CYCLOPROPYLDIPHENYLSULFONIUM FLUOROBORATE

B. Preparation of Cyclopropyldiphenylsulfonium Fluoroborate. A suspension of 118.7 g. (0.339 mole) of 3-chloropropyldiphenylsulfonium fluoroborate (Note 2) in 500 ml. of dry tetrahydrofuran (Note 12) is placed in a 2-1., one-necked flask equipped with a magnetic stirring bar and nitrogen inlet tube under nitrogen. Then 5-g. portions of 55% sodium hydride-mineral oil dispersion (15.2 g., 0.350 mole) are added in 30-minute intervals. The resulting mixture is stirred (Note 13) at room temperature for 24 hours. An aqueous solution of 25 ml. of 48% fluoroboric acid (Note 14), 15 g. of sodium fluoroborate (Notes 7, 15), and 400 ml. of water is added to the well-stirred reaction to destroy residual hydride and swamp out chloride ion (Note 16). After 5 minutes 300 ml. of methylene chloride is added, and the top methylene chloride layer is removed from the lower aqueous layer (Note 17). The methylene chloride solution is then extracted with 100 ml. of water. This water layer is combined with the first aqueous layer, and the combined water layers are extracted with an additional 100 ml. of methylene chloride. The methylene chloride portions are combined, dried over anhydrous sodium sulfate, and evaporated at reduced pressure until precipitation occurs. Addition of 1 1. of ether completes the precipitation of the salt. 

Cyclopropanes, 101, 267 Cyclopropanone ketals, 315-316 Cyclopropene, 113 Cyclopropenone, 519 Cyclopropenones, 27, 399 Cyclopropylacetylene, 401 Cyclopropyl azides, 323 Cyclopropylcarbinyl compounds, 53 Cyclopropyldiphenylsulfonium fluoroborate, 211,213-214... 

Oxaspiropentanes.3 Oxaspiropentanes (2) were suggested as intermediates in the synthesis of cyclobutanones formulated above. These have now been isolated in about 60-80 % yield by treatment of a carbonyl compound with cyclopropyldiphenylsulfonium fluoroborate (l)4 and solid potassium hydroxide at 25° in DMSO followed by flash distillation of the crude extract under vacuum. 

Epoxy-5,5-dimethylcyclohexanone allowed to react 2 hrs. at 25 with 1.25 equivalents cyclopropyldiphenylsulfonium fluoroborate and 2 equivalents KOH in dimethyl sulfoxide -> diepoxide (Y 96%) dissolved in pentane and washed with aq. 1 M fluoroboric acid epoxycyclobutanone deriv. (Y ca. 100%) (startg. m. f. 101). - This sequence can be used as part of an annelation process complimentary to the normal Robinson method. F. e., rearrangement also with oxalic acid, s. B. M. Trost and M. J. Bogdanowicz, Am. Soc. 94, Mil (1972) lactone annelation cf. Tetrah. Let. 1973, 923 Am. Soc. 95, 5321 (1973) replacement of carbonyl oxygen by 2 functionalized carbon substituents cf. Am. Soc. 95, 2038, 7862 (1973). 

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