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Utilizing an enaminoketone (1) as starting material, 3-substituted chromones were synthesized by the reactions of acid anhydrides derivatives under mild conditions.

In the presence of SnCl 4 , α,β-epoxy alcohol derivatives easily reacted with allylsilanes to give the corresponding tetrahydrofurans in moderate yields.

In the presence of a Lewis acid, cyclopropapyranones easily reacted with silyl enolates to give the 4-oxepanones in good yields. In this reaction, the trans-isomer was mainly obtained.

Heterocycles, 55, 855-859 (2001). Synthesis of Trisubstituted 4-Oxepanones by the Lewis Acid-Promoted Three-Component Ring-Expansion Reaction of Cyclopropapyranones, Silyl Enolates and Glyoxylates Yoshiaki Sugita(杉田義昭)*, Chikasa Kimura(木村爾沙), and Ichiro Yokoe (横江一朗) Faculty of Pharmaceutical Sciences, Josai University, Sakado, Saitama 350-0295 In the presence of SnCl4, cyclopropapyranones easily reacted with the silyl enolates and ethyl glyoxylate to give the trisubstituted 4-oxepanones in good yields with moderate stereoselectivity. In all the reactions, the trans-E-isomer was mainly obtained.

The treatment of cyclopropanes having donor and acceptor substituents at the vicinal positions on the cyclopropane ring with a Lewis acid readily generates a 1,3-zwitterion, which reacted with allylsilanes to produce cycloadducts and allylic products. It was found that the yield of the cycloadduct depends on the steric demand of the alkyl substituents on the silicon atom.

We describe a convenient preparation of isoflavones by the cross-coupling reactions of 3-iodo-chromone (1) with arylboronic acids (2) catalyzed by tetrakis(triphenylphosphine)palladium(0).