Photo-cycloaddition reactions of 2-pyrones.

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概要

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• Sensitized photoreactions of two 2-pyrones with five unsaturated compounds were investigated. The reactions of 2-pyrones with electron-deficient ethylenes gave [4+2]cycloadducts (<B>3</B>) and [2+2]cycloadducts (<B>4</B>) across the C<SUB>5</SUB>–C<SUB>6</SUB> double bonds in the 2-pyrones. On the other hand, reactions with an electron-donating ethylene, ethyl vinyl ether (<B>2i</B>), gave other kinds of [2+2]cycloadducts (<B>5</B>) and a [4+2]cycloadduct (<B>6</B>), site- and regio-selectively. These two kinds of reactions were inferred to start at the C-6 and C-4 positions of the 2-pyrones to give <B>3</B> or <B>4</B>, and <B>5</B> or <B>6</B>, respectively. The regioselectivity of <B>6</B> was opposite to that for a thermal [4+2]cycloadduct (<B>7</B>). The substituents on 2-pyrones also influenced the product-distribution and the triplet energy-level.

• 公益社団法人 日本化学会の論文

著者

• Suishu Takaaki

  Department of Applied Chemistry, Faculty of Engineering, Kagoshima University

関連論文

• Photo-cycloaddition reactions of 2-pyrones.

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