Under argon, 2.12 g (5 mmol) of 1,1-diethyl-3-[2-(1,3-dithiolan-2-yl)-6-methyl-8ergolinyl]urea is dissolved in 40 ml of chloroform. Then 3.5 g of silica gel is added and, under vigorous agitation, 3.5 ml of water is introduced dropwise. During a time period of 30 minutes, a solution of 1.18 ml of sulfuryl chloride in 30 ml of chloroform is added dropwise. After 3 hours of agitation at room temperature, 7.5 g of potassium carbonate is added and the mixture vigorously stirred for 20 minutes. The precipitate is filtered off and rinsed with chloroform. The precipitate is moistened with ethanol and introduced into 300 ml of saturated sodium chloride solution which is then repeatedly extracted with chloroform. The chloroform extracts and the chloroform filtrate are dried together over magnesium sulfate and evaporated. Subsequent crystallization takes place from ethyl acetate, thus isolating 1.16 g of 1,1-diethyl-3-(6-methyl-2-formyl-8α-ergolinyl)urea (61% yield).
