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Acta Crystallogr Sect E Struct Rep Online. 2009 December 1; 65(Pt 12): o3090.
Published online 2009 November 14. doi:  10.1107/S1600536809046765
PMCID: PMC2971892

N,1-Bis(4-chloro-2-methyl­benz­yl)-3-methyl-2-oxo-1,2,3,4-tetra­hydro­quinoline-3-carboxamide

Abstract

In the title mol­ecule, C27H26Cl2N2O2, the chloro-substituted benzene rings make dihedral angles of 83.29 (9) and 80.81 (9)° with the benzene ring of the tetra­hydro­quinoline group. The dihedral angle formed by the two chloro-substituted benzene rings is 40.87 (12)°. The six-membered N-containing ring is in a half-chair conformation. In the crystal structure, inter­molecular N—H(...)O hydrogen bonds link mol­ecules into centrosymmetric dimers.

Related literature

For the synthesis of the title compound, see: Porosa & Viirre (2009 [triangle]). For a related crystal structure, see: Wang et al. (2007 [triangle])

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Object name is e-65-o3090-scheme1.jpg

Experimental

Crystal data

  • C27H26Cl2N2O2
  • M r = 481.40
  • Triclinic, An external file that holds a picture, illustration, etc.
Object name is e-65-o3090-efi1.jpg
  • a = 10.1394 (6) Å
  • b = 10.7095 (6) Å
  • c = 12.2542 (4) Å
  • α = 82.084 (3)°
  • β = 71.403 (3)°
  • γ = 66.519 (2)°
  • V = 1156.66 (10) Å3
  • Z = 2
  • Mo Kα radiation
  • μ = 0.31 mm−1
  • T = 150 K
  • 0.20 × 0.12 × 0.10 mm

Data collection

  • Nonius KappaCCD diffractometer
  • Absorption correction: multi-scan from symmetry-related measurements (SORTAV; Blessing, 1995 [triangle]) T min = 0.670, T max = 0.974
  • 10842 measured reflections
  • 5170 independent reflections
  • 2859 reflections with I > 2σ(I)
  • R int = 0.067

Refinement

  • R[F 2 > 2σ(F 2)] = 0.064
  • wR(F 2) = 0.184
  • S = 1.02
  • 5170 reflections
  • 301 parameters
  • H-atom parameters constrained
  • Δρmax = 0.42 e Å−3
  • Δρmin = −0.30 e Å−3

Data collection: COLLECT (Nonius, 2002 [triangle]); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997 [triangle]); data reduction: DENZO-SMN; program(s) used to solve structure: SIR92 (Altomare et al., 1994 [triangle]); program(s) used to refine structure: SHELXTL (Sheldrick, 2008 [triangle]); molecular graphics: PLATON (Spek, 2009 [triangle]); software used to prepare material for publication: SHELXTL.

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809046765/pv2230sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809046765/pv2230Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

The authors are grateful for financial support from the American Chemical Society Petroleum Research Fund, the Dean’s Seed Fund Initiative (Ryerson University), NSERC Canada and the University of Toronto.

supplementary crystallographic information

Comment

The title compound was prepared by an intramolecular Buchwald-Hartwig reaction of the corresponding malonamide under conditions we have previously described (Porosa & Viirre, 2009) (Fig. 3). The intention in this reaction was to preferentially arylate one of the two enantiotopic nitrogen atoms in the malonamide by exploiting the chiral influence of (R)-MOP ((R)-(+)-2-(diphenylphosphino)-2'-methoxy-1,1'-binaphthyl) as a catalyst component. Indeed, chiral HPLC analysis of the product indicated the highest enantioselectivity we have yet observed in this reaction, at 96% ee. It was hoped that the configuration of the major enantiomer could be determined from a crystal structure in order to correlate product and catalyst configuration and aid in the development of a mechanistic model for the reaction. The initially isolated product with 96% ee was a very viscous yellow oil. This was dissolved in diethyl ether and left to stand undisturbed at room temperature for several days. Upon evaporation of most of the solvent, a yellow oil was again obtained, but dispersed within it were small clear crystals. One of the single crystals was subjected to X-ray diffraction analysis and the crystal structure is reported herein.

