Synthesis and Photochromic Properties of New Heterocyclic Derivatives of 1,3-diazabicyclo[3.1.0]hex-3-ene Nosrat O. Mahmoodi,* Mohammad R. Yazdanbakhsh, Hamzeh Kiyani and Bahman Sharifzadeh Chemistry Department, Faculty of Science, Guilan University, P.O. Box 41335-1914, Rasht, Iran The facile synthesis of several 1,3-diazabicyclo[3.1.0]hex-3-ene derivatives with varying substitu- tions such as 2-methyl-6-(4-nitrophenyl)-2,4-diphenyl-(1), 2-methyl-6-(4-nitrophenyl)-4-phenyl-2- (pyridin-3-yl)-(2), 2-(furan-2-yl)-6-(4-nitrophenyl)-4-phenyl-(3), 2-(furan-2-yl)-6-(3-nitrophenyl)-4- phenyl-(4), 6-(3-nitrophenyl)-2,4-diphenyl-(5) and 6-(4-chlorophenyl)-4-(3-nitrophenyl)-2-phenyl-(6) that all behave as “intelligent materials” are reported. Keywords: Aziridine ring; Imine ylide; 1,3-diazabicyclo[3.1.0]hex-3-ene derivatives; Intelligent material; Photochromism. INTRODUCTION Photochromism is a vast field encompassing well- known phenomena associated with reversible transforma- tions a and b, having different absorptions upon irradiation with UV and visible light (Fig. 1). Functionalized aziridines are an extremely important class of compounds; as they are precursors of new biologi- cally active compounds, they are very useful synthetic in- termediates. 1 Study of photochromic materials has drawn great at- tention to their significant application in optical data stor- age, holographic storage, solar cells, and as sensitizers. In this chemical process, a compound undergoes a reversible change between two states having separate absorption spectra, i.e. different colors. Typical photochromic optical switching devices include ophthalmic and sunglass lenses. 2,3 Various photochromic dyes have been developed to im- prove major photochromic properties such as reversibility and stability. Examination of new methods of the synthesis of aziridine derivatives has therefore attracted considerable attention, and the search for a means of rapid access to these heterocycles and their diverse biological properties is well documented in the literature. 4 RESULTS AND DISCUSSION Our research in this area has been concerned with the synthesis of 1,3-diazabicyclo[3.1.0]hex-3-ene derivatives with varying substitutions and their application as photo- chromics and in photoreproduction. 5 The synthesis of sev- eral fluorescence emission producers based on symmetri- cal and unsymmetrical trisannelated benzene constructions and several related photochromic compounds was at- tempted. 6,7 Here we describe an effiecient approach to the synthesis of stereodefined bridgehead aziridines 1-6 (Fig. 2) with varying heterocyclic substitutions at the 2-position. According to the recorded UV-Vis spectra all are consid- ered as positive photochromism compounds and behave as intelligent materials. 8 Currently, there are no published data available on the synthesis of 1-4 with the heterocyclic moieties at the 2 po- sition of imidazol (d ring, Fig. 3). Synthesis of compound 6 with substitution on the b ring for the first time is reported. A synthesis sequence for the preparation of the precursor aziridine 12c has not been previously reported (Scheme II). In our approach to aziridine 12c, the dibromination of 8 Journal of the Chinese Chemical Society, 2007, 54, 635-641 635 * Corresponding author. E-mail: Mahmoodi@guilan.ac.ir N N Ar 3 H Ar 1 Ar 2 R N N Ar 3 H Ar 1 Ar 2 R a b hv 1 hv 2 Fig. 1