ABSTRACT
Homogenous catalysis is an essential tool within the commercial manufacture of bulk and fine chemicals. Within this, phosphine ligands, such as tricyclohexylphosphine, otherwise known as CYTOP® 366, are a crucial component. When designing a pathway to your ligand of choice, some key considerations include safety, yield and quality, but at commercial volumes we must also balance cost and consider the technologies readily available. Herein, we report the synthetic route that was chosen to manufacture tricyclohexylphosphine at commercial scale. We also consider, with the use of computational calculations, why traditional hydrophosphination methods failed, where the selected pathway succeeded.
ABSTRACT
Tris(3-hydroxypropyl)phosphine (THPP) is demonstrated to be a versatile, water-soluble and air-stable reducing agent, allowing for the rapid, irreversible reductive cleavage of disulfide bonds in both aqueous and buffered aqueous-organic media. The reagent shows exceptional stability at biological pH under which condition it permits the rapid reduction of a wide range of differentially functionalized small-molecule disulfides.
Subject(s)
Air , Disulfides/chemistry , Phosphines/chemistry , Hydrogen-Ion Concentration , Indicators and Reagents/chemistry , Molecular Structure , Oxidation-Reduction/drug effects , Phosphines/pharmacologyABSTRACT
The synthesis of a series of [(IPr)Pd(R-acac)Cl] precatalysts (acac=acetylacetonato; IPr=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), where the acac ligand on palladium has been systematically modified through terminal substitution, is reported. The following substituted acac ligands are employed in this study: dibenzoylmethanato (dbm), benzoylacetonato (bac), tetramethylheptanedionato (tmhd), and hexafluoroacetylacetonato (hfac). Full spectroscopic characterization of the new complexes is provided along with X-ray studies for three of these. Investigation of their catalytic activity in cross-coupling is also presented through a comparative study in an aryl amination reaction. The catalytic results show a strong correlation between the increased steric bulk of the acac substituents and an increased activation rate of the precatalyst, going from the acac to the tmhd ligand. This observation, along with the inertness of the hfac compound, seems to support our previous proposal for the activation mechanism of these complexes under cross-coupling conditions.
Subject(s)
Coordination Complexes/chemistry , Palladium/chemistry , Amination , Catalysis , Coordination Complexes/chemical synthesis , Crystallography, X-Ray , Heterocyclic Compounds/chemistry , Ligands , Molecular ConformationABSTRACT
Protic aminophosphines with multiple chiral centers were synthesized in good yields and high purity by the nucleophilic ring-opening of N-protected cyclic sulfamidates with metal phosphides, followed by hydrolysis and deprotection. This synthetic approach is clean, scalable, and high yielding. The method provides an efficient alternative route for the synthesis of chiral aminophosphines.
ABSTRACT
The aminophosphine ligands R(2)P(CH(2))(2)NH(2) and R(2)P(CH(2))(3)NH(2) (R = Ph, (i)Pr, (t)Bu) were isolated in good to excellent yields from the reaction of LiPR(2) with Cl(CH(2))(2)N(TMS)(2) and Cl(CH(2))(3)N(TMS)(2), respectively, followed by hydrolysis. This approach allows fine tuning of the ligands' stereoelectronic properties through the variation of the substituents on the phosphine. The aminophosphine ligands were used to prepare the ruthenium complexes RuCl(2)(R(2)P(CH(2))(2)NH(2))(2) and RuCl(2)(R(2)P(CH(2))(3)NH(2))(2) by reacting a 2:1 mixture of the respective ligand and [RuCl(2)(cod)](n) in an appropriate solvent. The resulting complexes were found to be excellent catalysts for the hydrogenation of ketones and imines.
ABSTRACT
A very straightforward synthesis of (IPr)Pd(acac)Cl from two commercially available starting materials, Pd(acac)2 and IPr.HCl [acac = acetylacetonate; IPr = N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene], has been developed. The resulting complex, (IPr)Pd(acac)Cl (1), has proven to be a highly active PdII precatalyst in the Buchwald-Hartwig and the alpha-ketone arylation reactions. A wide range of substrates has been screened, including unactivated, sterically hindered, and heterocyclic aryl chlorides.
