On the photochemical dimerization of some 5-substituted 2-styryl-4-pyrones. The effect of 5-hydroxy-/ 5-methoxy-substitution

✍ Scribed by Zdenka Stiplošek; Marija Šindler-Kulyk; KreŠImir Jakopčić; Aleksandar Višnjevac; Biserka KojiĆ-ProdiĆ

• Publisher: Journal of Heterocyclic Chemistry
• Year: 2002
• Tongue: English
• Weight: 106 KB
• Volume: 39
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570390104

✦ Synopsis

Abstract

Irradiation of styryl‐4‐pyrones 1a‐1d or 2a‐2e (6‐9 × 10^−3^ M, methanol solution) with filtered (RAYONET photochemical reactor, 300 nm) or unfiltered uv‐light (high‐pressure mercury arc lamp) under aerobic conditions led mainly to dimeric products. Parent 5‐hydroxy‐substituted compounds 1a‐1d yielded exclusively “half‐cage” dimers 3a‐d characteristic for 4‐pyrone dimerization. 5‐Methoxy‐analogues 2a‐2e behave like typical stilbene structures and the mixture of tetrasubstituted cyclobutanes 4 and 5 accompanied with minor amount of phenanthrene‐like compound 6 were the only isolable products of the irradiation. The structure elucidation of products is based on spectral data obtained from MS, IR, ^1^H NMR and ^13^C NMR spectra applying COSY, APT, HETCOR, HMBC and NOESY techniques.