The Reactions of Sequence

The synthesis begins with an aldol reaction between 4-nitrobenzaldehyde and acetophenone in Experiment [FI] to )ield 4-nitrochalcone  

The chalcone is brominated in the second step (Experiment [F2]) to )4eld eryflzro-2,3-dibromo-3-(4-nitrophenyl)propiophenone  

When this halogenated compound is treated with ethanolic ammonium hydroxide for several days, as in Experiment [F3], the system undergoes several reactions (dehydrohalogenation, amination, and ring closure) to ultimately yield a trans-substituted aziridine product  

The photochromic substance, a diazabicyclo[3.1.0]hex-3-ene, is obtained in the fourth step (Experiment [F4]) when the aziridine is treated with ben-zaldehyde, anhydrous ammonia, and ammonium bromide. The reaction requires several days to go to completion. 

The product is a colorless crystalline substance that possesses the property of turning a deep blue when exposed to indoor light  

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