Enantioselective Hydrophosphination of Enones with

Mar 28, 2014 - ... Schafer , C. P. Owens , C. J. Herting , A. Varela-Alvarez , S. Chen , Z. Niemeyer , D. G. Musaev , M. S. Sigman , H. M. L. Davies ,...
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Enantioselective Hydrophosphination of Enones with Diphenylphosphine Catalyzed by Bis(imidazoline) NCN Pincer Palladium(II) Complexes Xin-Qi Hao, Yong-Wei Zhao, Jing-Jing Yang, Jun-Long Niu, Jun-Fang Gong,* and Mao-Ping Song* College of Chemistry and Molecular Engineering, Henan Key Laboratory of Chemical Biology and Organic Chemistry, Zhengzhou University, Zhengzhou 450001, People’s Republic of China S Supporting Information *

ABSTRACT: A series of chiral NCN pincer Pd(II) complexes with 1,3-bis(2′-imidazolinyl)phenyl (Phebim) ligands were synthesized via the C−H activation or oxidative addition method. A dinuclear macrocyclic Pd(II) complex was also prepared by reaction of the Phebim-H ligand with PdCl2. All of the new compounds were fully characterized, and X-ray singlecrystal structures were obtained for two of the complexes. The Pd(II) complexes were successfully applied to enantioselective hydrophosphination of various enones with diphenylphosphine, providing optically active phosphine derivatives in good yields with enantioselectivities of up to 94% ee.

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INTRODUCTION Organometallic pincer palladium(II) complexes have found wide applications in catalytic organic transformations such as stannylation of allylic or propargylic substrates, allylation of aldehydes or imines, Michael additions, aldol reactions, and particularly a variety of cross-coupling reactions.1 Most of the previous reports have focused on achiral Pd(II) pincers. In contrast, chiral pincers and their use in asymmetric catalysis have not been explored extensively. In addition, the reported enantioselectivities of the catalysis products are often found to be relatively low.1h For example, the NCN pincer metal complexes with tridentate bis(oxazolinyl)phenyl (Phebox) ligands (M = Pd, Pt, Ru, Rh, Ir, etc.) constitute a large family of chiral pincer complexes.2 The Rh− and Ru−Phebox complexes exhibited high efficiency and selectivity in many catalytic reactions such as conjugate reduction, borylation, hydrogenation, transfer hydrogenation, and several carbon− carbon bond formation reactions. However, to our knowledge the Pd−Phebox complexes have only been applied up to now to asymmetric reactions of 2-cyanocarboxylates with Michael acceptors, aldol reactions of isocyanides and aldehydes, and Suzuki−Miyaura couplings. The enantioselectivities obtained were moderate in all cases (up to 34%, 57% ,and 49% ee, respectively).3 Encouragingly, some highly stereoselective reactions catalyzed by pincer Pd complexes have emerged very recently. Among them, Duan and coauthors developed a bis(phosphine) PCP pincer Pd(II) catalyst bearing stereogenic benzylic methylene centers for the asymmetric addition of R2PH to N-tosylimines4 and some activated alkenes including enones,5a enals,5b nitroalkenes,5c α,β-unsaturated N-acylpyrroles,5d and carboxylic and sulfonic esters.5e−g Nakamura and coworkers applied bis(imidazoline) NCN pincer Pd(II) complexes to the reaction of benzyl nitriles with imines, aza-MBH © 2014 American Chemical Society

reactions of acrylonitrile with imines, decarboxylative Mannichtype reactions of cyanoacetic acids with imines, and allylations of ketimines.6 All of these reactions could provide excellent stereocontrol (≥90% ee). Furthermore, it was found that bis(imidazolidine) NCN pincer Pd(II) complexes showed high levels of enantioselectivities in the reaction of nitroalkenes with malononitriles (up to 93% ee).7 In 2006, we reported the first synthesis of the chiral 1,3-bis(2′-imidazolinyl)benzene (Phebim-H) ligands, which are structural analogues of Phebox-H ligands, as well as the corresponding NCN pincer Pt(II) complexes via C−H activation of the ligands.8 Then the Pd−, Ni−, and Rh−Phebim complexes were prepared successively via a similar C−H activation procedure, and some of them showed promising stereoselectivities in asymmetric catalysis.9 In particular, a preliminary survey on the catalysis of Pd− Phebim complexes was carried out. The two complexes A and B (Chart 1) were examined as the catalysts for enantioselective hydrophosphination of chalcone with diphenylphosphine (1,4conjugate addition of Ph2P to chalcone). Complex A, having a (4S)-phenyl substituent, could give the expected adduct in 84% yield with 85% ee.10 Although the catalytic results are fairly Chart 1

Received: February 7, 2014 Published: March 28, 2014 1801

dx.doi.org/10.1021/om500144b | Organometallics 2014, 33, 1801−1811

Organometallics

Article

Scheme 1. Synthesis of Chiral Bis(imidazoline) NCN Pincer Pd(II) Chloride Complexes 2a−c via C−H Activation

Scheme 2. Synthesis of Chiral Dinuclear Macrocyclic Pd(II) Complex 3

palladated products and improve the efficiency of the expected C2-palladation. The 5-nitro group was introduced to tune the electronic effect of the ensuing Pd complex and to optimize the catalyst. Thus, ligands 1a−c were synthesized starting from commercially available 5-tert-butyl- or 5-nitroisophthalic acid according to the procedure previously reported by us (the synthetic route is given in Scheme S1 in the Supporting Information).8,9a The following palladation reaction was carried out by using Pd(OAc)2 as the metal(II) source under the conditions similar to those used before.9a It was found that complex 2a with a (4S)-phenyl substituent was obtained in 13% yield, which was only slightly improved in comparison with complex A (8% yield) without a tert-butyl group on the central aryl. Pleasingly, complex 2b with (4S,5S)-diphenyl substituents was isolated in good yield (75%). However, it was somewhat confusing that the yield of complex 2c also with (4S,5S)diphenyl substituents was rather low (15%), considering that several related complexes with or without the nitro group could be produced in 31−54% yields.9a,10 We then tried the reaction of ligand 1c with PdCl2 in the presence of Et3N in refluxing toluene; the expected Pd pincer was not obtained, and the dinuclear macrocyclic Pd(II) complex 3 was isolated instead in high yield this time (85%, Scheme 2). The result indicated that Pd(OAc)2 was more effective than PdCl2 in the central aryl Cpalladation of the Phebim-H ligands. Overall, the yields of the Pd-Phebim complexes via C−H activation were not very high, which was unfavorable to their use in catalytic applications. We therefore sought the oxidative addition method to get these complexes. For this purpose, the 2-bromo-1,3-bis(imidazoline)benzene ligands 4 were required. The preparation of the ligands can be easily done starting from 2-bromo-m-xylene (the synthetic route is given in Scheme S2 in the Supporting Information). Oxidation of 2-bromo-m-xylene by KMnO4 produced 2-bromoisophthalic acid followed by treatment with SOCl2 to afford 2-bromoisophthalic chloride according to the published procedure.13 Reaction of the chloride with various chiral amino alcohols, including Lphenylglycinol, L-valinol, L-tert-leucinol, and (1R,2S)-2-amino1,2-diphenylethanol, gave the known 2-bromo-1,3-bis(amido

good, the synthetic yield of this Pd(II) complex via C−H activation was rather low ( 240 °C. [α]D20 = +97° (c 0.260, CH2Cl2). 1 H NMR (400 MHz, CDCl3): δ 7.51 (d, J = 7.6 Hz, 3H, PhH), 7.33 (t, J = 7.2 Hz, 4H, PhH), 7.26−7.22 (m, 7H, PhH and NArH), 7.18 (d, J = 8.4 Hz, 4H, NArH), 6.38 (s, 2H, ArH), 5.38 (dd, J = 4.4, 10.8 Hz, 1806

