A Reagent for Selective Deprotection of Alkyl Acetates
摘要:
The use of magnesium methoxide for selective deprotection of alkyl esters is described. By adjusting the equivalents of the magnesium methoxide reagent, it is possible to selectively cleave primary acetate in the presence of secondary and tertiary acetate and to cleave secondary acetate in the presence of tertiary acetate. A high selectivity can also be obtained for the same primary acetates if the beta-positions of the acetates render a different steric bulkiness. This mild reagent has been successfully applied to the selective deprotection of many natural-occurring molecules including hydroxycitronnellol diacetate, trans-sobrerol diacetate, betulin diacetate, and baccatin III.
RECYCLABLE CATALYSTS FOR ESTERIFICATION OR ACYLATION OF ALCOHOLS
申请人:LU NORMAN
公开号:US20120184748A1
公开(公告)日:2012-07-19
A compound is useful as a recyclable catalyst for esterification or acylation of alcohols and consists of saccharine and a compound comprising a pyridine moiety. In addition, also a method of preparing the compound and an ester synthesis method using the compound are introduced.
Pyridinium saccharinate salts as efficient recyclable acylation catalyst: a new bridge between heterogeneous and homogeneous catalysis
作者:Norman Lu、Wei-Hsuan Chang、Rong-Jyun Wei、Yung-Cheng Fang、Tu-Wen Han、Guo-Quan Wang、Jia-Yaw Chang、Yuh-Sheng Wen、Ling-Kang Liu
DOI:10.1016/j.tet.2016.04.073
日期:2016.6
The homogeneous nature of DMAP-catalyzed acylation still suffers from the problems of catalyst separation and/or residual DMAP contamination. DMAP causes acute dermal toxicity, whereas the corresponding DMAP salt exhibits only slight irritation to the skin. Very recently, we found that the DMAP saccharinate salt is also great recyclablecatalyst, whose acylation of alcohols has been successfully and effectively
catalytic condensation of carboxylic acids with equimolar amounts of alcohols is the most desirable. Although several highly active dehydration catalysts have been reported, more efficient alternatives are still strongly needed because the dehydrative esterification of tertiary alcohols, phenols, acid-sensitive alcohols, amino acids, and hardly soluble alcohols has never proceeded satisfactorily. Here
Erbium(III) triflate is a powerfulcatalyst for the acylation of alcohols and phenols. The reaction works well for a large variety of simple and functionalized substrates by using different kinds of acidicanhydrides Ac2O, (EtCO)2O, [(CH3)3CO]2O, Bz2O, and (CF3CO)2O} without isomerisation of chiral centres. Moreover, the catalyst can be easily recycled and reused without significant loss of activity
is commercially available, is a practical and useful Lewis acidcatalyst for acylation of alcohols with acidanhydrides or the esterification of alcohols by carboxylic acids in the presence of p-nitrobenzoic anhydrides. The remarkably high catalytic activity of scandium triflate can be used for assisting the acylation by acidanhydrides of not only primary alcohols but also sterically-hindered secondary