The molecular structure of the title compound is shown in Fig. 1. To our surprise, it crystallized in a centrosymmetric space group. As there is no apparent mechanism by which the quaternary chiral center can epimerize, this demonstrates an impressive propensity for the racemate (essentially a 4% impurity in the initial product) to crystallize in preference to enantiopure material. In the title molecule, the C13—C18 and C21—C26 benzene rings form dihedral angles of 83.29 (9) and 80.81 (9)°, respectively with the C4—C9 benzene ring. The dihedral angle formed by the C13—C18 and C21—C26 benzene rings is 40.87 (12) °. The C1—C4/C9/N1 ring is in a half-chair conformation. In the crystal structure, intermolecular N—H···O hydrogen bonds link molecules into centrosymmetric dimers (Fig. 2).

Work is currently underway to crystallize enantiopure material.

Experimental

The compound was prepared using the procedure previously described (Porosa & Viirre, 2009), using 2-(2-bromobenzyl)-N,N'-bis(4-chloro-2-methylbenzyl)-2-methylpropanediamide as a starting material. This material was recrystallized from diethylether to obtain small amounts of diffraction quality crystals of the title compound.

Refinement

H atoms were placed in calculated positions with C—H distances in the range 0.95–0.99 Å; N—H = 0.88Å and included in the refinement in the riding-model approximation with Uiso(H) = 1.2Ueq(C,N) or Uiso(H) = 1.5Ueq(C) for methyl H atoms.

Figures

Fig. 1.
The molecular structure showing 30% probability displacement ellipsoids (arbitrary spheres for H atoms).
Fig. 2.
Part of the crystal structure showing hydrogen bonds as dashed lines.
Fig. 3.
Reaction scheme.

Crystal data

C27H26Cl2N2O2Z = 2
Mr = 481.40F(000) = 504
Triclinic, P1Dx = 1.382 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 10.1394 (6) ÅCell parameters from 10842 reflections
b = 10.7095 (6) Åθ = 2.6–27.5°
c = 12.2542 (4) ŵ = 0.31 mm1
α = 82.084 (3)°T = 150 K
β = 71.403 (3)°Block, colourless
γ = 66.519 (2)°0.20 × 0.12 × 0.10 mm
V = 1156.66 (10) Å3

Data collection

Nonius KappaCCD diffractometer5170 independent reflections
Radiation source: fine-focus sealed tube2859 reflections with I > 2σ(I)
graphiteRint = 0.067
Detector resolution: 9 pixels mm-1θmax = 27.5°, θmin = 2.6°
[var phi] scans and ω scans with κ offsetsh = −12→13
Absorption correction: multi-scan from symmetry-related measurements (SORTAV; Blessing, 1995)k = −13→13
Tmin = 0.670, Tmax = 0.974l = −15→15
10842 measured reflections

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.064Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.184H-atom parameters constrained
S = 1.02w = 1/[σ2(Fo2) + (0.0886P)2 + 0.0727P] where P = (Fo2 + 2Fc2)/3
5170 reflections(Δ/σ)max = 0.001
301 parametersΔρmax = 0.42 e Å3
0 restraintsΔρmin = −0.30 e Å3

