Experimental
1H NMR spectra were recorded on Bruker Avance 300 (300.13 MHz) and Avance 600 (600.22 MHz) spectrometers; chemical shifts were measured relative to the residual protons of the deuterated solvent (CDCl3). Optical rotations were measured on a Perkin–Elmer 341 polarimeter in a 5-cm cell temperature-stabilized at 25 °C. CD spectrum of equimolar 0.012 M mixture of complex 2 and (S)-BIMBOL in CHCl3 of was measured on a CDS-2 dichrograph (IS RAS) in 400-700 nm range in a 1-mm quartz cell temperature-stabilized at 23 °C. Ordinate value ΔA may be converted into [θ] using the following equations [θ] = ΔA×3298.2/(c×l), were c is concentration in mol/L, l is cell length in cm. All measurements were carried out with a 3-nm spectral resolution; acquisition time 2.4 sec and 35 nm/min scanning rate. The circular dichroism is expressed in molar ellipticity, [θ] (deg×cm2/dmol). Column chromatography was performed with the use of silica gel Kieselgel 60 (Merck). Elemental analyses were carried out in the Laboratory of Microanalysis of the A.N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences. All solvents were purified according to standard procedures. Sigma-Aldrich potassium hydroxide of 99.99% purity was used. ESI mass spectra were run on Finnigan LCQ Advantage instrument.
X-ray Crystallography. Single crystals of 2 and 4b were grown by slow evaporation from acetonitrile and methanol respectively. All diffraction data were collected on a Bruker SMART APEX II CCD diffractometer [l(MoKα) = 0.71072Å, φ- and ω-scans] at 100 K. The substantial redundancy in data allows empirical absorption correction to be performed with SADABS, using multiple measurements of equivalent reflections. The structures were solved by direct methods and refined by the full-matrix least-squares technique on F2 in the anisotropic-isotropic approximation. The hydrogen atoms of the OH-groups as well as the solvate methanol molecules in 4d were localized in the difference-Fourier map and included in the refinement with fixed positional and isotropic displacement parameters. The other hydrogen atoms in 2 and 4d were placed in calculated positions and refined within the riding model with fixed isotropic displacement parameters (Uiso(H) = 1.2Ueq(C)). All calculations were performed with the SHELXTL software package (G.M. Sheldrick, Acta. Cryst. 2008, A64, 112-122). Crystal data and structure refinement parameters are listed in Table 1.
All crystallographic data contained in the supplementary information for this paper have been deposited with the Cambridge Crystallographic Data Center. These data can be obtained free of charge from the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: +44 1223 336033; e-mail: or www.ccdc.cam.ac.uk).
Table 1. Crystal and structure refinement data for 2 and 4d2 / 4d×2CH3OH
CCDC / 821727 / 821004
Formula / C22H15N3NiO3 / C32H23N3O4Ni×
2CH3OH
M, F(000) / 428.08, 440 / 636.33, 1328
Crystal system, Space group / Triclinic, P-1 / Triclinic, P-1
Z (Z’) / 2(1) / 4(2)
a, Å / 5.8536(12) / 11.9350(5)
b, Å / 10.509(3) / 15.7496(6)
c, Å / 15.101(4) / 16.9875(7)
a, ° / 105.254(9) / 67.509(1)
β, ° / 100.896(9) / 81.435(1)
g, ° / 101.217(8) / 80.995(1)
V, Å3 / 850.3(4) / 2900.0(2)
Dcalcd., g∙cm-3, μ, cm-1 / 1.672, 11.73 / 1.457, 7.22
2θmax, ° / 56 / 56
Reflections measured / 7523 / 32489
Independent reflections (Rint) / 3985
(0.034) / 13956
(0.046)
Observed reflections
[I > 2s(I)] / 2797 / 9552
R1 / 0.0428 / 0.0423
wR2 / 0.0945 / 0.0884
GOF / 0.968 / 1.001
Δrmax, Δrmin (eÅ−3) / 0.892 −0.491 / 0.432−0.476
Asymmetric Michael Addition of Complex 1 to Acrylates.
