Abstract 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 BF 3· Et 2 O. A systematic study involving electron withdrawing and electron donor groups (R 1= NO 2, CF 3, 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 ...
