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A literature survey of the P–C coupling reactions of 1,4-and 1,2-bromo-iodobenzenes with diphenylphosphine oxide or diethyl phosphite under different conditions comprising Pd-, Ni-, or Cu-catalysis revealed that, depending on the experimental details, the yields of the corresponding >P(O)-bromobenzenes were rather diverse and occasionally contradicting. Therefore, the reactivity of a series of 1,4-, 1,3- and 1,2-dibromo- and bromo-iodobenzenes with the above mentioned P-reagents was evaluated under the "P-ligand-free" microwave (MW)-assisted conditions elaborated by us. Starting from dibromobenzenes and iodo-bromoarenes, practical and competent syntheses were developed for phosphonoyl- and phosphinoyl-bromoarenes, and, in a few instances, for arenes with two P-functions. The cheaper dibromobenzenes may be substituted for the bromo-iodo derivatives. In all, 12 products were prepared in yields of 45–82%. They were fully characterized. The method described does not require the use of traditional P-ligands. [ABSTRACT FROM AUTHOR]

A process for the synthesis of P -chiral triarylphosphine sulfides via sequential Pd-catalyzed stereospecific P–C coupling reactions of P -chiral precursors prepared by enzymatic desymmetrization was developed. Three independent aryl substituents could be introduced onto the P atom by the sequential P–C couplings under mild conditions while retaining the high enantiopurity. [ABSTRACT FROM AUTHOR]

Our group introduced a green protocol for the Pd(OAc)2- or NiCl2-catalyzed P–C coupling reaction of aryl halides and various > P(O)H-compounds under MW conditions without directly added P-ligands. The reactivity of a few aryl derivatives in the Pd(OAc)2-catalyzed Hirao reaction was also studied. An induction period was observed in the reaction of bromobenzene and diphenylphosphine oxide. Finally, the less known copper(I)-promoted P–C coupling reactions were investigated experimentally. The mechanism was explored by quantum chemical calculations. [ABSTRACT FROM AUTHOR]

As phosphines readily invert, the synthesis of P-chiral phosphines is a challenging task and has been rarely investigated. We report the synthesis of a nickel complex [Ni-((S,S)Me-FerroLANE)(phenyl)(I)] (Ni-Cat.1) and its performance in a P-C coupling reaction to generate P-chiral phosphine. The Ni-Cat.1 was synthesized by mixing ligand (S,S) Me-FerroLANE with the metal precursor [(diphenylphosphanyl)nickel(phenyl)(I)] in good yield. Ni-Cat.1 was characterized using different spectroscopic and analytical techniques. Treatment of racemic methyl(phenyl)phosphine (1) with 1-(3-iodophenyl)urea (2) produced the corresponding P-chiral supramolecular phosphine (3). Optimization of reaction parameters produced sulfur protected phosphine N-(3-(methyl(phenyl)phosphorothioyl)phenyl)formamide (3’) with excellent enantiomeric excess (99% ee) and moderate conversion (51%). [ABSTRACT FROM AUTHOR]

A literature survey of the P–C coupling reactions of 1,4-and 1,2-bromo-iodobenzenes with diphenylphosphine oxide or diethyl phosphite under different conditions comprising Pd-, Ni-, or Cu-catalysis revealed that, depending on the experimental details, the yields of the corresponding >P(O)-bromobenzenes were rather diverse and occasionally contradicting. Therefore, the reactivity of a series of 1,4-, 1,3- and 1,2-dibromo- and bromo-iodobenzenes with the above mentioned P-reagents was evaluated under the “P-ligand-free” microwave (MW)-assisted conditions elaborated by us. Starting from dibromobenzenes and iodo-bromoarenes, practical and competent syntheses were developed for phosphonoyl- and phosphinoyl-bromoarenes, and, in a few instances, for arenes with two P-functions. The cheaper dibromobenzenes may be substituted for the bromo-iodo derivatives. In all, 12 products were prepared in yields of 45–82%. They were fully characterized. The method described does not require the use of traditional P-ligands.

