Synlett 2005(16): 2473-2477  
DOI: 10.1055/s-2005-917082
LETTER
© 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
Fax: +6563166984; e-Mail: teckpeng@ntu.edu.sg;
Further Information

Publication History

Received 31 May 2005
Publication Date:
21 September 2005 (online)

Abstract

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.

8

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

9

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

10

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

11

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.

12

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.