A new route is outlined for preparation of vinyl 1,2-diketones via a three-step sequence. First, allylic alcohols are photooxidized by O-2 to hydroperoxides, which are reduced to vinyl 1,2-diols. These vinyl 1,2-diols are oxidized to vinyl 1,2-diketones with oxoammonium salts, which are prepared in situ from organic nitroxyl radicals. The new route is short, avoids the use of protecting groups, and is generally applicable to obtain aliphatic or aromatic vinyl 1,2-diketones. (C) 2004 Published by Elsevier Ltd.
Exploratory studies toward the synthesis of the peroxylactone unit of plakortolides
作者:Bogdan Barnych、Jean-Michel Vatèle
DOI:10.1016/j.tet.2012.03.024
日期:2012.5
Our efforts in construction the 1,2-dioxane ring of plakortolides through two approaches are described. The first one involved as a key step an acid catalyzed 6-endo ring closure of beta-hydroperoxy trans-epoxides directed by a vinyl group adjacent to the epoxide function. By this route, an advanced intermediate of plakortolides was obtained in six steps and 35% overall yield. The second approach featured a 1,2-dioxane ring forming by a double opening of bis-epoxides by ethereal hydrogen peroxide. This reaction did not proceed in the expected sense and exclusive formation of hydroperoxy tetrahydropyran derivatives was observed via a tandem oxacyclization-hydroperoxidation sequence. (C) 2012 Elsevier Ltd. All rights reserved.