Our group described a green, “P-ligand-free”, Pd(OAc)2- or NiCl2-catalyzed synthesis under MW conditions. The reactivity of a few aryl derivatives in the Pd(OAc)2-catalyzed, “P-ligand-free” P–C coupling reactions under MW condition was also studied. An induction period was observed. Finally, the less known copper(I)-promoted reactions were investigated experimentally. The mechanism was explored by quantum chemical calculations.

Phosphinic- and phosphonic esters, as well as phosphine oxides can be easily obtained by P–C coupling reactions of aryl- and vinyl halides with dialkyl phosphites, H-phosphinates and secondary phosphine oxides in the presence of mostly Pd catalysts. The use of the microwave (MW) technique allows the realization of the Hirao reaction more efficiently, economically and environmentally-friendly. [ABSTRACT FROM AUTHOR]

Chiral phosphorus ligands play a central role in majority of the asymmetric transformations. However, access to chiral phosphorus ligands is limited due to their challenging synthesis. Reported here is a highly efficient and accelerated catalytic asymmetric synthesis of P‐stereogenic urea containing phosphines leading to a small library of 18 chiral phosphorus compounds. Characteristic two doublets in a 31P NMR spectrum, spectroscopic and analytical evidences authenticated the formation of [Pd‐{(S,S) Me‐FerroLANE}(m‐phenylurea)(I)] complex. Indeed, [Pd‐{(S,S) Me‐FerroLANE}(m‐phenylurea)(I)] was found to catalyze the C‐P coupling reaction and quantitative conversion was observed within 18 hours. Under optimized conditions, iodophenyl urea's (2a–2j) were treated with secondary phosphines (1a–1c) in presence of [Pd‐{(S,S) Me‐FerroLANE}(m‐phenylurea)(I)] to obtain P‐stereogenic urea phosphines 5a–5r. The identity of these urea derived phosphines was unambiguously ascertained using a combination of spectroscopic and analytical methods. The catalyst tolerated various functional groups and yielded corresponding urea containing phosphines with an enantiomeric excess in the range of 15–62 %. Reported here is a highly efficient and accelerated catalytic asymmetric synthesis of P‐stereogenic urea phosphines leading to a small library of 18 P‐chiral phosphorus compounds. The de novo [Pd‐{(S,S) Me‐FerroLANE}(m‐phenylurea)(I)] catalyst tolerated various functional groups and furnished corresponding urea substituted phosphines with an enantiomeric excess of up to 62 %. [ABSTRACT FROM AUTHOR]

The Hirao reaction involving the phosphinoylation or phosphonation of aryl halides by >P(O)H reagents is a P–C bond forming transformation belonging to the recently very hot topic of cross-couplings. The Pd- or Ni-catalyzed variations take place via the usual cycle including oxidative addition, ligand exchange, and reductive elimination. However, according to the literature, the nature of the transition metal catalysts is not unambiguous. In this feature article, the catalysts described for the Pd(OAc)2-promoted cases are summarized, and it is concluded that the “(HOY2P)2Pd(0)” species (Y = aryl, alkoxy) is the real catalyst. In our model, the excess of the >P(O)H reagent served as the P-ligand. During the less studied Ni(II)-catalyzed instances the “(HOY2P)(−OY2P)Ni(II)Cl−” form was found to enter the catalytic cycle. The newest conclusions involving the exact structure of the catalysts, and the mechanism for their formation explored by us were supported by our earlier experimental data and theoretical calculations.