Special details

Experimental. 1H NMR [400 MHz, CDCl3] δH 7.31–6.94 (m, 8H), 6.78 (dd, J = 2 Hz, J = 8 Hz, 1H), 6.63 (dd, J = 8 Hz, J = 14 Hz, 2H), 5.07–4.91 (m, 2H), 4.35 (d, J = 6 Hz, 2H), 3.52 (d, J = 16 Hz, 1H), 3.09 (d, J = 16 Hz, 1H), 2.36 (s, 3H), 2.15 (s, 3H), 1.57 (s, 3H). HRMS (EI-TOF) calculated for C27H27N2O2 (M + H)+ 481.1450; observed 481.1426. HPLC (Chiralcel OD—H column, eluting with 0.65 ml/min 10% i-PrOH:hexanes), tR minor = 20.8 min (peak area = 181909), tR major = 24.5 min (peak area = 9489431), enantiomer ratio = 98:2, 96% ee.
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

xyzUiso*/Ueq
Cl10.21891 (11)0.99149 (9)1.07942 (7)0.0631 (3)
Cl20.43748 (10)0.28380 (10)−0.14948 (6)0.0707 (3)
O10.4463 (2)0.5129 (2)0.39762 (16)0.0514 (6)
O20.0270 (2)0.8179 (2)0.61445 (16)0.0507 (6)
N10.2188 (3)0.5470 (2)0.37995 (18)0.0405 (6)
N20.2249 (3)0.6438 (2)0.65164 (18)0.0424 (6)
H1N0.31720.58530.62350.051*
C10.3161 (4)0.5882 (3)0.4071 (2)0.0408 (7)
C20.2518 (3)0.7334 (3)0.4536 (2)0.0405 (7)
C30.1526 (3)0.8275 (3)0.3812 (2)0.0430 (7)
H3A0.10130.91950.41520.052*
H3B0.21670.83510.30250.052*
C40.0378 (3)0.7782 (3)0.3742 (2)0.0411 (7)
C5−0.1028 (4)0.8655 (3)0.3656 (2)0.0497 (8)
H5A−0.12860.96110.36590.060*
C6−0.2068 (4)0.8164 (4)0.3567 (2)0.0548 (9)
H6A−0.30290.87790.35160.066*
C7−0.1698 (4)0.6789 (4)0.3551 (2)0.0474 (8)
H7A−0.24050.64530.34820.057*
C8−0.0307 (4)0.5881 (3)0.3635 (2)0.0453 (8)
H8A−0.00580.49280.36190.054*
C90.0724 (3)0.6375 (3)0.3742 (2)0.0392 (7)
C100.3780 (3)0.7793 (3)0.4494 (2)0.0474 (8)
H10A0.33470.86970.48360.071*
H10B0.43700.78340.36920.071*
H10C0.44330.71430.49280.071*
C110.1555 (3)0.7353 (3)0.5808 (2)0.0411 (7)
C120.1485 (4)0.6406 (3)0.7743 (2)0.0430 (7)
H12A0.18700.54580.80290.052*
H12B0.04000.66700.78440.052*
C130.1659 (3)0.7323 (3)0.8486 (2)0.0391 (7)
C140.2568 (3)0.8058 (3)0.8039 (2)0.0436 (8)
H14A0.30980.79960.72420.052*
C150.2724 (4)0.8887 (3)0.8728 (3)0.0475 (8)
H15A0.33250.94130.84070.057*
C160.1988 (4)0.8925 (3)0.9887 (3)0.0448 (8)
C170.1071 (4)0.8214 (3)1.0353 (2)0.0443 (8)
H17A0.05650.82651.11550.053*
C180.0882 (3)0.7424 (3)0.9662 (2)0.0409 (7)
C19−0.0146 (4)0.6665 (4)1.0202 (3)0.0611 (10)
H19A−0.07700.70291.09690.092*
H19B0.04570.56961.02700.092*
H19C−0.07930.67770.97190.092*
C200.2704 (4)0.4028 (3)0.3528 (2)0.0426 (7)
H20A0.19030.36870.39570.051*
H20B0.35960.35060.38010.051*
C210.3107 (3)0.3756 (3)0.2262 (2)0.0353 (7)
C220.3173 (3)0.4763 (3)0.1428 (2)0.0443 (8)
H22A0.29430.56570.16550.053*
C230.3568 (3)0.4491 (3)0.0266 (2)0.0454 (8)
H23A0.36130.5185−0.03010.055*
C240.3888 (3)0.3208 (3)−0.0038 (2)0.0441 (8)
C250.3860 (3)0.2177 (3)0.0767 (2)0.0454 (8)
