Cesium carbonate → (3,4-Dichloro-phenyl)-propynoic acid ethyl ester

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

Under argon atmosphere, a four neck flask was charged with 1,2-dichloro-4-iodo-benzene (222.8 g, 0.80 mol), bis(triphenylphosphine) palladium(II) chloride (11.2 g, 16.0 mmol, 2 mol %), copper(I) iodide (6.09 g, 32.0 mmol, 4 mol %) and dry THF (2.4 l). At r.t., cesium carbonate (526.6 g, 1.60 mol, 2 eq.) was added over 5 minutes. Afterward, propynoic acid ethyl ester (168.6 ml, 1.60 mol, 2 eq.) was added, and the reaction mixture was stirred overnight at 35° C. An additional portion of propynoic acid ethyl ester (17.0 ml, 0.16 mol, 0.2 eq.) was added, and the reaction was stirred for another 4 h at 35° C. The reaction mixture was evaporated to dryness, and the residue was taken up in toluene (0.8 l) and heptane (1.6 l). The resulting suspension was stirred at 40° C. for 1 h and filtered over celite. The filtrate was concentrated, and the product was purified by silica gel filtration (toluene/heptane 1:2) to yield 175.0 g (89%) of Vb as a white solid.

Herkunft & Nachweise