Sulfuric Acid → 1,1-Bis(2-methoxyphenyl)cyclopropane

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Reaction Steps

Sodium hydride (4.4 g of 60 percent oil dispersion) was placed in a flask with 140 ml of dimethoxyethane. This mixture was cooled with an ice bath and 22.3 g of triethyl phosphonoacetate was added dropwise with stirring over a 30 min period. A murky yellow solution was obtained. 2,2'-Dimethoxybenzophenone (20.2 g) was added and the resulting mixture was heated at reflux with stirring for 20 hours. It was then allowed to cool to ambient temperature and was diluted with 500 ml of ether. The resulting mixture was washed with 3-200 ml portions of 1N hydrochloric acid and with saturated sodium bicarbonate, dried over magnesium sulfate, filtered, and concentrated by evaporation under reduced pressure to obtain a turbid, viscous yellow oil. This material was found by gas chromatagraphy to be about 79 percent one compound. It was dissolved in 100 ml of tetrahydrofuran and the solution added dropwise with stirring to a slurry of 4.70 g of lithium aluminum hydride in 100 ml of tetrahydrofuran over a 40 min period. An exothermic reaction ensued. The mixture was heated at reflux for 3 hours and allowed to stand at ambient temperature overnight. About 100 ml of 10 percent sulfuric acid was added carefully with stirring to quench the excess lithium aluminum hydride. About 700 ml of ether was then added and the layers were separated. The ether layer was extracted with water, 10 percent hydrochloric acid, 10 percent potassium hydroxide, and brine. It was then dried over magnesium sulfate, filtered, and concentrated by evaporation under reduced pressure. The residue was purified by filtration chromatography on silica eluting with a 10:90 mixture of ether and hexane. The solvents were removed by evaporation under reduced pressure to obtain 5.6 g (26 percent of theory) of the title compound as pale yellow crystals melting at 146°-149° C. The carbon-13 and proton nmr spectra were in agreement with the assigned structure.

Provenance & Evidence