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
di-2-thienyl carbonate (2-DTC) in the presence of a catalytic amount of 4-(dimethylamino)pyridine (DMAP) proceeded smoothly to afford the corresponding esters in good-to-high yields along with 2(5H)-thiophenone. This esterification was accelerated by the addition of an equimolar amount of iodine to afford the esters in higher yields within a shorter reaction time. Further, cyclization of ω-hydroxycarboxylic
Macrocyclisation of Macrodiolide with Dimethylaluminium Methaneselenolate
作者:Liu-Lan Shen、Han-Seo Mun、Jin-Hyun Jeong
DOI:10.1002/ejoc.201001201
日期:2010.12
Dimethylaluminium methaneselenolate (Me 2 AlSeMe, 1) acts as an acyltransferagent for esterification. In cases of direct macrolactonisation (n = 10-12), this selenium-aluminium complex preferentially creates symmetric macrodiolides rather than macrolides. The factors determining macrodilactonisation were investigated and applied toward the total synthesis of norpyrenophorin, which result in a macrodilactonisation
New and Efficient Method for the Preparation of Medium-sized Lactones from the Corresponding<i>ω</i>-Hydroxycarboxylic Acids
作者:Teruaki Mukaiyama、Jun Izumi、Isamu Shiina
DOI:10.1246/cl.1997.187
日期:1997.2
Medium-sized lactones are prepared in good yields on treating monomeric cyclic silyl siloxycarboxylates, prepared in situ from ω-hydroxycarboxylic acids and 1,2-bisdimethylsilylbenzene using RhCl(PPh3)3 catalyst, with an active catalyst of dimethylsilylbis(trifluoromethanesulfonate).