H25A0.41170.12840.05230.054*
C260.3458 (3)0.2435 (3)0.1934 (2)0.0387 (7)
C270.3438 (4)0.1298 (3)0.2814 (3)0.0522 (8)
H27A0.38000.04370.24170.078*
H27B0.24090.14960.33140.078*
H27C0.40920.12240.32800.078*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Cl10.0762 (7)0.0576 (6)0.0658 (5)−0.0194 (5)−0.0375 (5)−0.0109 (4)
Cl20.0653 (6)0.0933 (7)0.0363 (4)−0.0069 (5)−0.0133 (4)−0.0228 (4)
O10.0427 (14)0.0520 (14)0.0461 (12)0.0041 (11)−0.0187 (10)−0.0131 (10)
O20.0403 (13)0.0555 (14)0.0385 (11)−0.0003 (11)−0.0087 (9)−0.0066 (9)
N10.0423 (15)0.0379 (14)0.0337 (12)−0.0024 (12)−0.0141 (11)−0.0091 (10)
N20.0396 (14)0.0446 (15)0.0334 (12)−0.0037 (12)−0.0110 (10)−0.0071 (10)
C10.045 (2)0.0413 (18)0.0271 (14)−0.0046 (16)−0.0121 (13)−0.0058 (12)
C20.0418 (18)0.0402 (17)0.0308 (14)−0.0047 (14)−0.0098 (12)−0.0083 (12)
C30.0456 (19)0.0413 (18)0.0332 (15)−0.0070 (15)−0.0096 (13)−0.0066 (12)
C40.0429 (19)0.0440 (19)0.0269 (14)−0.0046 (15)−0.0116 (12)−0.0037 (12)
C50.051 (2)0.0443 (19)0.0386 (16)0.0018 (16)−0.0163 (14)−0.0055 (13)
C60.0394 (19)0.074 (3)0.0366 (16)−0.0004 (18)−0.0167 (14)−0.0091 (15)
C70.044 (2)0.061 (2)0.0354 (15)−0.0155 (18)−0.0116 (13)−0.0064 (14)
C80.050 (2)0.050 (2)0.0308 (14)−0.0141 (17)−0.0097 (13)−0.0054 (12)
C90.0388 (18)0.0443 (19)0.0255 (13)−0.0053 (15)−0.0083 (12)−0.0069 (12)
C100.0461 (19)0.053 (2)0.0396 (16)−0.0152 (16)−0.0089 (13)−0.0086 (13)
C110.0432 (19)0.0417 (18)0.0369 (15)−0.0083 (15)−0.0149 (13)−0.0115 (13)
C120.0493 (19)0.0435 (18)0.0362 (15)−0.0140 (15)−0.0160 (13)−0.0026 (12)
C130.0329 (17)0.0429 (17)0.0357 (15)−0.0049 (14)−0.0137 (12)−0.0021 (12)
C140.0375 (18)0.053 (2)0.0361 (15)−0.0120 (16)−0.0111 (13)−0.0019 (13)
C150.0445 (19)0.054 (2)0.0483 (18)−0.0209 (16)−0.0182 (14)0.0041 (14)
C160.0471 (19)0.0397 (18)0.0481 (17)−0.0055 (16)−0.0259 (15)−0.0072 (13)
C170.051 (2)0.0436 (18)0.0330 (15)−0.0102 (16)−0.0142 (13)−0.0029 (13)
C180.0430 (18)0.0399 (18)0.0361 (15)−0.0122 (15)−0.0124 (13)0.0027 (12)
C190.074 (3)0.075 (3)0.0436 (18)−0.039 (2)−0.0172 (16)0.0029 (16)
C200.0511 (19)0.0363 (17)0.0345 (14)−0.0058 (15)−0.0161 (13)−0.0062 (12)
C210.0289 (16)0.0395 (17)0.0326 (14)−0.0075 (13)−0.0088 (11)−0.0022 (12)
C220.0501 (19)0.0404 (18)0.0349 (15)−0.0083 (15)−0.0110 (13)−0.0076 (13)
C230.0410 (18)0.054 (2)0.0331 (15)−0.0115 (16)−0.0091 (13)0.0000 (13)
C240.0327 (17)0.059 (2)0.0344 (15)−0.0081 (15)−0.0097 (12)−0.0116 (14)
C250.0397 (18)0.0457 (19)0.0499 (18)−0.0116 (15)−0.0105 (14)−0.0184 (14)
C260.0295 (16)0.0445 (19)0.0399 (15)−0.0111 (14)−0.0069 (12)−0.0098 (13)
C270.056 (2)0.0424 (19)0.0528 (19)−0.0165 (17)−0.0097 (15)−0.0045 (14)

