N-Halogeno compounds. Part 18. 1-Alkyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane salts: user-friendly site-selective electrophilic fluorinating agents of the N-fluoroammonium class

Methods of synthesis are described for a range of 1-alkyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane salts [R–N+(CH2CH2)3N+–F(X–)2, where R = CH3, CH2Cl, C2H5, CF3CH2, C8H17 and (X–)2=(TfO–)2, (BF4–)2, (PF6–)2, (TfO–, BF4–), (TfO–, PF6–), (TfO–, FSO3–)] by direct fluorination (with neat F2 at ⩽20 mmHg or F2–N2 blends at 1 atm pressure) of monoquaternary salts of 1,4-diazabicyclo[2.2.2]octane [R–+N(CH2CH2)3N X–] or their 1:1 adducts with boron trifluoride, phosphorus pentafluoride, or sulfur trioxide in acetonitrile at ca– 35 °C. The results of site-selective electrophilic fluorination of diethyl sodio(phenyl)malonate [→PhCF(CO2Et)2], 1-morpholinocyclohexene (→2-fluoro-cyclohexanone), phenol(→2-and 4-FC6H4OH), 1-and 2-hydroxynaphthalene (→2-and 4-FC10H6OH, and 1-FC10H6OH and 1,1-difluoro-2-oxo-1,2-dihydronaphthalene, respectively), acetanilide (→2-and 4-FC6H4NHCOCH3), anisole (→2-and 4-FC6H4OCH3) and sodium benzenesulfinate (→ PhSO2F) with these N-fluoroammonium salts are presented.