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Paper | Regular issue | Vol 32, No. 4, 1991, pp.749-757
Published online, 1st January, 1970
DOI: 10.3987/COM-91-5687
Reaction of Alkyl Radicals with γ-Pyron Derivatives, 2-Methoxycarbonylchromone and Dimethyl Chelidonate.

Masaru Tada* and Naruo Mori

*Department of Chemistry, School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan


The reaction of alkyl radicals with 2-methoxycarbonylchromone (3) and dimethylchelidonate (4) gave dimeric products, 2,2’-bis -(2,2’-dimethoxycarbonyl-3,3’-dialkyl)chromanone (5 and 6) and 2,2’-(bis-2,2’,6,6’-tetramethoxycarbonyl-3,3’-dialkyl)-2,3-dihydro-4-oxo-4H-γ-pyran (8 and 9). Both the dimeric products consist of two stereoisomers, meso and dl at the central bond of the dimer. The formation of the dimeric products is accounted for by the initial attack of alkyl radical to the α-position of the γ-pyrone derivatives having ester group at β-position. The intervention of the capto-dative radicals is supported by the thermal equilibrium with the dimeric products.