Synlett 2005(16): 2473-2477  
DOI: 10.1055/s-2005-917082
© Georg Thieme Verlag Stuttgart · New York

Synthesis and Photochromic Properties of Cycloalkylidene Fulgides

Wei-Woon Wayne Leea,b, Leong-Ming Ganb, Teck-Peng Loh*c
a Department of Chemistry, 3 Science Drive 3, National University of Singapore, 117543, Singapore
b Institute of Materials Research and Engineering, 3 Research Link, 117602, Singapore
c Division of Chemistry and Biological Chemistry, Nanyang Technological University, 637616, Singapore
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Received 31 May 2005
21. September 2005 (online)


A series of cycloalkylidene fulgides have been synthesized using β,γ-unsaturated diesters, instead of the usual α,β-unsaturated diesters. A study of their photochromic properties revealed that an increase in the cycloalkylidene ring size caused a subsequent decrease in the formation of the closed form from the open form.


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The observation of the migration of the double bond was also reported then.


Compound 10 was obtained in 40% yield and 8 in 9% yield, respectively.


As determined from crude 1H NMR of the reaction mixture.


Attempts to obtain the cyclooctylidene succinic diester resulted in the self-condensed product from the cyclooctanone, which was only determined from crude 1H NMR and not isolated. The cyclopentanone used to obtain 11 also tends to afford the self-condensed product quite readily.


This was to ensure the complete formation of the diacid and to maximize yield. Yields of synthesized fulgides were much lower when this step was omitted.