Bis(1,1‐dimethylethyl)[2′,4′,6′‐tris‐(1‐methylethyl)[1,1′‐biphenyl]‐2‐yl]‐phosphine and Dicyclohexyl[2′,4′,6′‐tris(1‐methylethyl)[1,1′‐biphenyl]‐2‐yl]phosphine

Abstract

X-Phos[564483-18-7] C33H49P (MW 476.72) InChI = 1S/C33H49P/c1-23(2)26-21-30(24(3)4)33(31(22-26)25(5)6)29-19-13-14-20-32(29)34(27-15-9-7-10-16-27)28-17-11-8-12-18-28/h13-14,19-25,27-28H,7-12,15-18H2,1-6H3 InChIKey = UGOMMVLRQDMAQQ-UHFFFAOYSA-N (bulky, electron-rich monophosphine used as ligand in transition-metal catalyzed reactions, especially in the context of Pd chemistry) Alternate Names:  2-dicyclohexylphosphino-2′,4′,6′-triisopropyl biphenyl, X-Phos. Physical Data: mp 187–190°C. Solubility: soluble in most organic solvents. Form Supplied in: white solid; widely available. t-BuX-Phos [564483-19-8] C29H45P (MW 424.65) InChI = 1S/C29H45P/c1-19(2)22-17-24(20(3)4)27(25(18-22)21(5)6)23-15-13-14-16-26(23)30(28(7,8)9)29(10,11)12/h13-21H,1-12H3 InChIKey = SACNIGZYDTUHKB-UHFFFAOYSA-N (bulky, electron-rich monophosphine used as ligand in Pd-catalyzed reactions) Alternate Names: 2-di-tert-butylphosphino-2′,4′,6′-triisopropyl biphenyl, tert-BuX-Phos, di-tert-BuXPhos. Physical Data: mp 148–151 °C. Solubility: soluble in most organic solvents. Form Supplied in: white solid; widely available. Handling, Storage, and Precautions: the oxidation of these and related phosphines has been examined.1 The presence of three isopropyl groups on the 2′,4′, and 6′ positions of the nonphosphine-containing ring reduces their reactivity toward atmospheric oxygen to less than 3% at room temperature in toluene solution after 65 h. Under an atmosphere of O2 at 100 °C for 65 h only 28% and 13% phosphine oxide is formed from X-Phos and tert-BuX-Phos, respectively. Preparative Method: X-Phos can be prepared by reaction of 2-bromochlorobenzene with the Grignard reagent from 1-bromo-2,4,6-triisopropylbenzene in THF, followed by addition of catalytic CuCl and ClPCy2. A similar procedure using ClPtertBu2 was applied for the synthesis of tert-BuX-Phos.2