Geometric parameters (Å, °)

Cl1—C161.744 (3)C12—H12A0.9900
Cl2—C241.750 (3)C12—H12B0.9900
O1—C11.219 (3)C13—C141.381 (4)
O2—C111.220 (3)C13—C181.400 (4)
N1—C11.369 (4)C14—C151.389 (4)
N1—C91.432 (4)C14—H14A0.9500
N1—C201.468 (4)C15—C161.375 (4)
N2—C111.347 (4)C15—H15A0.9500
N2—C121.458 (3)C16—C171.370 (4)
N2—H1N0.8800C17—C181.379 (4)
C1—C21.539 (4)C17—H17A0.9500
C2—C31.526 (4)C18—C191.507 (4)
C2—C101.528 (4)C19—H19A0.9800
C2—C111.551 (4)C19—H19B0.9800
C3—C41.486 (4)C19—H19C0.9800
C3—H3A0.9900C20—C211.511 (3)
C3—H3B0.9900C20—H20A0.9900
C4—C51.387 (4)C20—H20B0.9900
C4—C91.404 (4)C21—C221.387 (4)
C5—C61.390 (5)C21—C261.398 (4)
C5—H5A0.9500C22—C231.389 (4)
C6—C71.369 (5)C22—H22A0.9500
C6—H6A0.9500C23—C241.357 (4)
C7—C81.385 (4)C23—H23A0.9500
C7—H7A0.9500C24—C251.379 (4)
C8—C91.392 (4)C25—C261.390 (4)
C8—H8A0.9500C25—H25A0.9500
C10—H10A0.9800C26—C271.513 (4)
C10—H10B0.9800C27—H27A0.9800
C10—H10C0.9800C27—H27B0.9800
C12—C131.519 (4)C27—H27C0.9800
C1—N1—C9123.4 (2)C14—C13—C18118.7 (3)
C1—N1—C20117.6 (2)C14—C13—C12122.1 (2)
C9—N1—C20119.0 (2)C18—C13—C12119.2 (3)
C11—N2—C12120.7 (2)C13—C14—C15121.5 (3)
C11—N2—H1N119.7C13—C14—H14A119.2
C12—N2—H1N119.7C15—C14—H14A119.2
O1—C1—N1121.9 (3)C16—C15—C14118.3 (3)
O1—C1—C2121.4 (3)C16—C15—H15A120.9
N1—C1—C2116.6 (3)C14—C15—H15A120.9
C3—C2—C10111.2 (2)C17—C16—C15121.5 (3)
C3—C2—C1108.0 (2)C17—C16—Cl1118.5 (2)
C10—C2—C1110.8 (2)C15—C16—Cl1120.0 (3)
C3—C2—C11109.5 (2)C16—C17—C18120.1 (3)
C10—C2—C11108.2 (2)C16—C17—H17A119.9
C1—C2—C11109.1 (2)C18—C17—H17A119.9
C4—C3—C2112.5 (2)C17—C18—C13119.8 (3)
C4—C3—H3A109.1C17—C18—C19118.7 (3)
C2—C3—H3A109.1C13—C18—C19121.5 (3)
C4—C3—H3B109.1C18—C19—H19A109.5
C2—C3—H3B109.1C18—C19—H19B109.5
H3A—C3—H3B107.8H19A—C19—H19B109.5
C5—C4—C9118.0 (3)C18—C19—H19C109.5
C5—C4—C3122.7 (3)H19A—C19—H19C109.5
C9—C4—C3119.3 (3)H19B—C19—H19C109.5
C4—C5—C6121.5 (3)N1—C20—C21114.2 (2)
C4—C5—H5A119.3N1—C20—H20A108.7
