Heterocyclic polyfluoro-compounds. Part X. Nucleophilic substitution in tetrafluoropyrimidine

Abstract

Tetrafluoropyrimidine, prepared in high yield by reaction of tetrachloropyrimidine with anhydrous potassium fluoride at elevated temperatures, is highly susceptible to attack by nucleophiles; the ease of displacement of ring fluorines decreases in the order 4-and 6-> 2-5 5-. Through use of appropriate nucleophilic reagents the following fluoro-pyrimidines have been prepared : 4-X*C4F3N2 (X = OH), 4-YC4F3N2, and4,6-Y,*C4F,N2 (Y = NH,, OMe, NHPh. NHMe. or NMe,). and 2,4,6-Z,*C4FN, (2 = OMe). The structures of these compounds were established by nuclear magnetic resonance spectroscopy. Interpretation of the orientation of nucleophilic attack on tetrafluoropyrimidine and on pentafluoropyridine is provided.

Perhalogenated pyrimidine scaffolds. Reactions of 5-chloro-2,4,6-trifluoropyrimidine with nitrogen centred nucleophiles

“…Reaction of 1 with ammonia results in two isomeric products, as observed by 19 F NMR analysis of the reaction mixture which displayed two distinctive peaks (−48.18 and −69.47 ppm) for the 4-substituted isomer and one peak (−65.44 ppm) for the 2-isomer in a 9 : 1 ratio, the chemical shifts being consistent with previous studies [ 18 ]. Similarly, reaction of 1 with ethylamine gives two isomers in an 8 : 1 ratio by 19 F NMR as shown by the appearance of two fluorine signals (−47.48 and −70.83 ppm) and one signal (−63.59 ppm) corresponding to the 4- and 2-amino isomers respectively.…”

“…Whilst 1 is commercially available and has been known for some time, only a limited number of reactions have been reported (e.g. with ammonia to give the 4-amino derivative [ 18 ]) despite the fact that 1 is used widely in the fibre reactive dye industry [ 19 ]. However, a systematic study of the reactivity of this potentially valuable scaffold with other nitrogen nucleophiles has not been reported.…”

Sky-blue emitting bridged diiridium complexes: beneficial effects of intramolecular π–π stacking

“…meta ( 4 J) 19 F- 19 F coupling constants that are considerably smaller than those for ortho and para coupling (or even absent) have been commonly reported for heavily fluorinated aryl systems. [39][40][41][42][43] It has been suggested that this is because π-conjugation contributes significantly to 19 F- 19 F coupling in aromatics. 39,43 We propose that this restriction of rotation is due to intramolecular π-π interactions.…”

Polychloroheteroaromatic Compounds

“…Tetrachloropyrimidine may be converted into 5-chlorotrifluoropyrimidine by reaction with silver fluoride [578] or into the perfluoro-compound by reaction with anhydrous caesium or potassium fluoride, preferably at elevated temperatures (410-480°) in an autoclave [214,569,583] . When the perchloro-compound is reacted with hydrofluoric acid in a nickel autoclave at 130° for 10 h, it yields a mixture of 5-chlorotrifluoropyrimidine (6%), a dichlorodifluoropyrimidine (39%), which is probably the 5,6-dichloro-2,4difluoro-compound, and a trichlorofluoropyrimidine (47%), which is probably trichloro-4-fluoropyrimidine [584] .…”

“…2,4,6-Trichloropyrimidine is converted into 2,4,6-trifluoropyrimidine on treatment with potassium [583,[585][586][587] or silver fluoride [531,578,588]. Lower fluorinated products may be formed also, depending on the reaction conditions.…”