Synthesis and Ultraviolet Absorption Characteristics of Chiral 3- arylidenenopinones from β-pinene

Xu      Xu; Yi-Qin      Yang; Hai-Jun      Xu; Lan      Lan; Shi-Fa      Wang

Abstract

A new series of (1R,5R)-(-)-3-arylidenenopinones was synthesized from (1S,5S)-(-)-β-pinene which was a natural chemical from pine tree, and their ultraviolet absorption characteristics were investigated. (1R,5S)-(+)-nopinone was obtained from (1S,5S)-(-)-β-pinene by selective oxidation, and then it was reacted with benzaldehyde, phydroxybenzaldehyde, vanillin, o-vanillin, p-chlorobenzaldehyde, and p-methylaldehyde in the presence of alkali catalysts to get (1R,5R)-(-)-3-arylidenenopinones including (1R,5R)-(-)-3-benzylidenenopinone (1), (1R,5R)-(-)-3-(4′-hydroxybenzylidene) nopinone (2), (1R,5R)-(-)-3-(4′-hydroxy-3′-methoxybenzylidene)nopinone (3), (1R,5R)-(-)-3-(2′-hydroxy-3′- methoxybenzylidene)nopinone (4), (1R,5R)-(-)-3-(4′-chlorolbenzylidene)nopinone (5) (1R,5R)-(-)-3-(4′-methylbenzylidene) nopinone (6), and (1R,5R)-(-)-3-(furan-2′-ylmethylene)nopinone (7). The structures of (1R,5R)-(-)-3-arylidenenopinones were determined by FT-IR, ¹H NMR, ¹³C NMR and GC-MS techniques. Their ultraviolet absorption characteristics and light stability was further examined. The results showed that compounds 1, 2, 5, 6 and 7 could be used as B-type UV absorbents, and compounds 3 and 4 had both functions as UV-A and UV-B types absorbents because of their wide range of UV absorption at 200-390 nm and 280-290 nm respectively. The light stability sequence of these compounds was (6)≈(7)>(3)>(5)>(2)>(1)>(4).

Keywords: (1S, 5S)-(-)-β-pinene, (1R, 5S)-(+)-nopinone, (1R, 5R)-(-)-3-arylidenenopinones, Ultraviolet absorbent, Selective oxidation, Light stability.