dx.doi.org/10.1021/om500144b | Organometallics 2014, 33, 1801−1811

Organometallics

Article

δ 7.51 (d, J = 7.6 Hz, 2H, ArH), 7.44 (d, J = 7.5 Hz, 4H, ArH), 7.39− 7.33 (m, 5H, ArH), 7.28−7.26 (m, 2H, ArH), 6.89 (d, J = 8.3 Hz, 4H, NArH), 6.59 (d, J = 8.3 Hz, 4H, NArH), 5.34 (app t, J = 10.2 Hz, 2H, NCH), 4.35 (app t, J = 10.2 Hz, 2H, NCH2), 3.93 (app t, J = 9.3 Hz, 2H, NCH2), 2.23 (s, 6H, CH3). 13C NMR (100 MHz, CDCl3): δ 160.7, 143.6, 138.0, 135.1, 132.7, 131.8, 129.5, 128.5, 127.5, 127.2, 126.9, 122.0, 120.3, 67.6, 59.7, 20.7. HRMS (positive ESI): [M + H]+ calcd for C38H34BrN4 625.1967, found 625.1965. 2-Bromo-1,3-bis((S)-4-isopropyl-1-p-tolyl-4,5-dihydro-1H-imidazol-2-yl)benzene (4b). Yellow solid (390.2 mg, 70%). Mp: 60−62 °C. [α]D20 = −98° (c 0.326, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 7.41 (d, J = 7.5 Hz, 2H, ArH), 7.30 (t, J = 7.6 Hz, 1H, ArH), 6.88 (d, J = 8.2 Hz, 4H, NArH), 6.55 (d, J = 8.4 Hz, 4H, NArH), 4.08−4.02 (m, 2H, NCH), 3.95 (app t, J = 9.2 Hz, 2H, NCH2), 3.69 (app t, J = 8.6 Hz, 2H, NCH2), 2.23 (s, 6H, CH3), 1.97−1.93 (m, 2H, (CH3)2CH), 1.03 (d, J = 6.8 Hz, 6H, (CH3)2CH), 0.98 (d, J = 6.8 Hz, 6H, (CH3)2CH). 13C NMR (100 MHz, CDCl3): δ 159.5, 138.4, 135.4, 132.2, 131.6, 129.4, 127.4, 121.9, 120.1, 70.0, 54.0, 32.9, 20.7, 19.0, 18.1. HRMS (positive ESI): [M + H]+ calcd for C32H38BrN4 557.2280, found 557.2278. 2-Bromo-1,3-bis((S)-4-tert-butyl-1-p-tolyl-4,5-dihydro-1H-imidazol-2-yl)benzene (4c). Pale yellow solid (351.4 mg, 60%). Mp: 87−88 °C. [α]D20 = −74° (c 0.287, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 7.46−7.41 (m, 2H, ArH), 7.30 (t, J = 7.6 Hz, 1H, ArH), 6.87 (d, J = 8.2 Hz, 4H, NArH), 6.56 (d, J = 8.4 Hz, 4H, NArH), 3.97 (app t, J = 10.7 Hz, 2H, NCH), 3.91 (app t, J = 8.9 Hz, 2H, NCH2), 3.74 (app t, J = 8.6 Hz, 2H, NCH2), 2.24 (s, 6H, CH3), 0.99 (s, 18H, C(CH3)3). 13C NMR (100 MHz, CDCl3): δ 159.5, 138.5, 135.6, 132.0, 131.6, 129.4, 127.4, 120.3, 120.1, 73.9, 52.9, 34.3, 26.1, 20.7. HRMS (positive ESI): [M + H]+ calcd for C34H42BrN4 585.2593, found 585.2596. 2-Bromo-1,3-bis((S,S)-1-p-tolyl-4,5-diphenyl-4,5-dihydro-1H-imidazol-2-yl)benzene (4d). Pale yellow solid (350.1 mg, 45%). Mp: 115−117 °C. [α]D20 = −35° (c 0.321, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 7.54 (d, J = 6.8 Hz, 2H, ArH), 7.40−7.27 (m, 21H, ArH), 6.77 (d, J = 8.2 Hz, 4H, NArH), 6.63 (d, J = 7.8 Hz, 4H, NArH), 5.21 (d, J = 8.9 Hz, 2H, NCH), 5.00 (d, J = 8.9 Hz, 2H, NCH), 2.12 (s, 6H, CH3). 13C NMR (100 MHz, CDCl3): δ 161.9, 143.3, 141.9, 137.8, 135.1, 134.2, 132.1, 129.5, 128.9, 128.6, 127.8, 127.4, 127.3, 127.0, 123.6, 79.0, 77.3, 20.8. HRMS (positive ESI): [M + H]+ calcd for C50H42BrN4 777.2593, found 777.2596. 2,6-Bis((S)-4-phenyl-1-p-tolyl-4,5-dihydro-1H-imidazol-2-yl)phenylpalladium(II) Bromide (5a). Yellow solid (123.0 mg, 56%). Mp: >290 °C. [α]D20 = +70° (c 0.098, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 7.39 (d, J = 7.3 Hz, 4H, PhH), 7.25 (t, J = 7.3 Hz, 4H, PhH), 7.18−7.13 (m, 6H, PhH and NArH), 7.07 (d, J = 8.2 Hz, 4H, NArH), 6.54 (t, J = 7.9 Hz, 1H, ArH), 6.36 (d, J = 7.8 Hz, 2H, ArH), 5.36 (dd, J = 3.9, 10.7 Hz, 2H, NCH), 4.34 (app t, J = 10.1 Hz, 2H, NCH2), 3.93 (dd, J = 4.0, 9.8 Hz, 2H, NCH2), 2.32 (s, 6H, CH3). 13C NMR (100 MHz, CDCl3): δ 174.8, 170.0, 142.9, 138.1, 137.0, 133.1, 130.4, 128.6, 127.5, 127.1, 126.9, 126.4, 122.0, 65.0, 63.7, 21.2. Anal. Calcd for C38H33BrN4Pd·0.5C6H14-n: C, 63.53; H, 5.20; N, 7.23. Found: C, 63.85; H, 5.25; N, 6.67. 2,6-Bis((S)-4-isopropyl-1-p-tolyl-4,5-dihydro-1H-imidazol-2-yl)phenylpalladium(II) Bromide (5b). Yellow solid (101.6 mg, 51%). Mp: >290 °C. [α]D20 = +140° (c 0.116, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 7.22 (d, J = 8.1 Hz, 4H, NArH), 7.11 (d, J = 8.2 Hz, 4H, NArH), 6.54 (t, J = 7.8 Hz, 1H, ArH), 6.34 (d, J = 7.8 Hz, 2H, ArH), 4.40−4.35 (m, 2H, NCH), 4.01 (app t, J = 10.1 Hz, 2H, NCH2), 3.84 (dd, J = 5.0, 9.9 Hz, 2H, NCH2), 2.98−2.90 (m, 2H, (CH3)2CH), 2.40 (s, 6H, CH3), 0.93 (d, J = 7.0 Hz, 6H, (CH3)2CH), 0.88 (d, J = 6.8 Hz, 6H, (CH3)2CH). 13C NMR (100 MHz, CDCl3): δ 173.4, 168.7, 137.7, 137.3, 133.1, 130.2, 126.7, 126.1, 121.9, 66.8, 54.8, 30.3, 21.2, 18.7, 14.3. Anal. Calcd for C32H37BrN4Pd·0.5CH2Cl2: C, 55.25; H, 5.42; N, 7.93. Found: C, 55.53; H, 5.47; N, 7.69. 2,6-Bis((S)-4-tert-butyl-1-p-tolyl-4,5-dihydro-1H-imidazol-2-yl)phenylpalladium(II) Bromide (5c). Yellow solid (103.8 mg, 50%). Mp: 199−201 °C. [α]D20 = +361° (c 0.098, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 7.21 (d, J = 8.1 Hz, 4H, NArH), 7.13 (d, J = 8.2 Hz, 4H, NArH), 6.54 (t, J = 7.8 Hz, 1H, ArH), 6.35 (d, J = 7.8 Hz, 2H, ArH), 4.16−4.13 (m, 2H, NCH), 4.07 (app t, J = 9.8 Hz, 2H, NCH2),

