A Highly Efficient Macrolactonization Method via Ethoxyvinyl Ester

摘要

We present the highly efficientreaction procedure of the macrolactonizationmethod via ethoxyvinylesters(EVEs).The following procedurewas performed:1)The EVE wasprepared from hydroxycarboxylic acid and ethoxyacetylene in the presence of the Ru catalyst [RuCl2ACHTUNGTRENUNG(p-cymene)]2 inacetone;2)after filtration of the Ru catalyst through a short-neutral SiO2pad and evaporation of acetone, the EVE formed was diluted in 1,2-dichloroethane(DCE)and the solution was slowly added by a syringe pump to the highly diluted DCE solution of pTsOH(10 mol%) at 80 8C.Varioussized lactones could be produced by the method described here.It is noteworthy that the method can give 9-to 14-membered macrolactones in goodyields.This macrolactonization methodvia EVEs is useful for acid-/base-sensitive substrates.Furthermore,it wasfound that EVE formation was possible without loosing activity of the Rucatalyst even for the compounds with nucleophilic amine functions.The characteristicfeature of the method was exemplifiedby the reaction of the compound14 with many functional groups.