Phase Transfer-Catalyzed Dehydrohalogenation PropiolaLdehyde Diethyl Acetal

Submitted by A. Le Goq andA. Gorgues Checked by G. Saucy and P. S. Manchand [Pg.10]

3-Dibromopropionaldehyde diethyl acetal. A 500-ml., three-necked, round-bottomed flask is equipped with a mechanical stirrer, a pressure-equalizing dropping funnel fitted with a calcium chloride drying tube, and a thermometer. The flask and dropping funnel are charged with 28.0 g. (0.5 mole) of freshly distilled acrolein and 80.0 g. (0.5 mole) of bromine, respectively. The acrolein is stirred rapidly and cooled to 0° in an ice-salt bath, then bromine is added at a rate such that the temperature is kept at [Pg.10]

until a permanent red color indicates a slight excess of bromine in the flask. A total of 78-79 g. of bromine is added over a [Pg.10]

1- hour period. The crude 2,3-dibromopropionaldehyde is stirred while a solution of 80 g. (0.54 mole) of freshly distilled triethyl orthoformate in 65 ml. of absolute ethanol (Note 1) is added over 15 minutes. The solution warms to 45° and is stirred for 3 hours, after which ethyl formate, ethanol, and triethyl orthoformate are removed on a rotary evaporator. Distillation of the residual liquid through a 15-cm. Vigreux column affords 107-112 g. (74-77%) of 2,3-dibromopropionaldehyde diethyl acetal, b.p. 113-115° (11 mm.), as a pale-yellow liquid (Note 2). [Pg.10]

Absolute ethanol from a commercial supplier was used without further treatment. [Pg.11]

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