C6—C5—H5A119.3C21—C20—H20A108.7
C7—C6—C5119.5 (3)N1—C20—H20B108.7
C7—C6—H6A120.2C21—C20—H20B108.7
C5—C6—H6A120.2H20A—C20—H20B107.6
C6—C7—C8120.9 (3)C22—C21—C26119.7 (2)
C6—C7—H7A119.6C22—C21—C20122.0 (3)
C8—C7—H7A119.6C26—C21—C20118.3 (2)
C7—C8—C9119.4 (3)C21—C22—C23121.3 (3)
C7—C8—H8A120.3C21—C22—H22A119.4
C9—C8—H8A120.3C23—C22—H22A119.4
C8—C9—C4120.7 (3)C24—C23—C22118.3 (3)
C8—C9—N1121.1 (3)C24—C23—H23A120.8
C4—C9—N1118.2 (3)C22—C23—H23A120.8
C2—C10—H10A109.5C23—C24—C25121.9 (3)
C2—C10—H10B109.5C23—C24—Cl2119.3 (2)
H10A—C10—H10B109.5C25—C24—Cl2118.8 (2)
C2—C10—H10C109.5C24—C25—C26120.5 (3)
H10A—C10—H10C109.5C24—C25—H25A119.8
H10B—C10—H10C109.5C26—C25—H25A119.8
O2—C11—N2122.7 (3)C25—C26—C21118.3 (3)
O2—C11—C2121.6 (3)C25—C26—C27120.3 (3)
N2—C11—C2115.6 (2)C21—C26—C27121.4 (2)
N2—C12—C13115.5 (2)C26—C27—H27A109.5
N2—C12—H12A108.4C26—C27—H27B109.5
C13—C12—H12A108.4H27A—C27—H27B109.5
N2—C12—H12B108.4C26—C27—H27C109.5
C13—C12—H12B108.4H27A—C27—H27C109.5
H12A—C12—H12B107.5H27B—C27—H27C109.5

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
N2—H1N···O1i0.882.142.972 (3)157

Symmetry codes: (i) −x+1, −y+1, −z+1.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: PV2230).

References

  • Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994). J. Appl. Cryst. 27, 435.
  • Blessing, R. H. (1995). Acta Cryst. A51, 33–38. [PubMed]
  • Nonius (2002). COLLECT. Nonius BV, Delft, The Netherlands.
  • Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307–326. New York: Academic Press.
  • Porosa, L. & Viirre, R. D. (2009). Tetrahedron Lett. 50, 4170–4173.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Spek, A. L. (2009). Acta Cryst. D65, 148–155. [PMC free article] [PubMed]
  • Wang, X.-S., Zhang, M.-M., Zeng, Z.-S., Shi, D.-Q., Tu, S.-J., Wei, X.-Y. & Zong, Z.-M. (2007). J. Heterocycl. Chem. 44, 441–447.

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