2H, NCH), 4.43 (app t, J = 10.0 Hz, 2H, NCH2), 4.05 (dd, J = 4.4, 9.8 Hz, 2H, NCH2), 2.39 (s, 6H, CH3), 0.79 (s, 9H, C(CH3)3). 13C NMR (100 MHz, CDCl3): δ 170.9, 169.9, 144.9, 142.7, 138.1, 137.1, 132.5, 130.1, 128.5, 127.5, 127.0, 126.7, 124.6, 64.6, 63.2, 34.4, 30.7, 21.1. Anal. Calcd for C42H41ClN4Pd: C, 67.83; H, 5.56; N, 7.53. Found: C, 67.70; H, 6.38; N, 6.50. 4-tert-Butyl-2,6-bis((S,S)-1-p-tolyl-4,5-diphenyl-4,5-dihydro-1Himidazol-2-yl)phenylpalladium(II) Chloride (2b). Yellow solid (134.4 mg, 0.15 mmol, 75%). Mp: 220−223 °C. [α]D20 = +94° (c 0.116, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 7.41 (d, J = 7.3 Hz, 4H, ArH), 7.35−7.31 (m, 14H, ArH), 7.26−7.22 (m, 3H, ArH), 7.10 (br s, 7H, ArH), 6.36 (s, 2H, ArH), 5.29 (d, J = 5.7 Hz, 2H, NCH), 4.88 (d, J = 5.7 Hz, 2H, NCH), 2.31 (s, 6H, CH3), 0.79 (s, 9H, C(CH3)3). 13C NMR (100 MHz, CDCl3): δ 171.3, 169.4, 145.1, 142.7, 140.3, 138.4, 136.2, 132.8, 129.9, 129.1, 128.7, 128.6, 127.6, 127.4, 126.9, 124.7, 79.2, 74.8, 34.5, 30.7, 21.1. Anal. Calcd for C54H49ClN4Pd· 0.75CH2Cl2: C, 68.53; H, 5.30; N, 5.84. Found: C, 68.52; H, 5.39; N, 5.67. 4-Nitro-2,6-bis((S,S)-1-p-tolyl-4,5-diphenyl-4,5-dihydro-1H-imidazol-2-yl)phenylpalladium(II) Chloride (2c). Yellow solid (26.6 mg, 0.03 mmol, 15%). Mp: 218−219 °C. [α]D20 = +39° (c 0.114, CH2Cl2). 1 H NMR (400 MHz, CDCl3): δ 7.39−7.25 (m, 24H, ArH), 7.15 (br s, 6H, ArH), 5.34 (d, J = 6.0 Hz, 2H, NCH), 4.94 (d, J = 6.0 Hz, 2H, NCH), 2.35 (s, 6H, CH3). 13C NMR (100 MHz, CDCl3): δ 183.3, 168.1, 143.4, 142.0, 139.6, 139.2, 135.1, 133.6, 130.5, 129.2, 128.9, 128.8, 128.0, 127.3, 126.9, 122.0, 79.4, 74.9, 21.2. Anal. Calcd for C50H40ClN5O2Pd: C, 67.88; H, 4.56; N, 7.92. Found: C, 67.56; H, 4.84; N, 7.44. Synthesis of the Dinuclear Palladium Complex 3. A mixture of 1c (74.4 mg, 0.1 mmol) and PdCl2 (17.7 mg, 0.1 mmol) in toluene (15 mL) was refluxed in the presence of Et3N (13.9 μL, 0.1 mmol) for 48 h under a nitrogen atmosphere. After the mixture was cooled and concentrated in vacuo, the residue was purified by preparative TLC on silica gel plates with CH2Cl2 as eluent to afford complex 3 as a yellow solid (78.3 mg, 85%). Mp: 267−269 °C. [α]D20 = +494° (c 0.108, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 10.47 (t, J = 1.8 Hz, 2H, ArH), 9.07 (t, J = 1.5 Hz, 2H, ArH), 7.85 (t, J = 1.7 Hz, 2H, ArH), 7.67 (d, J = 7.2 Hz, 4H, PhH), 7.48 (t, J = 7.2 Hz, 4H, PhH), 7.40− 7.30 (m, 28H, PhH), 7.23 (dd, J = 2.0, 7.8 Hz, 4H, PhH), 7.00 (d, J = 8.2 Hz, 4H, NArH), 6.77 (d, J = 8.3 Hz, 4H, NArH), 6.52 (d, J = 8.2 Hz, 4H, NArH), 5.67 (d, J = 8.2 Hz, 4H, NArH), 5.49 (d, J = 7.0 Hz, 2H, NCH), 5.35 (d, J = 8.7 Hz, 2H, NCH), 4.50 (d, J = 7.0 Hz, 2H, NCH), 4.30 (d, J = 8.8 Hz, 2H, NCH), 2.22 (s, 6H, CH3), 2.08 (s, 6H, CH3). 13C NMR (100 MHz, CDCl3): δ 164.0, 162.1, 146.9, 141.4, 140.8, 140.7, 140.5, 139.2, 138.8, 137.5, 137.4, 135.5, 130.1, 129.8, 129.7, 129.4, 129.2, 129.1, 128.9, 128.6, 128.5, 128.4, 128.2, 128.1, 128.0, 127.5, 126.2, 125.3, 78.0, 76.6, 21.2, 20.9. Anal. Calcd for C100H82Cl4N10O4Pd2: C, 65.19; H, 4.49; N, 7.60. Found: C, 65.08; H, 4.62; N, 7.14. Synthesis of Bis(imidazoline) NCN Pincer Pd(II) Bromide Complexes 5a−d. The 2-bromo-1,3-bis(amido alcohol) (1.0 mmol) reacted with thionyl chloride (0.7 mL, 9.6 mmol) at reflux for 12 h. Excess thionyl chloride was evaporated. The residue was dissolved in dry CH2Cl2 (2 mL) and this solution added dropwise to a solution of triethylamine (0.3 mL, 2.2 mmol) and p-toluidine (2 mmol) in CH2Cl2 (10 mL) at 0 °C. The mixture was then warmed to room temperature and stirred for 12 h. After that, 10% NaOH (5 mL) was added and the mixture was stirred for another 12 h. The aqueous solution was extracted with dichloromethane, and the organic layer was washed with brine, dried over Na2SO4, and evaporated. The crude product was purified by preparative TLC on silica gel plates to give 2bromo-1,3-bis(imidazoline)benzenes 4a−d. Then a mixture of bis(imidazoline)benzene 4 (0.3 mmol) and Pd2(dba)3 (206.0 mg, 0.225 mmol) in toluene (15 mL) was stirred at room temperature for 48 h. The solvent was evaporated in vacuo, and purification by column chromatography on silica gel provided the pincer Pd(II) bromide complexes 5a−d. 2-Bromo-1,3-bis((S)-4-phenyl-1-p-tolyl-4,5-dihydro-1H-imidazol2-yl)benzene (4a). Pale yellow solid (319.0 mg, 51%). Mp: 101−103 °C. [α]D20 = −110° (c 0.188, CH2Cl2). 1H NMR (400 MHz, CDCl3): 1807