A typical procedure for the Michael addition as illustrated by the synthesis of Ni(II) complex of a Schiff base of PBP and (R)-2-amino-5-methoxy-5-oxo-pentanoic acid (3a). A solution of (S)-BIMBOL (4.7 mg, 7.2×10−3 mmol) in 1 mL of DCM was thoroughly purged with Ar, then KOH (4 mg, 7.2×10−2 mmol) was added with stirring under Ar at room temperature. After 5 min the initial complex 1 (30 mg, 7.2×10−2 mmol) was added under Ar with stirring, followed 5 minutes later by an methylacrylate (0.04 mL, 4.4×10−1 mmol) and the mixture was agitated for an additional 2 min. The progress of the reaction was monitored by TLC (SiO2, CHCl3/Me2CO, 5:1). The reaction was quenched with aqueous 10% AcOH (1 mL) and 2 mL of DCM was added to the resulting mixture. The organic layer was separated, washed with water. The organic layer was evaporated and the residue was purified by chromatography on a SiO2 column (CHCl3/Me2CO, 5:1). The main fraction was evaporated to give the final Michael adduct in 95% yield. The analytically pure sample was obtained after chromatography on LH-20 column (C6H6/C2H5OH, 1:1). M.p. 256-258 °C; [α]D25 −2342 (c 0.5, CHCl3, for a sample of 68% ee). 1H NMR (300 MHz, CDC13, J in Hz): d 1.95 (m, 1H); 2.53 (m, 1H); 2.55 (m, 1H); 3.27 (m, 1H); 3.56 (s, 3H); 4.05 (m, 1H); 6.78 (d, 2H, J = 3.6); 7.23 (m, 2H); 7.37 (m, 1H); 7.48 (m, 1H); 7.54 (m, 3H); 7.92 (d, 1H, J = 7.8), 8.04 (m, 1H); 8.21 (d, 1H, J = 4.8); 8.93 (d, 1H, J=8.4). UV (CHC13): λmax/nm, (log ε) 306 (3.99); 459 (3.65); Anal.: Calcd. for C25H21N3NiO5: C 59.80, H 4.22, N 8.37. Found C 59.81, H 4.18, N 8.5. IR 1734 (νCOOMe), 1678 (Amide I); 1644 (νasCOOˉ), 1606 (C=N), 1328 (νsCOOˉ). MW=502, (m/z=502).
Ni(II) complex of a Schiff base of PBP and (S)-2-amino-5-butoxy-5-oxopentanoic acid (3b). The synthesis was carried out as described for 3a starting with 1 (30 mg, 7.2×10−2 mmol) and butylacrylate (27 mg, 21×10−2 mmol), using (R)- BIMBOL (10% mol) as catalyst; the reaction was complete in 60 min and afforded product in 90% yield. M.p. 184-186 °C. [α]D25 +1689 (c 0.2, CHCl3, for complex with 49% ee). 1H NMR (300 MHz, CDC13, J in Hz): d 0.89 (m, 3H); 1.31 (m, 3H); 1.57 (m, 2H); 1.97 (m, 1H); 2.53 (m, 2H); 3.28 (m, 1H); 4.05 (m, 2H); 6.79 (m, 2H); 7.18 (m, 2H); 7.38 (m, 1H); 7.48 (m, 1H); 7.54 (m, 3H); 7.93 (d, 1H, J=7.8), 8.04 (m, 1H); 8.24 (d, 1H, J=5.4); 8.97 (d, 1H, J=8.7). 13С (75 MHz, CDC13): d:13.70, 19.07, 29.71, 30.00, 30.57, 64.75, 70.37, 121.49, 123.51, 124.13, 126.63, 126.86, 127.01, 128.05, 128.96, 129.17, 129.92, 133.84, 134.71, 140.61, 143.15, 146.95, 146.99, 153.35, 170.05, 172.70, 173.00, 178.95; IR 1732 (νCOOtBu), 1679 (Amide I); 1645 (νasCOOˉ), 1607 (C=N), 1328 (νsCOOˉ). MW=544, (m/z=544).
