Department Chemie, Technische Universität München, Lichtenbergstr. 4, 85748 Garching, Germany.
Beilstein J Org Chem. 2012;8:1630-6. doi: 10.3762/bjoc.8.186. Epub 2012 Sep 26.
(E)-Alkyl ortho-hydroxycinnamates cyclize to coumarins at elevated temperatures of 140-250 °C. We find that the use of tri-n-butylphosphane (20 mol %) as a nucleophilic organocatalyst in MeOH solution allows cyclization to take place under much milder conditions (60-70 °C). Several coumarins were prepared, starting from ortho-hydroxyarylaldehydes, by Wittig reaction with Ph(3)P=CHCO(2)Me to (E)-methyl ortho-hydroxycinnamates, followed by the phosphane catalyzed cyclization.
(E)-烷基邻羟基肉桂酸酯在 140-250°C 的高温下环化生成香豆素。我们发现，在甲醇溶液中使用三正丁基膦（20mol%）作为亲核有机催化剂，可以在温和得多的条件下（60-70°C）实现环化反应。通过（E）-甲基邻羟基肉桂酸酯的 Wittig 反应，用 Ph(3)P=CHCO(2)Me 与邻羟基芳醛反应，然后用膦催化环化反应，从邻羟基芳醛出发，制备了几种香豆素。
