Efficient method for the lactonization of ω-hydroxycarboxylic acids with di-2-thienyl carbonate by the promotion of catalytic amounts of DMAP and Hf(OTf)4
An efficient method for the synthesis of macrolides from ω-hydroxycarboxylic acids is established by using an equimolar amount of di-2-thienyl carbonate (2-DTC) and catalytic amounts of 4-(dimethylamino) pyridine (DMAP) and group 4 metal triflates such as hafnium(IV) trifluoromethanesulfonate (Hf(OTf)4). Copyright
New and efficient method for the preparation of medium-sized lactones from the corresponding ω-hydroxycarboxylic acids
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).
Mukaiyama, Teruaki,Izumi, Jun,Shiina, Isamu
p. 187 - 188
(2007/10/03)
Scandium trifluoromethanesulfonate as an extremely active Lewis acid catalyst in acylation of alcohols with acid anhydrides and mixed anhydrides
Scandium trifluoromethanesulfonate (triflate), which is commercially available, is a practical and useful Lewis acid catalyst for acylation of alcohols with acid anhydrides 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 acid anhydrides of not only primary alcohols but also sterically-hindered secondary or tertiary alcohols. The method presented is especially effective for selective macrolactonization of ω-hydroxy carboxylic acids.
A New Synthetic Method of Macrocyclic Lactones from ω-Iodoalkylacrylates
When the photostimulated cyclization reaction of ω-iodoalkylacrylates was performed in the presence of metal hydride complexes such as sodium cyanoborohydride (NaBH3CN), sodium borohydride (NaBH4) and potassium borohydride (KBH4), the corresponding macrocyclic lactones were produced.The use of NaBH3CN led to the highest yield of lactones.
Abe, Motoji,Hayashikoshi, Takaoki,Kurata, Takeo
p. 1789 - 1792
(2007/10/02)
Facile Synthesis of Lactones from Silyl ω-Siloxycarboxylates Using p-Trifluoromethylbenzoic Anhydride and a Catalytic Amount of Active Lewis Acid
The lactonization of silyl ω-siloxycarboxylates is successfully carried out under mild conditions in good to high yields by using p-trifluoromethylbenzoic anhydride and a catalytic amount of active acidic species generated in situ from TiCl4 and AgClO4.