Ni(II) complex of a Schiff base of PBP and (S)-2-amino-5-oxohexanoic acid (3c). The synthesis was carried out as described for 3a starting from complex 1 (30 mg, 7.2×10−2 mmol) and mеthylvinylketone (20 mg, 28×10−2 mmol), using (R)-BIMBOL (10% mol) as catalyst; the reaction was complete in 8 min and afforded product in yield 95%. M.p. 155-157 °C. [α]D25 +1497 (c 0.2, CHCl3, for complex with 44% ee). 1H NMR (300 MHz, CDC13, J in Hz): d 1.87 (m, 1H); 2.10 (s, 3H); 2.55 (m, 2H); 3.08 (m, 1H); 3.95 (m, 1H); 4.05 (m, 1H); 6.78 (m, 2H); 7.16 (m, 1H); 7.37 (m, 1H); 7.47 (m, 1H); 7.54 (m, 3H); 7.27 (m, 1H); 7.93 (d, 1H, J=6.9), 8.03 (m, 1H); 8.21 (d, 1H, J=4.8); 8.94 (d, 1H, J=8.7). 13С (75 MHz, CDC13): d: 29.17, 30.13, 39.05, 70.12, 121.54, 123.52, 124.21, 126.64, 126.99, 127.06, 127.94, 129.02, 129.19, 129.94, 133.62, 134.68, 140.69, 143.03, 146.90, 153.34, 169.99, 172.48, 179.14, 207.05.; IR 1714 (C=O), 1676 (Amide I); 1644 (νasCOOˉ), 1607 (C=N), 1328 (νsCOOˉ). MW=486, (m/z=486).
Ni(II) complex of a Schiff base of PBP and (S or R)-2-amino-4-cyanobutanoic acid (3d). The synthesis was carried out as described for 3a starting from complex 1 (30 mg, 7.2×10−2 mmol) and acrylonitrile (15 mg, 28×10−2 mmol), using (R)-BIMBOL (10% mol) as catalyst; the reaction was complete in 30 min and afforded product in yield 85%. M.p. 234-235 °C. [α]D25 +360 (c 0.4, CHCl3, for complex with 10% ee). 1H NMR (300 MHz, CDC13, J in Hz): d 2.00 (m, 1H); 2.53 (m, 2H); 2.90 (m, 1H); 4.02 (m, 1H); 6.81 (m, 2H); 7.11 (m, 1H); 7.29 (m, 1H); 7.41 (m, 1H); 7.47 (m, 1H); 7.59 (m, 3H); 7.94 (d, 1H, J=7.5), 8.05 (m, 1H); 8.21 (d, 1H, J=5.1); 8.95 (d, 1H, J=8.7). 13C (75 MHz, CDC13) d: 13.67, 30.97, 69.04, 118.32, 121.64, 123.65, 124.33, 126.90, 127.18, 127.50, 129.33, 129.61, 130.42, 133.35, 134.06, 134.79, 140.84, 143.31, 146.88, 153.19, 170.05, 173.42, 178.08. IR 2925 (C≡N), 1676 (Amide I); 1644 (νasCOOˉ), 1606 (C=N), 1329 (νsCOOˉ). MW=469, (m/z=469).
Ni(II) complex of a Schiff base of PBP and (±)-2-amino-4-carbamoyl-butyric acid (3e). The synthesis was carried out as described 3a starting from complex 1 (30 mg, 7.2×10−2 mmol) and acrylamide (15 mg, 21×10−2 mmol), using (S)- or (R)-BIMBOL (10% mol) as catalyst; the reaction was complete in 20 min and afforded product in yield 95%. Analyticaly pure product was obtained after chromatography of its sample on LH-20 (C6H6/C2H5OH, 1:1). M.p. 293-294 °C (decomp); 1H NMR (300 MHz, CDC13, J in Hz): d 1.79 (m, 1H); 2.14 (m, 1H); 2.68 (m, 1H); 3.13 (m, 1H); 3.79 (m, 1H); 6.60 (m, 2H); 7.06 (m, 2H); 7.14 (m, 1H); 7.36 (m, 4H); 7.72(d, 1H, J=7.5), 7.90 (m, 1H); 7.96 (d, 1H, J=5.1); 8.70 (d, 1H, J=8.4). 13С (75 MHz, CDC13/CD3OD): d: 30.43, 30.76, 33.51, 59.08, 70.35, 92.18, 112.12, 121.79, 123.53, 124.18, 126.61, 126.80, 127.57, 128.02, 129.09, 129.11, 130.02, 133.51, 134.72, 141.19, 146.85, 160.48, 170.12, 180.53. IR 1681 (Amide I); 1651 (Amide I), 1632 (νasCOOˉ), 1604 (C=N), 1326 (νsCOOˉ). MW=487, (m/z=487)3c.
