ChemInform Abstract: SYNTHESIS OF MONO‐ AND BISPHOSPHONIUM SALTS CONTAINING PHENYL AND HETEROCYCLIC NUCLEI IN PHOSPHORUS

Abstract

Bei der Umsetzung der 5‐Brom‐2‐furancarbonsäure (I) mit Triphenylphosphin (II) bei höherer Temperatur tritt Decarboxylierung zum Phosphoniumsalz (III) ein.

Metal-Free Synthesis of Aryltriphenylphosphonium Bromides by the Reaction of Triphenylphosphine with Aryl Bromides in Refluxing Phenol

“…As mentioned above, the reported metal-free synthesis of aryltriphenylphosphonium salts from Ph 3 P and aryl halides requires very high temperature (>260 °C), 16−18 we initially hypothesized that using Ph 2 PCy instead of Ph 3 P would lower the reaction temperature due to the stronger nucleophilicity of Ph 2 PCy than Ph 3 P. 20 To test this hypothesis, we chose 4-bromobiphenyl as a model compound for aryl halides. Screening solvents with a boiling point of around 200 °C revealed that tetraline (bp 207 °C) and PhCN (bp 191 °C) gave phosphonium salt 1 in yields less than 10% but phenol (bp 182 °C) afforded 1 in an excellent yield (92%) (Table 1, entries 1–3).…”

“…As mentioned above, the reported metal-free synthesis of aryltriphenylphosphonium salts from Ph 3 P and aryl halides requires very high temperature (>260 °C), − we initially hypothesized that using Ph 2 PCy instead of Ph 3 P would lower the reaction temperature due to the stronger nucleophilicity of Ph 2 PCy than Ph 3 P . To test this hypothesis, we chose 4-bromobiphenyl as a model compound for aryl halides.…”

“…In the absence of metal, few aryltriphenylphosphonium salts have also been prepared from Ph 3 P and aryl halides but require very high temperature (>260 °C). 16−18 Jugé and co-workers 19 have reported a method based aryne chemistry for the preparation of P-stereogenic tetraarylphosphonium triflates at room temperature, but this method suffers from the use of expensive starting material and poor regioselectivity. Herein, we report a synthesis of aryltriphenylphosphonium bromides from Ph 3 P and aryl bromides (Scheme 1E) not only in the absence of metal but also at around 182 °C, a temperature comparable to that for the nickel-catalyzed method (Scheme 1C).…”

“…Four methods have emerged for the synthesis of aryltriphenylphosphonium salts by the reactions of Ph 3 P with (1) aryl radicals in situ generated by CoCl 2 -catalyzed reaction of Grignard reagents with aryl bromides (Scheme A), (2) diazonium salts (Scheme B), (3) aryl halides catalyzed by nickel (Scheme C), and (4) aryl halides or pseudohalides catalyzed by palladium (Scheme D). − These methods require using either a metal catalyst or unstable, explosive diazonium salts. In the absence of metal, few aryltriphenylphosphonium salts have also been prepared from Ph 3 P and aryl halides but require very high temperature (>260 °C). − Jugé and co-workers have reported a method based aryne chemistry for the preparation of P-stereogenic tetraarylphosphonium triflates at room temperature, but this method suffers from the use of expensive starting material and poor regioselectivity. Herein, we report a synthesis of aryltriphenylphosphonium bromides from Ph 3 P and aryl bromides (Scheme E) not only in the absence of metal but also at around 182 °C, a temperature comparable to that for the nickel-catalyzed method (Scheme C).…”