To a magnetically stirred, ice-cooled solution of p-dimethylaminobenzoyl chloride (0.02 mole) and triethylamine (20 ml) in methylene chloride (300 ml) under an argon atmosphere was added dropwise a solution of 4-(9-thioxanthylidene)-piperidine (0.0133 mole) in methylene chloride (100 ml) over a twenty minute period. After stirring for 48 hours at room temperature, water (250 ml) was added and the mixture stirred for an additional 30 minutes. The layers were separated and the organic layer was washed with water (100 ml), 5% sodium hydroxide (2×200 ml) and water (250 ml), and then dried over sodium sulfate, filtered and stripped under reduced pressure to a dark orange oil. The product was purified by low pressure column chromatography using a 25×1000 mm column packed with 250 g. of silica gel absorbent and eluted with ethyl acetate to yield 2.3 grams of the product. Recrystallization from toluene yielded 2.1 g. of product, m.p. 178°-186° C. (decomp.)