dx.doi.org/10.1021/om500144b | Organometallics 2014, 33, 1801−1811

Organometallics

Article

39.0. 31P{1H} NMR (162 MHz, CDCl3): δ 34.5. HRMS (positive ESI): [M + H]+ calcd for C31H26O2P 461.1670, found 461.1671. (S)-3-(4-Bromophenyl)-3-(diphenylphosphinyl)-1-(4methoxyphenyl)propan-1-one (7j). White solid (20.8 mg, 20%). Mp: 245−246 °C. The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2-propanol (90/10) and flow rate 0.5 mL/min and detected at a UV wavelength of 228 nm. Retention times: 23.2 min (major), 30.2 min, 88% ee. [α]D20 = −146° (c 0.164, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 7.99−7.94 (m, 2H), 7.82 (d, JHH = 8.9 Hz, 2H), 7.53−7.52 (m, 5H), 7.39−7.35 (m, 1H), 7.30−7.26 (m, 6H), 6.84 (d, JHH = 8.9 Hz, 2H), 4.44 (ddd, JHH = 9.1 and 2.2 Hz, JHP = 6.6 Hz, 1H, PCHCH2), 3.92 (ddd, JHH = 17.9 and 10.6 Hz, JHP = 4.2 Hz, 1H, PCHCHH), 3.81 (s, 3H, OCH3), 3.28 (ddd, JHH = 17.9 and 2.2 Hz, JHP = 10.8 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 194.8 (d, JCP = 13.3 Hz), 163.8, 135.2 (d, JCP = 5.7 Hz), 131.93 (d, JCP = 51.0 Hz), 131.90 (d, JCP = 51.0 Hz), 131.7 (d, JCP = 28.7 Hz), 131.5 (d, JCP = 5.7 Hz), 131.4 (d, JCP = 1.4 Hz), 131.2 (d, JCP = 8.6 Hz), 130.9 (d, JCP = 8.9 Hz), 130.6, 130.5, 129.3, 129.0 (d, JCP = 11.2 Hz), 128.3 (d, JCP = 11.9 Hz), 121.1 (d, JCP = 3.1 Hz), 113.8, 55.5, 40.6 (d, JCP = 68.9 Hz), 38.4. 31P{1H} NMR (162 MHz, CDCl3): δ 34.2. HRMS (positive ESI): [M + H]+ calcd for C28H25BrO3P 519.0725, found 519.0726. (S)-3-(4-Bromophenyl)-3-(diphenylphosphinyl)-1-(4-nitrophenyl)propan-1-one (7l). White solid (93.3 mg, 87%). Mp: 246−247 °C. The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2-propanol (85/15) and flow rate 0.5 mL/min and detected at a UV wavelength of 228 nm. Retention times: 37.8 min (major), 52.4 min, 85% ee. [α]D20 = −126° (c 0.118, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.22 (d, JHH = 8.9 Hz, 2H), 7.99−7.94 (m, 4H), 7.56−7.48 (m, 5H), 7.41−7.37 (m, 1H), 7.32−7.25 (m, 6H), 4.40 (ddd, JHH = 10.0 and 2.4 Hz, JHP = 7.6 Hz, 1H, PCHCH2), 3.95 (ddd, JHH = 18.4 and 10.0 Hz, JHP = 4.4 Hz, 1H, PCHCHH), 3.43 (ddd, JHH = 18.4 and 2.4 Hz, JHP = 11.2 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 195.3 (d, JCP = 13.0 Hz), 150.5, 140.5, 134.8 (d, JCP = 5.6 Hz), 132.10 (d, JCP = 49.2 Hz), 132.08 (d, JCP = 49.4 Hz), 131.6 (d, JCP = 1.7 Hz), 131.5 (d, JCP = 15.5 Hz), 131.3 (d, JCP = 5.5 Hz), 131.2 (d, JCP = 8.6 Hz), 130.9 (d, JCP = 8.9 Hz), 130.4 (d, JCP = 5.2 Hz), 129.14, 129.11 (d, JCP = 11.5 Hz), 128.4 (d, JCP = 11.9 Hz), 123.8, 121.5 (d, JCP = 2.9 Hz), 40.7 (d, JCP = 68.3 Hz), 39.6. 31 1 P{ H} NMR (162 MHz, CDCl3): δ 33.3. HRMS (positive ESI): [M + H]+ calcd for C27H22BrNO4P 534.0470, found 534.0472. (S)-1,3-Bis(4-bromophenyl)-3-(diphenylphosphinyl)propan-1-one (7m). White solid (102.2 mg, 90%). Mp: 261−262 °C. The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2-propanol (85/15) and flow rate 0.7 mL/min and detected at a UV wavelength of 228 nm. Retention times: 10.7 min (major), 13.1 min, 89% ee. [α]D20 = −145° (c 0.252, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 7.98−7.93 (m, 2H), 7.68 (d, JHH = 8.6 Hz, 2H), 7.54−7.47 (m, 7H), 7.39−7.35 (m, 1H), 7.31−7.24 (m, 6H), 4.40 (ddd, JHH = 10.0 and 2.5 Hz, JHP = 6.8 Hz, 1H, PCHCH2), 3.89 (ddd, JHH = 18.1 and 10.4 Hz, JHP = 4.6 Hz, 1H, PCHCHH), 3.33 (ddd, JHH = 18.1 and 2.5 Hz, JHP = 10.7 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 195.5 (d, JCP = 13.2 Hz), 135.0 (d, JCP = 5.5 Hz), 134.9, 131.99 (d, JCP = 50.7 Hz), 131.96 (d, JCP = 50.6 Hz), 131.94, 131.6 (d, JCP = 15.7 Hz), 131.5 (d, JCP = 1.5 Hz), 131.4 (d, JCP = 5.7 Hz), 131.2 (d, JCP = 8.6 Hz), 130.9 (d, JCP = 8.9 Hz), 130.6 (d, JCP = 8.8 Hz), 129.6, 129.1 (d, JCP = 11.4 Hz), 128.8, 128.3 (d, JCP = 11.8 Hz), 121.3 (d, JCP = 3.0 Hz), 40.6 (d, JCP = 68.7 Hz), 38.9. 31 1 P{ H} NMR (162 MHz, CDCl3): δ 33.6. HRMS (positive ESI): [M + Na]+ calcd for C27H21Br2NaO2P 588.9544, found 588.9546. (S)-2-(3-(Diphenylphosphinyl)-3-phenylpropionyl)pyridine NOxide (7o). White solid (71.8 mg, 84%). Mp: 169−170 °C. The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min and detected at a UV wavelength of 228 nm. Retention times: 17.1 min (major), 22.8 min, 80% ee. [α]D20 = −110° (c 0.386, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.11 (d, JHH = 6.5 Hz, 1H), 8.01−7.96 (m, 2H), 7.55−7.51 (m, 3H), 7.47−7.43 (m, 2H), 7.37−7.33 (m, 1H), 7.27−7.22 (m, 3H), 7.15−7.05 (m, 7H), 4.44 (ddd, JHH = 12.8 and 4.0 Hz, JHP = 8.9 Hz, 1H, PCHCH2), 4.06 (ddd, JHH = 18.0 and 10.8 Hz,

