An Improved Synthesis of BrettPhos‐ and RockPhos‐Type Biarylphosphine Ligands

Abstract

Improved processes for the preparation of biphenyl-based phosphine ligands t-BuBrettPhos, RockPhos, and BrettPhos are presented. The new methods, featuring the use of Grignard reagents and catalytic amounts of copper, are superior to the previous methods, which require the use of t-butyllithium and stoichiometric amounts of copper. Specifically, the use of less dangerous reagents provides a safer process, while the use of catalytic amounts of copper allows for the isolation of pure products in high yield. These improvements are particularly significant for the large scale preparation of these ligands.

Synthesis, Structure and Nickel Carbonyl Complexes of Dialkylterphenyl Phosphines

“…Before discussing pertinent characterization data, trends in isolatedy ields deserve some brief comments. All phosphines but L16 and L9 can be produced on gramscale runs in 50-60 %y ields, hence comparable to those given originally for dialkylbiaryl analogues [37] andf or the recently prepared PMe 2 Ar' (Methyl-JohnPhos;c a. 52 %t hree-step overall yield).…”

“…Our recent synthesis of terphenyl phosphines, PR 2 Ar', [28] followed as lightly modified earlier procedure [23a] and consistedi n the stepwiser eaction of at erphenyl Grignardr eagent, Mg(Ar')X, with PCl 3 ,f ollowed by alkylation using, once more, the appropriate magnesium agent, Mg(R)Br,a ss hown in Scheme 1a.W hereas this method yields satisfactory resultsf or linear hydrocarbyl Rg roupsa nd it was thus applicable to the synthesis of the new phosphines L1 and L2,a ttempts to extend it to the branched or cyclic isopropyl, c-pentyl and chexyl phosphines led either to unreacted starting materials or to complex mixtures of products that could not be characterized (Scheme 1b). Emulating the synthesis of biaryl phophines, [37] the alkylation of PX 2 Ar' was effected in the presence of CuCl. After careful monitoring of reactionc onditions (temperature, concentration of reagents and coppers alt), best results were obtained performing the reaction at room temperature and using PX 2 Ar':Mg(R)Br molar ratios of ca.…”

Stannylation of Aryl Halides, Stille Cross‐Coupling, and One‐Pot, Two‐Step Stannylation/Stille Cross‐Coupling Reactions under Solvent‐Free Conditions

“…of Sn 2 Bu 6 at 110 °C. Various palladium catalysts were tested: (SIPr)Pd(cinn)Cl, the well‐defined expanded ring NHC complex (THP‐Dipp)Pd(cinn)Cl recently developed in our group, the catalytic systems Pd(OAc) 2 /( t Bu) 3 P · HBF 4 and Pd(dba) 2 /( t Bu) 3 P · HBF 4 , Pd(OAc) 2 /SPhos, Pd(OAc) 2 / t BuXPhos, Pd(OAc) 2 /RuPhos, Pd(OAc) 2 /DavePhos, Pd(OAc) 2 / t BuDavePhos, Pd(OAc) 2 / t BuBrettPhos, Pd(OAc) 2 /XantPhos, Pd(OAc) 2 /P( o ‐Tol) 3 , Pd(OAc) 2 /DiPhos, Pd(OAc) 2 /PCy 3 ,[1b] t Bu‐Indenyl(PCy 3 )PdCl, t Bu‐Indenyl(IPr)PdCl, as well as conventional palladium sources Pd(PPh 3 ) 2 Cl 2 , Pd(OAc) 2 /dppf, and Pd(OAc) 2 /DPEPhos (Figure ). Results of the catalytic tests are summarized in Table , Table , and Table .…”

Structure and reactivity of [(L·Pd) n ·(1,5-cyclooctadiene)] ( n = 1–2) complexes bearing biaryl phosphine ligands

“…CD 2 Cl 2 , CDCl 3 , and toluene-d 8 were purchased from Cambridge Isotopes in sealed ampules and used without further purification. Preparations of AdBrettPhos ( 1 ) [7], t BuBrettPhos ( 6 ) [8], RockPhos ( 7 ) [8], 2 [1], 5 [9], 12 [10], 13 [9], 14 [10], and 17 [11] have been previously described. The t BuXPhos ( 8 ) used in this work was purchased from Sigma Aldrich.…”