A convenient synthesis of linear 2-methylpyranochromones.
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概要
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A convenient synthesis of linear 2-methylpyranochromones, <I>viz.</I>, spatheliachromen(5-hydroxy-2,2,8-trimethyl-2<I>H</I>,6<I>H</I>-benzo[1,2-<I>b</I>:5,4-<I>b</I>′]dipyran-6-one), <I>O</I>-methylspatheliachromen (5-methoxy-2,2,8-trimethyl-2<I>H</I>,6<I>H</I>-benzo[1,2-<I>b</I>:5,4-<I>b</I>′]dipyran-6-one) (<B>8</B>) and <I>O</I>-methylallopteroxylin (5-methoxy-2,8,8-trimethyl-4<I>H</I>,8<I>H</I>-benzo[1,2-<I>b</I>:3,4-<I>b</I>′]dipyran-4-one) is described by blocking the eighth position of the corresponding 7-propargyl ether derivative 7-(1,1-dimethyl-2-propynyloxy)-8-iodo-5-methoxy-2-methyl-4<I>H</I>-1-benzopyran-4-one with iodine followed by thermal cyclization. The linear pyranochromones 2,2,8-trimethyl-2<I>H</I>,6<I>H</I>-benzo[1,2-<I>b</I>:5,4-<I>b</I>′]dipyran-6-one and <B>8</B> are also synthesized starting with the easily available appropriate 3,4-dihydro-2,2-dimethyl-2<I>H</I>-1-benzopyran-7-ols following the steps of Claisen condensation with ethyl acetate, cyclization with ethanolic sulfuric acid followed by dehydrogenation with NBS.
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著者
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Jain Anjula
Department of Chemistry, University of Delhi
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Ahluwalia Vinod
Department of Chemistry, University of Delhi
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Gupta Ranjna
Department of Chemistry, University of Delhi