3.97−3.94 (m, 2H, NCH2), 2.40 (s, 6H, CH3), 1.12 (s, 18H, C(CH3)3). 13C NMR (100 MHz, CDCl3): δ 171.4, 169.3, 137.9, 137.0, 133.0, 130.3, 126.3, 126.2, 121.8, 69.4, 58.0, 36.3, 26.8, 21.2. Anal. Calcd for C34H41BrN4Pd: C, 59.01; H, 5.97; N, 8.10. Found: C, 58.53; H, 6.06; N, 7.65. 2,6-Bis((S,S)-1-p-tolyl-4,5-diphenyl-4,5-dihydro-1H-imidazol-2yl)phenylpalladium(II) Bromide (5d). Yellow solid (135.3 mg, 51%). Mp: 211−212 °C. [α]D20 = +92° (c 0.110, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 7.41−7.39 (m, 5H, ArH), 7.36−7.24 (m, 18H, ArH), 7.07 (br s, 5H, ArH), 6.65 (t, J = 7.8 Hz, 1H, ArH), 6.45 (d, J = 7.8 Hz, 2H, ArH), 5.31 (d, J = 5.4 Hz, 2H, NCH), 4.83 (d, J = 5.4 Hz, 2H, NCH), 2.32 (s, 6H, CH3). 13C NMR (100 MHz, CDCl3): δ 175.1, 169.5, 142.9, 140.3, 138.2, 136.2, 133.3, 130.2, 129.1, 128.7, 128.6, 127.6, 127.2, 126.8, 122.2, 79.5, 75.1, 21.2. Anal. Calcd for C50H41BrN4Pd·0.5CH2Cl2: C, 65.45; H, 4.57; N, 6.05. Found: C, 65.19; H, 4.60; N, 5.72. General Procedure for the Enantioselective Hydrophosphination of Enones with Diphenylphosphine. Under an N2 atmosphere, a Schlenk tube equipped with a magnetic stirring bar was charged with pincer Pd catalyst (5 mol %), KOAc (2.0 mg, 10 mol %), and dry toluene (2 mL). The mixture was stirred for 30 min at 0 °C or room temperature (for the hydrophosphination of 2-alkenoyl pyridine N-oxides). Then diphenylphosphine (37.2 mg, 0.2 mmol) was added, and stirring was continued for another 30 min. After addition of enone (0.3 mmol), the resulting mixture was stirred for an additional 12 h at 0 or 25 °C (for 2-alkenoyl pyridine N-oxides) and then directly oxidized with H2O2 aqueous solution (30%, 60 μL). After the mixture was stirred at room temperature for 2 h, saturated Na2S2O3 aqueous solution was added. The organic layer was separated and the aqueous phase extracted with CH2Cl2. The combined organic phases were dried (Na2SO4), and the volatiles were removed under reduced pressure. Purification by column chromatography on silica gel provided the chiral phosphine oxide products. (S)-3-(Diphenylphosphinyl)-3-(3-nitrophenyl)-1-phenylpropan-1one (7e). White solid (67.4 mg, 74%). Mp: 248−249 °C. The enantiomeric excess was determined on a Daicel Chiralpak AD-H column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min and detected at a UV wavelength of 228 nm. Retention times: 15.5 min (major), 27.6 min, 84% ee. [α]D20 = −156° (c 0.116, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.17 (d, JHH = 1.7 Hz, 1H), 8.02−7.95 (m, 3H), 7.86−7.79 (m, 3H), 7.57−7.48 (m, 6H), 7.42−7.28 (m, 6H), 4.58 (ddd, JHH = 10.1 and 2.2 Hz, JHP = 6.9 Hz, 1H, PCHCH2), 4.05 (ddd, JHH = 18.4 and 10.7 Hz, JHP = 4.3 Hz, 1H, PCHCHH), 3.44 (ddd, JHH = 18.4 and 2.3 Hz, JHP = 10.5 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 196.0 (d, JCP = 13.1 Hz), 147.9, 138.4 (d, JCP = 5.7 Hz), 135.9, 135.5 (d, JCP = 5.0 Hz), 133.7, 133.22 (d, JCP = 50.5 Hz), 133.20 (d, JCP = 50.5 Hz), 131.18 (d, JCP = 8.6 Hz), 131.17 (d, JCP = 35.4 Hz), 130.7 (d, JCP = 9.0 Hz), 130.2 (d, JCP = 31.1 Hz), 129.198, 129.197 (d, JCP = 11.4 Hz), 128.7, 128.5 (d, JCP = 11.9 Hz), 128.1, 125.0 (d, JCP = 5.8 Hz), 122.1, 41.1 (d, JCP = 67.5 Hz), 38.7. 31 1 P{ H} NMR (162 MHz, CDCl3): δ 33.5. HRMS (positive ESI): [M + H]+ calcd for C27H23NO4P 456.1365, found 456.1365. (S)-3-(Diphenylphosphinyl)-3-(naphthalen-1-yl)-1-phenylpropan-1-one (7g). White solid (80.1 mg, 87%). Mp: 225−226 °C. The enantiomeric excess was determined on a Daicel Chiralpak AD-H column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min and detected at a UV wavelength of 228 nm. Retention times: 19.2 min (major), 23.1 min, 89% ee. [α]D20 = −166° (c 0.142, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.40 (s, 1H), 8.05−8.00 (m, 2H), 7.91− 7.87 (m, 2H), 7.81−7.77 (m, 2H), 7.58−7.42 (m, 9H), 7.36−7.32 (m, 1H), 7.27−7.23 (m, 2H), 7.17−7.07 (m, 3H), 4.53 (ddd, JHH = 9.8 and 2.3 Hz, JHP = 6.7 Hz, 1H, PCHCH2), 4.19 (ddd, JHH = 17.9 and 10.4 Hz, JHP = 4.4 Hz, 1H, PCHCHH), 3.52 (ddd, JHH = 17.9 and 2.4 Hz, JHP = 11.1 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 196.5 (d, JCP = 13.3 Hz), 136.0 (d, JCP = 5.7 Hz), 135.6, 133.7, 132.4, 132.0 (d, JCP = 25.2 Hz), 131.8 (d, JCP = 63.2 Hz), 131.7 (d, JCP = 63.4 Hz), 131.3 (d, JCP = 8.4 Hz), 131.2, 131.0 (d, JCP = 8.9 Hz), 130.2, 129.9 (d, JCP = 5.7 Hz), 129.6, 129.0 (d, JCP = 11.2 Hz), 128.7, 128.36 (d, JCP = 2.2 Hz), 128.34 (d, JCP = 1.9 Hz), 128.1 (d, JCP = 11.8 Hz), 127.7, 127.1 (d, JCP = 2.2 Hz), 126.8, 123.6, 41.2 (d, JCP = 69.1 Hz), 1808

dx.doi.org/10.1021/om500144b | Organometallics 2014, 33, 1801−1811

Organometallics

Article

JHP = 8.0 Hz, 1H, PCHCHH), 3.73 (ddd, JHH = 18.0 and 4.0 Hz, JHP = 8.6 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 195.5 (d, JCP = 15.1 Hz), 146.7, 140.1, 135.3 (d, JCP = 5.7 Hz), 131.78 (d, JCP = 58.5 Hz), 131.75 (d, JCP = 58.6 Hz), 131.6 (d, JCP = 8.8 Hz), 131.2 (d, JCP = 8.8 Hz), 130.8, 130.6, 129.8 (d, JCP = 5.2 Hz), 128.8 (d, JCP = 11.2 Hz), 128.2 (d, JCP = 1.9 Hz), 128.1 (d, JCP = 11.7 Hz), 127.8, 127.1 (d, JCP = 2.6 Hz), 126.6, 125.4, 43.0, 41.8 (d, JCP = 66.9 Hz). 31 1 P{ H} NMR (162 MHz, CDCl3): δ 32.8. HRMS (positive ESI): [M + H]+ calcd for C26H23NO3P 428.1416, found 428.1413. (S)-2-(3-(4-Bromophenyl)-3-(diphenylphosphinyl)propionyl)pyridine N-Oxide (7p). Pale yellow solid (86.5 mg, 85%). Mp: 208− 209 °C. The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min and detected at a UV wavelength of 228 nm. Retention times: 18.3 min (major), 28.9 min, 87% ee. [α]D20 = −121° (c 0.462, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.10 (d, JHH = 6.4 Hz, 1H), 7.99−7.94 (m, 2H), 7.55−7.47 (m, 5H), 7.40−7.36 (m, 1H), 7.31− 7.21 (m, 5H), 7.19−7.06 (m, 4H), 4.42 (ddd, JHH = 12.2 and 3.7 Hz, JHP = 8.8 Hz, 1H, PCHCH2), 4.06 (ddd, JHH = 18.0 and 10.8 Hz, JHP = 7.3 Hz, 1H, PCHCHH), 3.71 (ddd, JHH = 18.0 and 3.7 Hz, JHP = 8.8 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 194.9 (d, JCP = 14.9 Hz), 146.3, 140.3, 134.6 (d, JCP = 5.8 Hz), 131.93 (d, JCP = 48.9 Hz), 131.91 (d, JCP = 46.2 Hz), 131.48 (d, JCP = 9.0 Hz), 131.47 (d, JCP = 4.9 Hz), 131.3 (d, JCP = 1.6 Hz), 131.1 (d, JCP = 8.8 Hz), 130.7, 130.3, 128.9 (d, JCP = 11.4 Hz), 128.3 (d, JCP = 11.7 Hz), 128.1, 126.8, 125.3, 121.2 (d, JCP = 3.4 Hz), 43.0, 41.2 (d, JCP = 66.7 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 32.1. HRMS (positive ESI): [M + H]+ calcd for C26H22BrNO3P 506.0521, found 506.0519. (S)-2-(3-(2-Bromophenyl)-3-(diphenylphosphinyl)propionyl)pyridine N-Oxide (7q). Pale yellow oil (81.0 mg, 80%). The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min and detected at a UV wavelength of 228 nm. Retention times: 13.3 min (major), 22.3 min, 85% ee. [α]D20 = −96° (c 0.358, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.06−8.02 (m, 3H), 7.73−7.70 (m, 1H), 7.53−7.52 (m, 3H), 7.31−7.16 (m, 5H), 7.13−7.07 (m, 3H), 7.02− 6.98 (m, 2H), 6.90−6.85 (m, 1H), 5.01 (ddd, JHH = 12.0 and 4.2 Hz, JHP = 8.0 Hz, 1H, PCHCH2), 3.91 (ddd, JHH = 19.4 and 11.0 Hz, JHP = 8.3 Hz, 1H, PCHCHH), 3.76 (ddd, JHH = 16.9 and 4.2 Hz, JHP = 7.4 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 194.9 (d, JCP = 15.7 Hz), 146.4, 140.3, 135.0 (d, JCP = 5.2 Hz), 132.3 (d, JCP = 2.3 Hz), 131.8 (d, JCP = 8.7 Hz), 131.30 (d, JCP = 56.0 Hz), 131.26 (d, JCP = 57.4 Hz), 131.2, 131.1, 130.8, 129.9, 128.9 (d, JCP = 11.4 Hz), 128.6 (d, JCP = 2.3 Hz), 128.0, 127.8 (d, JCP = 11.8 Hz), 127.7 (d, JCP = 2.2 Hz), 126.8, 126.4 (d, JCP = 7.3 Hz), 125.2, 43.4, 39.7 (d, JCP = 65.6 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 32.8. HRMS (positive ESI): [M + H]+ calcd for C26H22BrNO3P 506.0521, found 506.0523. (S)-2-(3-(4-Chlorophenyl)-3-(diphenylphosphinyl)propionyl)pyridine N-Oxide (7r). White solid (72.0 mg, 78%). Mp: 210−212 °C. The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min and detected at a UV wavelength of 228 nm. Retention times: 16.7 min (major), 25.1 min, 89% ee. [α]D20 = −134° (c 0.800, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.11 (d, JHH = 6.5 Hz, 1H), 7.99−7.94 (m, 2H), 7.56−7.46 (m, 5H), 7.40−7.36 (m, 1H), 7.31−7.27 (m, 3H), 7.19−7.06 (m, 6H), 4.43 (ddd, JHH = 12.4 and 3.8 Hz, JHP = 8.7 Hz, 1H, PCHCH2), 4.05 (ddd, JHH = 18.0 and 10.8 Hz, JHP = 7.4 Hz, 1H, PCHCHH), 3.71 (ddd, JHH = 18.0 and 3.8 Hz, JHP = 8.7 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 195.0 (d, JCP = 14.8 Hz), 146.4, 140.3, 134.0 (d, JCP = 5.7 Hz), 133.0 (d, JCP = 3.2 Hz), 131.93 (d, JCP = 50.3 Hz), 131.90 (d, JCP = 50.5 Hz), 131.5 (d, JCP = 8.7 Hz), 131.10 (d, JCP = 5.8 Hz), 131.08 (d, JCP = 8.4 Hz), 130.7, 130.3, 128.9 (d, JCP = 11.4 Hz), 128.33 (d, JCP = 2.2 Hz), 128.25 (d, JCP = 11.9 Hz), 128.0, 126.8, 125.3, 43.1, 41.2 (d, JCP = 66.7 Hz). 31 1 P{ H} NMR (162 MHz, CDCl3): δ 32.4. HRMS (positive ESI): [M + H]+ calcd for C26H22ClNO3P 462.1026, found 462.1028. (S)-2-(3-(Diphenylphosphinyl)-3-(4-nitrophenyl)propionyl)pyridine N-Oxide (7s). Pale yellow solid (85.1 mg, 90%). Mp: 197− 198 °C. The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2-propanol (70/30) and flow rate 1.0

