Selective fluorination of dispiro[3.1.3.1]decan-5,10-dione by diethylaminosulfurtrifluoride to give 10,10-difluorodispiro[3.1.3.1]decan-5-one and 5,5,10,10-tetrafluorodispiro[3.1.3.1]decane

Dispiro[3.1.3.1]decan-5,10-dione was selectively difluorinated at room temperature by diethylaminosulfur trifluoride (DAST) to give 10,10-difluorodispiro[3.1.3.1]decan-5-one. The latter was reduced to 5,5-difluorodispiro[3.1.3.1]decane and also reacted with excess DAST to give 5,5,10,10-tetrafluorodispiro[3.1.3.1]decane. Proton and fluorine magnetic resonance studies on 5,5-difluorodispiro[3.1.3.1]decane did not show significant cross-ring coupling (< 0.5 Hz) between geminal fluorines on C-5 and geminal hydrogens on C-10. The fluorine magnetic resonance spectrum of 5,5,10,10-tetrafluorodispiro[3.1.3.1]decane was a single sharp line which establishes that through-space coupling between geminal fluorines at C-5 and C-10 and geminal hydrogens on other carbons does not exist. A study of the infrared and ultraviolet spectra of dispiro[3.1.3.1]-decane-5,10-dione indicate the cross-ring carbonyl groups interact significantly.