Benzene → trans-2-(4-Hydroxy-3-methoxy-5-nitrophenyl)-4-(3,4,5-trimethoxyphenyl)-1,3-dithiolane

Participants

Reaction Steps

1-(3,4,5-trimethoxyphenyl)-1,2-ethanedithiol (39) (FIG. 19) (25.4 g,97.7 mmole), 5-nitrovanillin (16.73 g, 84.9 mmole), pyridinium para-toluenesulfonate (PPTS) (8.52 g, 33.9 mmole) and 100 ml dry benzene were refluxed under an argon atmosphere with Dean-Stark removal of the benzene-water azeotrope for 12 hours. The reaction was cooled to room temperature and the precipitated PPTS removed by vacuum filtration. Hexane (100 ml) was added to the filtrate and the precipitate collected by vacuum filtration. The yellow solid was washed with cold water, followed by minimal cold methanol and finally cold diethyl ether to leave 28.62 g of a 1:1.3 cis/trans ratio of product. Six recrystallizations from ethyl acetate/hexane gives 4.3 g of pure trans diastereomer. An additional 2.4 g trans product can be obtained by repeating the above crystallization process from the material remaining in the mother liquors. Once 6.7 g of trans product was isolated,0.315 g of cis diastereomer was isolated by recrystallizing the combined mother liquors from above.

Provenance & Evidence