mL/min and detected at a UV wavelength of 228 nm. Retention times: 29.3 min (major), 61.4 min, 87% ee. [α]D20 = −170° (c 0.854, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.13 (d, JHH = 6.4 Hz, 1H), 8.01−7.97 (m, 4H), 7.58−7.50 (m, 5H), 7.45−7.38 (m, 3H), 7.32− 7.28 (m, 4H), 7.17 (t, JHH = 7.4 Hz, 1H), 4.59 (ddd, JHH = 11.2 and 3.4 Hz, JHP = 8.6 Hz, 1H, PCHCH2), 4.20 (ddd, JHH = 18.2 and 10.8 Hz, JHP = 6.7 Hz, 1H, PCHCHH), 3.79 (ddd, JHH = 18.4 and 3.4 Hz, JHP = 9.1 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 194.2 (d, JCP = 14.6 Hz), 146.8 (d, JCP = 2.7 Hz), 145.9, 143.7 (d, JCP = 5.7 Hz), 140.5, 132.22 (d, JCP = 45.9 Hz), 132.20 (d, JCP = 45.9 Hz), 131.4 (d, JCP = 8.7 Hz), 130.9 (d, JCP = 8.8 Hz), 130.7 (d, JCP = 5.1 Hz), 130.3, 129.8, 129.1 (d, JCP = 11.6 Hz), 128.5 (d, JCP = 12.0 Hz), 128.4 (d, JCP = 2.1 Hz), 127.0, 125.4, 123.2 (d, JCP = 1.4 Hz), 43.1, 41.9 (d, JCP = 65.0 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 31.9. HRMS (positive ESI): [M + H]+ calcd for C26H22N2O5P 473.1266, found 473.1269. (S)-2-(3-(Diphenylphosphinyl)-3-(3-nitrophenyl)propionyl)pyridine N-Oxide (7t). Pale yellow solid (76.5 mg, 81%). Mp: 214− 215 °C. The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2-propanol (60/40) and flow rate 0.8 mL/min and detected at a UV wavelength of 228 nm. Retention times: 18.9 min (major), 30.5 min, 92% ee. [α]D20 = −128° (c 0.730, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.13 (d, JHH = 6.4 Hz, 1H), 8.02−7.96 (m, 3H), 7.90 (d, JHH = 1.9 Hz, 1H), 7.76 (d, JHH = 7.0 Hz, 1H), 7.58−7.50 (m, 5H), 7.40−7.27 (m, 6H), 7.17−7.13 (m, 1H), 4.59 (ddd, JHH = 12.0 and 3.6 Hz, JHP = 8.7 Hz, 1H, PCHCH2), 4.16 (ddd, JHH = 18.2 and 10.7 Hz, JHP = 6.9 Hz, 1H, PCHCHH), 3.80 (ddd, JHH = 18.4 and 3.6 Hz, JHP = 9.1 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 194.3 (d, JCP = 14.5 Hz), 147.7, 146.0, 140.5, 137.9 (d, JCP = 5.7 Hz), 135.7 (d, JCP = 4.4 Hz), 132.19 (d, JCP = 44.9 Hz), 132.16 (d, JCP = 45.1 Hz), 131.5 (d, JCP = 8.8 Hz), 130.9 (d, JCP = 8.8 Hz), 130.3, 129.8, 129.2 (d, JCP = 2.0 Hz), 129.0 (d, JCP = 11.6 Hz), 128.4 (d, JCP = 11.9 Hz), 128.3, 126.9, 125.3, 124.9 (d, JCP = 5.7 Hz), 122.1 (d, JCP = 2.1 Hz), 43.0, 41.6 (d, JCP = 65.6 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 32.1. HRMS (positive ESI): [M + H]+ calcd for C26H22N2O5P 473.1266, found 473.1270. (S)-2-(3-(Diphenylphosphinyl)-3-(4-methylphenyl)propionyl)pyridine N-Oxide (7u). Pale yellow solid (69.8 mg, 79%). Mp: 185− 187 °C. The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min and detected at a UV wavelength of 228 nm. Retention times: 14.3 min (major), 21.4 min, 63% ee. [α]D20 = −89° (c 0.736, CH2Cl2). 1 H NMR (400 MHz, CDCl3): δ 8.10 (d, JHH = 6.5 Hz, 1H), 7.99−7.94 (m, 2H), 7.54−7.46 (m, 5H), 7.38−7.34 (m, 1H), 7.28−7.24 (m, 3H), 7.08 (d, JHH = 4.6 Hz, 2H), 7.03−7.01 (m, 2H), 6.89 (d, JHH = 7.9 Hz, 2H), 4.41 (ddd, JHH = 13.1 and 4.0 Hz, JHP = 10.7 Hz, 1H, PCHCH2), 4.03 (ddd, JHH = 18.0 and 10.7 Hz, JHP = 8.0 Hz, 1H, PCHCHH), 3.71 (ddd, JHH = 17.7 and 3.9 Hz, JHP = 8.6 Hz, 1H, PCHCHH), 2.20 (s, 3H, CH3). 13C NMR (100 MHz, CDCl3): δ 195.5 (d, JCP = 15.2 Hz), 146.6, 140.1, 136.7 (d, JCP = 2.7 Hz), 132.0 (d, JCP = 6.1 Hz), 131.72 (d, JCP = 53.6 Hz), 131.70 (d, JCP = 53.6 Hz), 131.6 (d, JCP = 8.7 Hz), 131.3 (d, JCP = 8.7 Hz), 130.9, 130.8, 129.6 (d, JCP = 5.2 Hz), 128.9 (d, JCP = 1.9 Hz), 128.8 (d, JCP = 11.2 Hz), 128.1 (d, JCP = 11.6 Hz), 127.8, 126.7, 125.3, 43.0, 41.4 (d, JCP = 67.3 Hz), 21.0. 31P{1H} NMR (162 MHz, CDCl3): δ 32.6. HRMS (positive ESI): [M + H]+ calcd for C27H25NO3P 442.1572, found 442.1570. (S)-2-(3-(Diphenylphosphinyl)-3-(4-methoxyphenyl)propionyl)pyridine N-Oxide (7v). Pale yellow solid (65.5 mg, 72%). Mp: 196− 198 °C. The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min and detected at a UV wavelength of 228 nm. Retention times: 21.9 min (major), 30.9 min, 77% ee. [α]D20 = −143° (c 0.116, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.11 (d, JHH = 6.5 Hz, 1H), 7.99−7.94 (m, 2H), 7.55−7.44 (m, 5H), 7.38−7.34 (m, 1H), 7.28− 7.24 (m, 3H), 7.10−7.04 (m, 4H), 6.63 (d, JHH = 8.6 Hz, 2H), 4.39 (ddd, JHH = 12.7 and 3.9 Hz, JHP = 9.0 Hz, 1H, PCHCH2), 4.01 (ddd, JHH = 17.8 and 11.0 Hz, JHP = 7.8 Hz, 1H, PCHCHH), 3.73−3.65 (m, 4H, PCHCHH and OCH3).13C NMR (100 MHz, CDCl3): δ 195.6 (d, JCP = 15.4 Hz), 158.6 (d, JCP = 2.3 Hz), 146.7, 140.1, 131.72 (d, JCP = 55.4 Hz), 131.69 (d, JCP = 55.4 Hz), 131.5 (d, JCP = 8.7 Hz), 131.2 (d, 1809

