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Paper | Regular issue | Vol 102, No. 2, 2021, pp.254-273
Published online, 6th January, 2021
DOI: 10.3987/COM-20-14391
■ [2+2]Photocycloaddition of 5,6-Substituted 2-Oxo-2H-pyran-3-carboxylates with Alkenes

Yun-Han Hsieh, Hiroki Iwasaki, Yumina Iwai, Miki Adachi, Kanako Kitai, Eri Kuribayashi, Yuri Hirata, Suzuna Sakaguchi, Naoko Sakaguchi, Naoto Kojima, and Masayuki Yamashita*

*Kyoto Pharmaceutical University, 1 Misasagi-Shichono-cho, Yamashina, Kyoto 607-8412, Japan

Abstract

The [2+2]photocycloaddition of alkenes and 5,6-substituted 2-oxo-2H-pyran-3-carboxylates with an ester as an electron-withdrawing group was developed. The 3,4-adducts, 4,5-disubstituted 3-oxa-2-oxobicyclo[4.2.0]oct-4-ene-1-carboxylates, were obtained in moderate yields accompanied by considerable amounts of the 5,6-adducts, 1,6-disubstituted 2-oxa-3-oxobicyclo[4.2.0]oct-4-ene-4-carboxylates. These structures, including their stereochemistry, were determined by various spectral and computational analyses, and some were examined by X-ray crystallographic analysis. The determined regio- and stereoselectivities were explained by frontier orbital theory.