Errocene ligands are compared with these of their R,Sp,Rp-configured diastereomers and these on the corresponding Walphos ligands.Outcomes AND DISCUSSION Synthesis of Ligands and Complexes. Ligands (R,Sp,Sp)1 and (R,Sp,Sp)-2 have been ready inside a way analogous to that for their R,Sp,Rp-configured diastereomers. Nonetheless, racemicReceived: November five, 2013 Published: April 9,dx.doi.org/10.1021/om401074a | Organometallics 2014, 33, 1945-Organometallics Scheme 1. Synthesis of Ligands (R,Sp,Sp)-1 and (R,Sp,Sp)-ArticleFigure 1. Structural features of (R,Sp,Sp)-6, (R,Sp,Sp)-7, and (R,Sp,Sp)-2?BH3.2-bromoiodoferrocene (rac-4) was utilized as opposed to (R)-2bromoiodoferrocene ((R)-4). A Negishi coupling4 of (R)-1(N,N-dimethylamino)ethylferrocene with rac-45 gave both diastereomers of five with an general yield of 77 ((R,Sp,Rp)-5, 45 ; (R,Sp,Sp)-5, 32 ). The two diastereomers could be separated by chromatography, plus the diastereomer (R,Sp,Sp)56 was reacted with n-BuLi and subsequently quenched with chlorodiphenylphosphine. Oxidation on the resulting aminophosphine (R,Sp,Sp)-6 with H2O2 resulted in the formation on the phosphine oxide (R,Sp,Sp)-7 (52 based on 5), which may also be obtained directly from 5. Reaction of (R,Sp,Sp)-5 with n-BuLi followed by remedy with diphenylphosphinyl chloride gave the phosphine oxide (R,Sp,Sp)-7 in 77 yield. X-ray diffraction research around the aminophosphine (R,Sp,Sp)-6 as well as the aminophosphine oxide (R,Sp,Sp)-7 confirmed their structural integrity also as their absolute configurations (Figure 1; for the crystallographic information see the Experimental Section). Further reaction of phosphine oxide 7 with bis[3,5-bis(trifluoromethyl)phenyl]phosphine or diphenylphosphine in acetic acid at 70 gave the phosphine-phosphine oxides (R,Sp,Sp)-8 (60 ) and (R,Sp,Sp)-9.1b In remedy the side-chain phosphorus of (R,Sp,Sp)-9 was found to become rather sensitive to oxidation plus the crude item 9 was thus used within the last step. Reduction of phosphine oxides eight and 9 with polymethylhydrosiloxane/titanium isopropoxide7 gave the preferred ligands (R,Sp,Sp)-1 (92 ) and (R,Sp,Sp)-2 (70 depending on 7). A compact amount of (R,Sp,Sp)-2 was then reacted with BH3 HF to offer the bis(borane) complex (R,Sp,Sp)-2?BH3 (99 ). The molecular structure of this compound was determined by X-ray diffraction (Figure 1 and Experimental Section). Also, ligand (R,Sp,Sp)-2 was reacted with [PdCl2(CH3CN)2] to give the palladium dichloride complicated [PdCl2((R,Sp,Sp)-2)] in 99 yield.Within the complex (R,Sp,Sp)-2?BH3, also as in precursors six and 7 (Figure 1), the two ferrocene units adopt an anti arrangement with Fe1-C1-C11-Fe2 dihedral angles of -178.5 and -177.three?(six), 176.eight?(7), and 150.8?(two?BH3). In this conformation the diphenylphosphino units of 2 are oriented trans to every single other (torsion angles C2-C1-C11-C12 of 178.2-(2-Bromo-4-hydroxyphenyl)acetic acid manufacturer 0 and 180.2369772-11-0 site 0?(six), 178.PMID:36717102 four?(7), and 158.four?(2?BH3). The ligand (R,Sp,Sp)-2 will not be incredibly effectively preoriented for cis coordination, however it could quickly be transformed in to the palladium dichloride complicated [PdCl2((R,Sp,Sp)-2)]. Asymmetric Hydrogenations. Each on the newly synthesized Walphos analogues 1 and two with an R,Sp,Sp absolute configuration had been tested as ligands within the asymmetric hydrogenation of numerous alkenes and two ketones (Chart 2). All catalysts for the hydrogenation of alkenes have been formed in situ by reacting the ligands with the metal precursor [Rh(NBD)2]BF4 (NBD = norbornadiene). The catalysts for the hydrogenation of ketones were prepared by reac.
