Ethyl propiolate → (3,4-Difluoro-phenyl)-propynoic acid ethyl ester

Participants

Reaction Conditions

Reaction Steps

Under argon atmosphere, a four neck flask was charged with THF (135 ml) and 2 M LDA in THF (60.9 ml, 0.12 mol, 1.18 eq.) and cooled to −78° C. Propynoic acid ethyl ester (12.2 g, 0.12 mol, 1.18 eq.) dissolved in THF (36 ml) was added dropwise within 30 min. Then, ZnBr2 (28.5 g, 0.12 mol, 1.2 eq.) dissolved in THF (45 ml) was added dropwise within 30 min. After the addition of 1,2-Difluoro-4-iodo-benzene (25.0 g, 0.10 mol) and tetrakis(triphenylphosphine) palladium(0) (6.02 g, 5.15 mmol, 5 mol %), the reaction mixture was allowed to warm to r.t. and stirred for another 3 h at the same temperature. The reaction mixture was diluted with diethylether and washed with saturated aqueous NH4I, saturated aqueous NaHCO3 and brine. The organic phase was dried with Na2SO4, concentrated under reduced pressure and dried under vacuum. The residue was purified by silica gel filtration (heptane/ethyl acetate 98:2) to yield 16.6 g (76%) of Vc as light yellow oil.

Provenance & Evidence