It has been reported by I.M. Heilbron et al that installing ortho- and para-methoxy groups on the ring affected the photochromicity of cinnamaldehyde semicarbazone. Our study sought to explore the photochromicity of related cinnamaldehyde semicarbazones, synthesized in 3 steps via condensation of the Wittig reagent ((1,3-dioxolan-2-yl)methyltriphenylphosphonium bromide) with different aldehydes, hydrolysis of the acetal, and formation of the imine. This afforded a variety of di-and tri-methoxycinnamaldehydes in 53-88% yields, polycyclic analogs in 31-57% yields, and heteroaromatic analogs in 40-69% yields. Although extended cinnalmaldehydes were obtained by recycling the aldehyde products back through the sequence, a convergent approach starting from but-2-ene-1,4-diol was explored. After monoprotection with an acetyl group, the remaining alcohol was converted to a bromide for a subsequent Arbuzov reaction with triethylphosphite to give the 4C phosphonate. This was then oxidized and condensed with benzaldehydes and cinnamaldehydes. All intermediates and products were characterized by 1H and 13C NMR spectroscopy, and attempts at evaluating the photochromicity were carried out using UV-VIS spectroscopy.

Synthesis of cinnamaldehyde semicarbazones and their photochromicity

247th National Meeting (2014)

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