Ni(II) complex of a Schiff base of PBP and (±)-2-amino-5-(4-hydroxybutoxy)-5-oxopentanoic acid (3f). The synthesis was carried out as described for 3a starting from complex 1 (30 mg, 7.2 ×10−2 mmol) and 4-hydroxybutylacrylate (40 mg, 27×10−2 mmol), using (S) or (R)-BIMBOL (10% mol) as catalyst; the reaction was complete in 10 min and afforded product in yield 95%. M.p. 105-107 °C. 1H NMR (300 MHz, CDC13, J in Hz): d 1.63 (m, 3H); 1.94 (m, 2H); 2.90 (m, 2H); 2.39 (m, 1H); 2.57 (m, 1H); 3.35 (m, 1H); 3.61 (m, 1H); 4.07 (m, 3H); 6.79 (m, 2H); 7.32 (m, 3H); 7.46 (m, 1H); 7.57 (m, 3H); 7.92(d, 1H, J=7.8), 8.04 (m, 1H); 8.24 (d, 1H, J=5.1); 8.96 (d, 1H, J=8.7). 13С (75 MHz, CDC13): d: 24.94, 28.96, 29.01, 29.84, 62.06, 64.88, 70.43, 121.65, 123.39, 124.20, 126.71, 126.85, 127.13, 128.15, 128.99, 129.15, 129.95, 133.70, 133.81, 134.84, 140.73, 142.96, 147.02, 153.27, 170.10, 172.85, 173.30, 179.05. IR 3437 (OH), 1730 (νCOOR), 1674 (Amide), 1645 (νasCOOˉ), 1607 (C=N), 1329 (νsCOOˉ). MW=560, (m/z=560).
Asymmetric Michael addition of diethyl ester of malonic acid to complex 2, catalyzed by (R)- or (S)-BIMBOL.
A typical procedure for the Michael addition as illustrated by the synthesis of Ni(II) complex of a Schiff base of PBP and (S)-2-amino-5-ethoxy-4-(ethoxycarbonyl)-5-oxopentanoic acid (4a). The catalyst (S)-BIMBOL (3.8 mg, 5.8×10−3 mmol) was dissolved in 1 mL of DCE and the solution was thoroughly purged with Ar, then KOH (1.6 mg, 2.9×10−2 mmol) was added with stirring under Ar. After 5 min the initial complex 2 (25 mg, 5.8×10−2 mmol) was added under Ar with stirring at 80 °C, followed 5 minutes later by an diethylmalonate (0.018 mL, 11.6×10−2 mmol) and the mixture was agitated for an additional 5 min. The progress of the reaction was monitored by TLC (SiO2, CHCl3/Me2CO, 5:1). The reaction was quenched with aqueous AcOH and DCE was added to the resulting mixture. The organic layer was washed with water, then separated, evaporated and the residue was purified by column chromatography on SiO2 (CHCl3/Me2CO, 5:1). The main fraction was evaporated to give final Michael adduct 17.65 mg (3×10−2 mmol) with 99% chemical yield. M.p. 178-182 °С. [α]D25 +2096 (c 0.35, CHC13, for complex with ee 80%.). Anal.: Calc. for C29H27N3NiO7: C, 59.21; H, 4.63; N, 7.14; Found C, 59.29; H, 4.68; N, 7.11; 1H NMR (300 MHz, CDCl3, J in Hz): d 1.20 (m, 6Н); 2.25 (m, 1Н); 2.69 (m, 1Н); 4.31 (m, 5Н); 4.28 (m, 1Н, СН); 6.78 (d, 2H, J=4.2); 7.23 (m, 1Н); 7.37 (m, 2H, ArH); 7.47 (m, 1H); 7.53(m, 3H); 7.92 (d, 1H, J=7.5); 8.04 (m, 1H); 8.25 (d, 1H, J=5.4 Hz); 8.98 (d, 1H, J=9). IR (n/cm-1; KBr): 1746 (νCOOEt), 1728 (νCOOEt).1678 (Amide I), 1648 (νasCOOˉ); 1606 (C=N), 1678 (νsCOOˉ).
