Reactions of polyfluorobenzenes with nucleophilic reagents

Abstract

Nucleophilic reactions of hexafluorob enzene and related polyfiuorobenzenes were studied in detail. R eaction of hex a fluorobenzc nc with hydroxides, alco holates, aqueous amines, and organolithium co mpounds led to the substitution of one 01' more fluorine atoms. The stru ctures of the products were determined, using near infra red a nd nuclear m agnetic resonance spectra. Fluorine is replaced more readily than chlorin e, bromine, iodine, or other groups. I n the ma jo rity of the products in which two of the fluorin es in hexafluorobenzene we re replaced, t he substituting groups were p a ra to eac h other. However, depe nding on the reagents other orientation effects were noted . The reaction mechanis ms we re a fun ction of reagents a nd co nditions. The mo t prcvalent mecha ni sm is presuma bly the di splace me nt of a fluoride anion by another anion, probably via the fo rmation of transition co mplexes of difl'erent lifetimes. Howeve r, simple ionization 0 1' attack by neutral species may occ ur under some co nditions. The diazotization a nd oxidation of pentafluoroan il ine were also inv estigated.

Synthesis of Fluoro-Aromatics by Balz-Schiemann Reaction ?A Greener Approach

“…The detailed examination of the reaction mixture indicates the presence of 2,3,5,6,-tetrafluorophenol, 2,3,4,5,6 pentafluorobenzene and decafluorodiazoamino-benzene as major products [25][26][27] .…”

Pentafluorophenyl alkyl and vinyl ethers

“…The distribution of products seems to indicate that random scissions occur according to eqs 1 and 2. The pyrolysis products were further complicated by competing secondary reactions , which appeared to yield products which were simple addition products of the olefin formed from the initial pyrolysis, as shown in eqs 3 and 4 (or various combinations thereof), (4) This was especially evident in the case of the bromine derivative (table 1, R = Br). The large proportion of I-bromo-l-pentafluorophenoxyethane formed in this pyrolysis would seem to indicate that both types of reaction (eqs 3 and 4) had occurred.…”

“…The pe ntafluoroph e nyl alkyl e th ers were sy nth es ized as precursors to pe ntafluoroph e nyl vinyl etheL In the past, variou s derivatives of fluorinated ani soles [2][3][4] and phenetoles [3 , 5] have been prepared by the nucleo phili c alkoxide attack on hexafluorob e nze ne _ Similarly, we have 'synthesized 2-pentafluorophenoxy-l, l,l-trifluoroethane from hexafluorobenzen e and sodium trifluoroe thoxid e usin g tetrahydrofuran as th e solve nt.…”

“…Since pentafluorophenoxide is considered a weak nucleophile [4,6], the choice of either te trahydrofuran or N,N-dime thylformamide as the solvent for these reactions appears to depend on the relative activity of th e halid e to be replaced_ For example, at 90 °C in N ,N-dimethylformamide, the reaction between pentafluorophenoxide and 1,2-dibromoethane is essentially complete in a few hours , whereas the yield of product on re fluxing in tetrahydrofuran for 18 hr was only 10 percent-…”

Synthesis of poly-p-oxyperfluorobenzylene and related polymers. A novel synthesis of the monomer 2,3,5,6-tetrafluoro-4-trifluoromethylphenol

“…The liquid product was s hown by vapor phase c hromatography (using the two columns me ntion ed previously) to consist of but one substance. Near-infrared analysis of the type reported for similar halophenols [10] appears to suggest either a para or meta orientation of the hydroxyl group with reference to the trifluoromethyl group. Nuclear magnetic resonance analysis confirms the para orientation.…”