Synthesis of New Halo-Containing Enynes: Reaction of Lithium Acetylenides with 1,1,1-Trihalo-4-alkoxy-3-buten-2-ones

The reaction of lithium acetylenide ((R-C°CLi, where R = Ph, Pent, Bu) with 1,1,1-trihalo-4-alcoxy- 3-alken-2-ones [CX3C(O)C(R2)=C(R1)-OR3, where X = Cl, F; R1, R2 = H, Me; R3 = Me, Et] in the presence of BF3·Et2O to give 1,4- or 1,2-addition products is reported. The regiospecific formation of 1,4-addition products was observed for substrates with R1 = H, and for substrates which had the methyl group on C-4 (R1 = Me), the formation of 1,2-addition products was favored.