dx.doi.org/10.1021/om500144b | Organometallics 2014, 33, 1801−1811

Organometallics

Article

propanol (60/40) and flow rate 1.0 mL/min and detected at a UV wavelength of 228 nm. Retention times: 12.0 min (major), 17.1 min, 64% ee. [α]D20 = −57° (c 0.327, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.14 (d, JHH = 6.3 Hz, 1H), 7.94−7.89 (m, 2H), 7.79−7.74 (m, 2H), 7.53−7.41 (m, 7H), 7.33−7.29 (m, 1H), 7.24−7.13 (m, 6H), 6.30 (dd, J = 4.3, 15.9 Hz, 1H), 6.08 (ddd, JHH = 14.9 and 9.1 Hz, JHP = 5.7 Hz, 1H), 4.20−4.12 (m, 1H, PCHCH2), 3.76 (ddd, JHH = 17.7 and 10.0 Hz, JHP = 8.0 Hz, 1H, PCHCHH), 3.61 (ddd, JHH = 17.5 and 4.0 Hz, JHP = 9.8 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 195.2 (d, JCP = 14.3 Hz), 146.7, 140.3, 136.5 (d, JCP = 2.9 Hz), 135.1 (d, JCP = 11.2 Hz), 132.02 (d, JCP = 21.1 Hz), 131.99 (d, JCP = 21.1 Hz), 131.6 (d, JCP = 8.8 Hz), 131.5 (d, JCP = 8.7 Hz), 130.7, 130.4, 128.8 (d, JCP = 11.3 Hz), 128.5 (d, JCP = 3.1 Hz), 128.45 (d, JCP = 11.5 Hz), 128.0, 127.7, 127.1, 126.3, 125.5, 123.4 (d, JCP = 7.4 Hz), 41.4, 40.0 (d, JCP = 68.5 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 33.1. HRMS (positive ESI): [M + H]+ calcd for C28H25NO3P 454.1572, found 454.1573. (S)-2-(3-(Diphenylphosphinyl)-3-(1-naphthyl)propionyl)pyridine N-Oxide (7aa). Pale yellow oil (66.8 mg, 70%). The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2-propanol (60/40) and flow rate 1.0 mL/min and detected at a UV wavelength of 228 nm. Retention times: 9.7 min (major), 15.2 min, 76% ee. [α]D20 = −64° (c 0.100, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.15−8.10 (m, 2H), 8.01 (d, JHH = 6.4 Hz, 1H), 7.86−7.83 (m, 1H), 7.74 (d, JHH = 8.5 Hz, 1H), 7.62−7.59 (m, 5H), 7.39 (t, JHH = 7.6 Hz, 1H), 7.28−7.15 (m, 4H), 7.08−6.92 (m, 4H), 6.73 (t, JHH = 7.6 Hz, 1H), 6.65−6.62 (m, 1H), 5.48 (ddd, JHH = 13.6 and 4.6 Hz, JHP = 10.4 Hz, 1H, PCHCH2), 4.10 (ddd, JHH = 14.2 and 7.1 Hz, JHP = 3.3 Hz, 1H, PCHCHH), 3.95 (ddd, JHH = 17.2 and 4.6 Hz, JHP = 7.0 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 195.7 (d, JCP = 15.5 Hz), 146.6, 139.9, 133.2, 132.1, 132.0 (d, JCP = 33.2 Hz), 131.99 (d, JCP = 39.3 Hz), 131.9, 131.8 (d, JCP = 8.6 Hz), 131.3 (d, JCP = 2.7 Hz), 130.9, 130.8 (d, JCP = 9.1 Hz), 130.4, 128.9 (d, JCP = 11.2 Hz), 128.5, 127.7, 127.6 (d, JCP = 11.2 Hz), 126.4, 125.8, 125.4 (d, JCP = 2.5 Hz), 125.2, 125.1, 122.2, 44.2, 34.5 (d, JCP = 66.8 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 32.6. X-ray Diffraction Studies. Crystals of 3 and 5b (CCDC file numbers 980716 and 980605) were obtained by recrystallization from CH2Cl2/n-hexane at ambient temperature. The data were collected on an Oxford Diffraction Gemini E diffractometer with graphitemonochromated Cu Kα radiation (λ = 1.5418 Å for complex 3) or Mo Kα radiation (λ = 0.7107 Å) at ambient temperature. The structures were solved by direct methods using the SHELXS-97 program, and all non-hydrogen atoms were refined anisotropically on F2 by the full-matrix least-squares technique, which used the SHELXL97 crystallographic software package.23 The hydrogen atoms were included but not refined. Details of the crystal structure determination are summarized in Table S1 in the Supporting Information.

