First direct synthesis of 3-hydroxy-pent-4-ynoic acids. Application to the synthesis of pyran-2-ones
作者:Morelia E. López-Reyes、José G. López-Cortés、M. Carmen Ortega-Alfaro、R. Alfredo Toscano、Cecilio Alvarez-Toledano
DOI:10.1016/j.tet.2013.06.069
日期:2013.9
We describe a direct method for the synthesis of 3-hydroxy-pent-4-ynoic acids by the nucleophilic addition of bis-(TMS) ketene acetals to alkynones promoted by BF3 center dot Et2O. A systematic study involving electron withdrawing and electron donor groups (R-1=NO2, CF3, Br, Cl, H, Me, OMe) in the propargyl ketone reveals a strong dependence of electronic effects on the regiochemistry of the nucleophilic addition. Using a halolactonization protocol, we demonstrated the synthetic potential of these acids by their efficient transformation into new 5-bromo-3,4-dihydro-2H-pyran-2-ones. (C) 2013 Elsevier Ltd. All rights reserved.