Hydrophosphonylation of Alkynes with Trialkyl Phosphites Catalyzed by Nickel

Abstract

The use of simple and inexpensive NiCl2⋅6 H2O as a catalyst precursor for C−P bond formation in the presence of commercially available trialkyl phosphites (P(OR)3, R=Et, iPr, Bu, SiMe3) along with several alkynes is presented. Control experiments showed the in situ formation of (RO)2P(O)H as the species that undergo the addition into the C≡C bond at the alkynes to yield the product of P−H addition. The hydrophosphonylation of diphenylacetylene with P(OEt)3, P(OiPr)3, and P(OSiMe3)3 proceeds in high yields (>92 %) without the need of a specific solvent or ligand. This method is useful for the preparation of organophosphonates for both phenylacetylene as a terminal alkyne model and internal alkynes in yields that range from good to modest.

Taming Brønsted Acid Reactivity: Nucleophilic Substitutions of Propargylic Alcohols with N-Nucleophiles Mediated by Phosphorus-Based Brønsted Acid Catalysts

“…13 Triphenyl and triethyl phosphites were both acceptable catalysts for the model reaction (Table 1, entries 7 and 8), as they generate in situ the corresponding (HO)P(OR) 2 derivatives. Indeed, when triphenylphosphite was heated at 110 °C for 24 h in technical solvent, 11% of hydrolyzed diphenylphosphite was formed together with 2% of oxidized triphenylphosphate; 14 when water was added, all phosphite was converted into phosphonic acid (83%) and triphenylphosphate (17%).…”

Metal-Catalyzed P–C Bond Formation via P–H Oxidative Addition: Fundamentals and Recent Advances

“…In the proposed mechanism, after generation of Pd(0) from Pd acetate and PPh 3 , P−H oxidative addition yields Pd hydride 48. After acrylonitrile insertion to give 49, protonolysis of the Pd−C bond with the secondary phosphine oxide substrate yields propionitrile and a Pd intermediate with two phosphido-oxide ligands (50). Proton transfer with the alkyne regenerates the P−H substrate and yields Pd−alkynyl complex 51, whose reductive elimination forms the product and regenerates the Pd(0) catalyst.…”

“…The proposed mechanism (Scheme 20) was similar to that for palladium, involving P−H oxidative addition, alkyne insertion into the Ni−H bond, and reductive elimination. 50 This approach was also extended to nitriles, where using a Lewis acid additive and an excess of the P(V) reagent resulted in nitrile reduction to the amine and P−C bond formation, which was proposed to occur via the intermediate imine ArCHNH (Scheme 20). 51 Scheme 17.…”

Nickel‐Catalyzed Hydrophosphonylation and Hydrogenation of Aromatic Nitriles Assisted by Lewis Acid

“…However, as far as we know, there are no previous reports of either AP or aminobisphosphonates synthesis from nitriles in the presence of a Ni catalyst precursor even when nickel catalysts have shown great versatility for catalyzing several important transformations . With this respect to this point, our research group has recently reported the synthesis of vinylphosphonates from alkynes by addition of H‐phosphites formed in situ from trialkyl phosphites in the presence of inexpensive nickel chloride (NiCl 2 .6H 2 O) …”

“…In order to further optimize the reaction time (Table , entry 4), we decided to perform the nitrile hydrophosphonylation in a two‐step manner (Table ). The first step was in situ formation of HP(O)(O i Pr) 2 from P(O i Pr) 3 in the presence of NiCl 2 .6H 2 O (Method A) . The HP(O)(O i Pr) 2 was produced with 80 % selectivity and 99 % conversion of triisopropyl‐phosphite after 108 h. Alternatively, hydrolysis of P(O i Pr) 3 was also used to obtain HP(O)(O i Pr) 2 at both 85 % selectivity and full conversion of the phosphite after 18 h (Method B).…”