JCP = 8.8 Hz), 131.0, 130.8 (d, JCP = 5.4 Hz), 130.7, 128.8 (d, JCP = 11.2), 128.1 (d, JCP = 11.6), 127.8, 127.0 (d, JCP = 5.9 Hz), 126.7, 125.3, 113.6 (d, JCP = 1.9 Hz), 55.1, 43.0, 40.9 (d, JCP = 67.8 Hz). 31 1 P{ H} NMR (162 MHz, CDCl3): δ 32.6. HRMS (positive ESI): [M + H]+ calcd for C27H25NO4P 458.1521, found 458.1525. (S)-2-(3-(Diphenylphosphinyl)-3-(3-methoxyphenyl)propionyl)pyridine N-Oxide (7w). Pale yellow oil (75.2 mg, 82%). The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min and detected at a UV wavelength of 228 nm. Retention times: 17.0 min (major), 24.3 min, 78% ee. [α]D20 = −95° (c 0.383, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.10 (d, JHH = 6.5 Hz, 1H), 8.00−7.95 (m, 2H), 7.54−7.45 (m, 5H), 7.38−7.33 (m, 1H), 7.28−7.23 (m, 3H), 7.11−7.08 (m, 2H), 6.99 (t, JHH = 7.9 Hz, 1H), 6.72 (d, JHH= 7.4 Hz, 1H), 6.67−6.62 (m, 2H), 4.43 (ddd, JHH = 13.2 and 4.1 Hz, JHP = 10.7 Hz, 1H, PCHCH2), 4.06 (ddd, JHH = 18.0 and 10.8 Hz, JHP = 8.2 Hz, 1H, PCHCHH), 3.72 (ddd, JHH = 17.8 and 4.1 Hz, JHP = 8.6 Hz, 1H, PCHCHH), 3.60 (s, 3H, OCH3). 13C NMR (100 MHz, CDCl3): δ 195.4 (d, JCP = 14.8 Hz), 159.2 (d, JCP = 2.1 Hz), 146.6, 140.1, 136.7 (d, JCP = 5.5 Hz), 131.8 (d, JCP = 48.2 Hz), 131.78 (d, JCP = 54.3 Hz), 131.5 (d, JCP = 8.6 Hz), 131.2 (d, JCP = 8.8 Hz), 130.8, 130.6, 129.1 (d, JCP = 1.7 Hz), 128.8 (d, JCP = 11.5 Hz), 128.1 (d, JCP = 11.7 Hz), 127.8, 126.7, 125.4, 122.2 (d, JCP = 5.2 Hz), 114.7 (d, JCP = 5.2 Hz), 113.5 (d, JCP = 2.3 Hz), 55.1, 42.8, 41.9 (d, JCP = 66.6 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 32.8. HRMS (positive ESI): [M + H]+ calcd for C27H25NO4P 458.1521, found 458.1518. (S)-2-(3-(Diphenylphosphinyl)-3-(2-furanyl)propionyl)pyridine NOxide (7x). Pale yellow oil (52.5 mg, 63%). The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2propanol (60/40) and flow rate 1.0 mL/min and detected at a UV wavelength of 228 nm. Retention times: 11.8 min (major), 17.0 min, 69% ee. [α]D20 = −42° (c 0.270, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.14 (d, JHH = 6.4 Hz, 1H), 7.90−7.85 (m, 2H), 7.55−7.43 (m, 6H), 7.40−7.30 (m, 4H), 7.23−7.19 (m, 1H), 7.11 (s, 1H), 6.17 (dd, JHH = 1.9, 3.2 Hz, 1H), 6.05 (t, JHH = 3.2 Hz, 1H), 4.75 (ddd, JHH = 14.8 and 4.6 Hz, JHP = 10.3 Hz, 1H, PCHCH2), 3.96 (ddd, JHH = 18.2 and 10.1 Hz, JHP = 8.6 Hz, 1H, PCHCHH), 3.78 (ddd, JHH = 18.1 and 4.6 Hz, JHP = 8.6 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 194.9 (d, JCP = 13.1 Hz), 149.0 (d, JCP = 6.2 Hz), 146.4, 141.7 (d, JCP = 2.9 Hz), 140.3, 132.04 (d, JCP = 29.4 Hz), 132.01 (d, JCP = 29.6 Hz), 131.6 (d, JCP = 5.8 Hz), 131.5 (d, JCP = 5.8 Hz), 130.7 (d, JCP = 40.9 Hz), 129.9, 128.7 (d, JCP = 11.7 Hz), 128.2 (d, JCP = 11.7 Hz), 128.0, 127.0, 125.5, 110.8 (d, JCP = 2.8 Hz), 109.0 (d, JCP = 5.9 Hz), 41.1, 36.4 (d, JCP = 68.7 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 31.9. HRMS (positive ESI): [M + H]+ calcd for C24H21NO4P 418.1208, found 418.1209. (S)-2-(3-(Diphenylphosphinyl)-3-(2-thienyl)propionyl)pyridine NOxide (7y). Pale yellow solid (62.4 mg, 72%). Mp: 167−168 °C. The enantiomeric excess was determined on a Daicel Chiralpak AD column with hexane/2-propanol (60/40) and flow rate 1.0 mL/min and detected at a UV wavelength of 228 nm. Retention times: 32.8 min (major), 55.4 min, 78% ee. [α]D20 = −91° (c 0.366, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.12 (d, JHH = 6.4 Hz, 1H), 7.98−7.93 (m, 2H), 7.57−7.52 (m, 5H), 7.43−7.39 (m, 1H), 7.34−7.28 (m, 3H), 7.23−7.20 (m, 1H), 7.16−7.12 (m, 1H), 7.01−6.99 (m, 1H), 6.85 (t, JHH = 2.6 Hz, 1H), 6.77 (dd, JHH = 3.6, 5.0 Hz, 1H), 4.81 (ddd, JHH = 13.8 and 3.9 Hz, JHP = 10.6 Hz, 1H, PCHCH2), 4.00 (ddd, JHH = 17.9 and 10.8 Hz, JHP = 7.4 Hz, 1H, PCHCHH), 3.72 (ddd, JHH = 17.7 and 4.0 Hz, JHP = 8.0 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 195.0 (d, JCP = 14.5 Hz), 146.5, 140.2, 137.1 (d, JCP = 6.5 Hz), 132.00 (d, JCP = 46.2 Hz), 131.92 (d, JCP = 46.0 Hz), 131.8 (d, JCP = 8.8 Hz), 131.3 (d, JCP = 8.8 Hz), 131.1, 130.3, 130.2, 128.9 (d, JCP = 11.5 Hz), 128.2 (d, JCP = 11.7 Hz), 128.0, 127.5 (d, JCP = 6.0 Hz), 126.8 (d, JCP = 2.8 Hz), 125.5, 124.9 (d, JCP = 2.9 Hz), 44.1, 37.3 (d, JCP = 68.8 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 31.8. HRMS (positive ESI): [M + H]+ calcd for C24H21NO3PS 434.0980, found 434.0981. (S,E)-2-(3-(Diphenylphosphinyl)-5-phenyl-4-pentenoyl)pyridine N-Oxide (7z). Pale yellow oil (53.8 mg, 59%). The enantiomeric excess was determined on a Daicel Chiralcel OD-H column with hexane/2-

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ASSOCIATED CONTENT

S Supporting Information *

A table giving crystallographic details for the Pd(II) complexes 3 and 5b, figures giving synthetic routes for the ligands 1a−c and 4a−d, text giving characterization data of the known catalysis products, figures giving NMR spectra of the new compounds 1−5 and NMR spectra of the catalysis products as well as their chiral HPLC spectra, and CIF files giving crystallographic data for complexes 3 and 5b. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Authors

*J.-F.G.: e-mail, [email protected]. *M.-P.S.: tel/fax, (+86)-371-6778-3012; e-mail, mpsong@zzu. edu.cn. Notes

The authors declare no competing financial interest. 1810

dx.doi.org/10.1021/om500144b | Organometallics 2014, 33, 1801−1811

Organometallics

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Organometallics 2007, 26, 3985. (c) Bugarin, A.; Connell, B. T. Organometallics 2008, 27, 4357. (14) Unpublished results. (15) For reviews, see: (a) Newkome, G. R. Chem. Rev. 1993, 93, 2067. (b) Espinet, P.; Soulantica, K. Coord. Chem. Rev. 1999, 193−195, 499. For a review of chiral pyridine-phosphine P,N ligands, see: (c) Chelucci, G.; Orrù, G.; Pinna, G. A. Tetrahedron 2003, 59, 9471. (16) For a recent review on nickel-catalyzed ethylene oligo-/ polymerization, see: (a) Wang, S.; Sun, W.-H.; Redshaw, C. J. Organomet. Chem. 2014, 751, 717. For selected examples, see: (b) Flapper, J.; van Leeuwen, P. W. N. M.; Elsevier, C. J.; Kamer, P. C. J. Organometallics 2009, 28, 3264. (c) Flapper, J.; Kooijman, H.; Lutz, M.; Spek, A. L.; van Leeuwen, P. W. N. M.; Elsevier, C. J.; Kamer, P. C. J. Organometallics 2009, 28, 1180. (17) Mothes, E.; Sentets, S.; Luquin, M. A.; Mathieu, R.; Lugan, N.; Lavigne, G. Organometallics 2008, 27, 1193. (18) Selected examples: (a) Brunel, J.-M.; Constantieux, T.; Labande, A.; Lubatti, F.; Buono, G. Tetrahedron Lett. 1997, 38, 5971. (b) Uenishi, J.; Hamada, M. Tetrahedron: Asymmetry 2001, 12, 2999. (c) Minato, M.; Kaneko, T.; Masauji, S.; Ito, T. J. Organomet. Chem. 2006, 691, 2483. (19) Kwong, F. Y.; Yang, Q.; Mak, T. C. W.; Chan, A. S. C.; Chan, K. S. J. Org. Chem. 2002, 67, 2769. (20) Brasse, M.; Cámpora, J.; Palma, P.; Á lvarez, E.; Cruz, V.; Ramos, J.; Reyes, M. L. Organometallics 2008, 27, 4711. (21) (a) Barroso, S.; Blay, G.; Pedro, J. R. Org. Lett. 2007, 9, 1983. (b) Singh, P. K.; Singh, V. K. Org. Lett. 2008, 10, 4121. (22) (a) Sinisterra, J. V.; Garcia-Raso, A. Synthesis 1984, 6, 502. (b) Shadakshari, U.; Nayak, S. K. Tetrahedron 2001, 57, 8185. (23) (a) Sheldrick, G. M. SHELXS-97, Program for Crystal Structure Solution; University of Gö ttingen, Gö ttingen, Germany, 1997. (b) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure Refinement; University of Göttingen, Göttingen, Germany, 1997.

ACKNOWLEDGMENTS We are grateful to the National Natural Science Foundation of China (21272217), the Program for Science & Technology Innovation Talents in Universities of Henan Province (2012HASTIT003), and the Key Technologies R & D Program of Henan Province (102101210200) for financial support of this work.

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