ABSTRACT A series of eight tetraarylphosphonium polyelectrolytes (TPELs) has been successfully synthesized by polymerization of diphenylphosphine and bis(aryl triflate)s. The bis(aryl triflate)s are readily prepared from bisphenols, some of which are commodity feedstocks such as bisphenol A. The polymerization via palladium catalyzed P-C bond formation produces degrees of polymerization up to 65. All polymeric triflates have reasonable thermal stability in the range of 350-450 °C. The stability of the TPELs to alkaline solution is strongly depending on the spacer between adjacent phosphonium sites. Polymers with electron-releasing and bulky substituent para- to the phosphonium site have improved stability while those with electron-withdrawing substituent para- to phosphonium site have decreased alkaline stability due to decomposition via a nucleophilic aromatic substitution pathway. These findings have important ramifications for the design of ionomers for alkaline exchange membrane fuel cells and related electrochemical energy conversion devices. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1984-1990 [ABSTRACT FROM AUTHOR]

• New variation for the Hirao P–C coupling reaction. • Cu(II) salts may be novel precursors for P- and N-complexes. • Excess of the > P (O)H reagent can substitute usual P-ligands via its tautomeric form. • Efficient synthesis of tertiary phosphine oxides and phosphonates. • The mechanism involves a Cu(II) → Cu(I) transition. After surveying the most important results described on the Pd(0)/Pd(II)- and Ni(II)-catalyzed P–C couplings of bromobenzene and diethyl phosphite or diphenylphosphine oxide, the simple Hirao reactions catalyzed by different Cu(II) salts were investigated. In these instances, the more reactive iodobenzene had to be used. CuSO 4 and Cu(OAc) 2 · H 2 O were found suitable catalyst precursors in case they were used together with two equiv. of triethylamine suggesting the role of the amine in the complexation. Theoretical calculations suggested that the corresponding Cu(I) species formed from the initial Cu(II) salt is involved in the catalytic cycle. [Display omitted] [ABSTRACT FROM AUTHOR]

P-C coupling reactions of a variety of >P(O)H species with aryl bromides were found to take place under P-ligand-free microwave conditions. [ABSTRACT FROM PUBLISHER]

Abstract: Under microwave conditions, the P–C coupling of aryl bromides and >P(O)H species, such as dialkyl phosphites, alkyl aryl-H-phosphinates, or diphenylphosphine oxide takes place in the presence of Pd(OAc)2 as the catalyst and triethylamine as the base without using any P-ligand or solvent. The method described is green and is of more general value [Copyright &y& Elsevier]

The Hirao reaction involving the phosphinoylation or phosphonation of aryl halides by >P(O)H reagents is a P–C bond forming transformation belonging to the recently very hot topic of cross-couplings. The Pd- or Ni-catalyzed variations take place via the usual cycle including oxidative addition, ligand exchange, and reductive elimination. However, according to the literature, the nature of the transition metal catalysts is not unambiguous. In this feature article, the catalysts described for the Pd(OAc)2-promoted cases are summarized, and it is concluded that the "(HOY2P)2Pd(0)" species (Y = aryl, alkoxy) is the real catalyst. In our model, the excess of the >P(O)H reagent served as the P-ligand. During the less studied Ni(II)-catalyzed instances the "(HOY2P)(−OY2P)Ni(II)Cl−" form was found to enter the catalytic cycle. The newest conclusions involving the exact structure of the catalysts, and the mechanism for their formation explored by us were supported by our earlier experimental data and theoretical calculations. [ABSTRACT FROM AUTHOR]

Background: The Hirao reaction discovered ca. 35 years ago is an important P-C coupling protocol between dialkyl phosphites and aryl halides in the presence of Pd(PPh3)4 as the catalyst and a base to provide aryl phosphonates. Then, the reaction was extended to other Preagents, such as secondary phosphine oxides and H-phosphinates and to other aryl and hetaryl derivatives to afford also phosphinic esters and tertiary phosphine oxides. Instead of the Pd(PPh3)4 catalyst, Pd(OAc)2 and Ni-salts were also applied as catalyst precursors together with a number of mono- and bidentate P-ligands., Objective: In our review, we undertook to summarize the target reaction with a special stress on the developments attained in the last 6 years, hence this paper is an update of our earlier reviews in a similar topic., Conclusions: "Greener" syntheses aimed at utilizing phase transfer catalytic and microwave-assisted approaches, even under "P-ligand-free. or even solvent-free conditions are the up-to date versions of the classical Hirao reaction. The mechanism of the reaction is also in the focus these days., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)