Eugene J. Lynch ; Daniel J. Stanford ; Kraig A. Wheeler ; Jason G. Gillmore
• 刊名：The Journal of Organic Chemistry
• 出版年：2012
• 出版时间：October 5, 2012
• 年：2012
• 卷：77
• 期：19
• 页码：8689-8695
• 全文大小：340K
• 年卷期：v.77,no.19(October 5, 2012)
• ISSN：1520-6904

文摘

The spirocyclic oxazinoquinolinespirohexadienone (OSHD) 鈥減hotochromes鈥?are computationally predicted to be an attractive target as electron deficient analogues of the perimidinespirohexadienone (PSHD) photochromes, for eventual application as photochromic photooxidants. We have found the literature method for their preparation unsuitable and present an alternative synthesis. Unfortunately the product of this synthesis is the long wavelength (LW) ring-opened quinonimine isomer of the OSHD. We have found this isomer does not close to the spirocyclic short wavelength isomer (SW) upon prolonged standing in the dark, unlike other PSHD photochromes. The structure of this long wavelength isomer was found by NMR and X-ray crystallography to be exclusively the quinolinone (keto) tautomer, though experimental cyclic voltammetry supported by our computational methodology indicates that the quinolinol (enol) tautomer (not detected by other means) may be accessible through a fast equilibrium lying far toward the keto tautomer. Computations also support the relative stability order of keto LW over enol LW over SW.