Ni(II) complex of a Schiff base of PBP and (S)-2-amino-5-methoxy-4-(methoxycarbonyl)-5-oxopentanoic acid (4b). The synthesis was carried out as described for 4a starting with 2 (25 mg, 5.8×10−2 mmol) and dimethylmalonate (0.015 mL, 11.6 ×10−2 mmol), using (S)-BIMBOL (10% mol) as catalyst. The reaction was complete in 12 min and afforded the product in a yield of 99%. M.p. 238-240 °С. [α]D25 +2175 (c 0.3, CHC13, for complex with ee 83 %). 1H NMR (300 MHz, CDCl3, J in Hz): d 2.26 (m, 1Н); 2.75 (m, 1Н); 3.63 (d, 6Н, J=13.8); 4.13 (q, 1Н, J=3.6); 4.34 (m, 1Н); 6.77 (d, 2H, J=4.2); 7.24 (m, 1Н); 7.35 (m, 2H); 7.47 (m, 1H); 7.54(m, 3H); 7.92 (d, 1H, J=7.5); 8.03 (m, 1H); 8.22 (d, 1H, J=5.1); 8.95 (d, 1H, J=8.4). 13С (75 MHz, CDC13): d: 32.45, 47.93, 52.89, 53.16, 68.40, 121.55, 123.43, 124.12, 126.55, 126.75, 127.07, 128.23, 129.06, 129.16, 129.95, 133.63, 133.80, 134.90, 140.67, 143.11, 147.00, 153.19, 168.67, 169.86, 170.04, 173.80, 178.36. IR (n/cm-1; KBr): 1758 (νCOOMe), 1740 (νCOOMe), 1669 (νAmide I); 1641 (νasCOOˉ), 1607 (C=N); 1330 (νsCOOˉ). MW=560, (m/z=560).
Ni(II) complex of a Schiff base of PBP and (S)-2-amino-5-tertbuthoxy-4-(tertbuthoxycarbonyl)-5-oxopentanoic acid (4c). The synthesis was carried out as described for 4a synthesis starting with 2 (25 mg, 5.8×10−2 mmol) and ditertbutilmalonate (0.026 mL, 11.6×10−2 mmol ), using (S)-BIMBOL (10% mol) as catalyst; the reaction was complete in 45 min and afforded product in yield 90%. M.p. 110-112 °С. [α]D25 +1186 (c 0.3, CHC13, for complex with ee 45 %). 1H NMR (300 MHz, CDCl3, J in Hz): d 1.35 (d, 18Н, J=2.4); 2.71 (m, 1Н); 3.99 (t, 1Н, J=6.6); 4.08 (m, 1Н); 6.77 (m, 2Н); 7.32 (m, 4H); 7.54 (m, 5Н); 7.91 (d, 1H, J=7.5); 8.02 (t, 1H, J=7.2); 8.24 (d, 1H, J=5.1); 8.97 (d, 1H, J=8.4). 13С (75 MHz, CDC13): d: 27.83, 32.89, 49.93, 69.65, 81.72, 82.10, 121.41, 123.50, 124.06, 126.61, 126.73, 126.96, 128.26, 129.02, 129.12, 129.84, 133.58, 133.71, 134.81, 140.56, 143.23, 147.07, 153.34, 167.66, 168.54, 169.28, 170.07, 173.38, 178.59. IR (n/cm-1; KBr): 1742 (νCOOtBu), 1726 (νCOOtBu), 1682 (Amide I), 1645 (νasCOOˉ), 1607 (C=N); 1327 (νsCOOˉ). MW= 644, (m/z=644).