organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890

6-Amino-4-(4-chloro­phen­yl)-2-oxo-1,2-di­hydro­pyridine-3,5-dicarbo­nitrile ethanol solvate

aLianyungang Teacher's College, Lianyungang 222006, People's Republic of China, and bCollege of Chemistry and Chemical Engineering, Xuzhou Normal University, Xuzhou 221116, People's Republic of China
*Correspondence e-mail: jiarunhong@126.com

(Received 11 May 2008; accepted 18 July 2008; online 23 July 2008)

The title compound, C13H7ClN4O·C2H6O, was synthesized by the reaction of 4-chloro­benzaldehyde, malononitrile and 10% sodium hydroxide solution in an aqueous medium. In the crystal structure, the crystal packing is stabilized by inter­molecular N—H⋯N, O—H⋯O and N—H⋯O hydrogen bonds.

Related literature

For related literature, see: Hasvold et al. (2003[Hasvold, L. A., Wang, W., Gwaltney, S. L., Rockway, T. W., Nelson, L. T. J., Mantei, R. A., Fakhoury, S. A., Sullivan, G. M., Li, Q., Lin, N.-H., Wang, L., Zhang, H., Cohen, J.; Gu, W.-Z., Marsh, K., Bauch, J., Rosenberg, S. & Sham, H. L. (2003). Bioorg. Med. Chem. Lett. 13, 4001-4005.]); Kappe (2004[Kappe, C. O. (2004). Angew. Chem. Int. Ed. 43, 6250-6284.]); Li et al. (2000[Li, Q., Mitscher, L. A. & Shen, L. L. (2000). Med. Res. Rev. 20, 231-293.]); Mederski et al. (1999[Mederski, W. W. K. R., Lefort, M., Germann, M. & Kux, D. (1999). Tetrahedron, 55, 12757-12770.]); Parlow et al. (2003[Parlow, J. J., Kurumbail, R. G., Stegeman, R. A., Stevens, A. M., Stallings, W. C. & South, M. S. (2003). J. Med. Chem. 46, 4696-4701.]); Varma (1999[Varma, R. S. (1999). J. Heterocycl. Chem. 36, 1565-1571.]).

[Scheme 1]

Experimental

Crystal data
  • C13H7ClN4O·C2H6O

  • Mr = 316.74

  • Triclinic, [P \overline 1]

  • a = 6.7787 (10) Å

  • b = 10.4318 (14) Å

  • c = 11.2857 (17) Å

  • α = 88.634 (2)°

  • β = 84.643 (1)°

  • γ = 81.700 (1)°

  • V = 786.2 (2) Å3

  • Z = 2

  • Mo Kα radiation

  • μ = 0.26 mm−1

  • T = 298 (2) K

  • 0.14 × 0.09 × 0.03 mm

Data collection
  • Bruker SMART CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.]) Tmin = 0.965, Tmax = 0.992

  • 4165 measured reflections

  • 2727 independent reflections

  • 1162 reflections with I > 2σ(I)

  • Rint = 0.033

Refinement
  • R[F2 > 2σ(F2)] = 0.056

  • wR(F2) = 0.140

  • S = 1.01

  • 2727 reflections

  • 199 parameters

  • H-atom parameters constrained

  • Δρmax = 0.31 e Å−3

  • Δρmin = −0.24 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O2—H2⋯O1i 0.82 2.02 2.755 (4) 149
N2—H2B⋯N3ii 0.86 2.25 3.084 (5) 164
N2—H2A⋯O2iii 0.86 1.98 2.832 (4) 168
N1—H1⋯O1iv 0.86 2.00 2.849 (4) 171
Symmetry codes: (i) -x, -y, -z+1; (ii) -x+2, -y+1, -z+1; (iii) x+1, y, z; (iv) -x+1, -y, -z+1.

Data collection: SMART (Bruker, 1998[Bruker (1998). SMART. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SMART; data reduction: SAINT (Bruker, 1999[Bruker (1999). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); software used to prepare material for publication: SHELXTL.

Supporting information


Comment top

In recent years, amino-substituted 2-pyridones have attracted attention due to their promising features as an important core structure for the development of biologically active molecules (Kappe, 2004). Pharmaceuticals with the 2- pyridone skeleton have emerged as antitumor (Varma, 1999), antifungal (Parlow et al.,2003), antibacterial (Hasvold et al. 2003), antiviral, antithrombotic (Li et al. 2000) agents. Meanwhile it is well known that the 2-pyridone ring system is a valuable building block in natural product synthesis. On the other hand, pyridine dicarbonitriles have been exhibited as potential novel prion disease therapeutics (Mederski et al. 1999). Therefore design and synthesis of these compounds has been challenging. For these reasons, the synthesis of compounds containing cyanopyridine derivatives is strongly desired. In this paper we report the crystal structure of the title compound, (I).

In the crystal structure, the dihedral angle between the C1/C2/C3/C4/C5/N1 plane and the C8—C13 benzene ring is 51.68 (13)° (Fig 1.). The molecules are connected via N—H···N and N—H···O intermolecular hydrogen bonds, forming a three-dimensional network (Table 1 and Fig. 2).

Related literature top

For related literature, see: Hasvold et al. (2003); Kappe (2004); Li et al. (2000); Mederski et al. (1999); Parlow et al. (2003); Varma (1999).

Experimental top

Compound (I) was prepared by the reaction of 4-chlorobenzaldehyde (1 mmol), malononitrile (2 mmol), 10% sodium hydroxide solution (1 ml) in water (2 ml). Single crystals of (I) suitable for X-ray diffraction were obtained by slow evaporation of a 95% aqueous ethanol solution (yield 48%; m.p. >573 K). IR (cm-1): 3450, 3317, 3205, 2216, 1669, 1590, 1484, 1378; 1H NMR (DMSO-d6): 7.53 (2H, d, J = 8.4 Hz, ArH), 7.64 (2H, d, J = 8.4 Hz, ArH), 7.72 (2H, brs, NH2), 11.94 (1H, s, NH).

Refinement top

All H atoms were positioned geometrically and treated as riding, with N—H = 0.86 Å, O–H = 0.82Å and C—H = 0.93–0.97 Å.

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SMART (Bruker, 1998); data reduction: SAINT (Bruker, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of title compound, showing 30% probability displacement ellipsoids.
[Figure 2] Fig. 2. The packing diagram of title compound viewed along the a axis.
6-Amino-4-(4-chlorophenyl)-2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile ethanol solvate top
Crystal data top
C13H7ClN4O·C2H6OZ = 2
Mr = 316.74F(000) = 328
Triclinic, P1Dx = 1.338 Mg m3
a = 6.7787 (10) ÅMo Kα radiation, λ = 0.71073 Å
b = 10.4318 (14) ÅCell parameters from 566 reflections
c = 11.2857 (17) Åθ = 2.7–20.3°
α = 88.634 (2)°µ = 0.26 mm1
β = 84.643 (1)°T = 298 K
γ = 81.700 (1)°Block, colorless
V = 786.2 (2) Å30.14 × 0.09 × 0.03 mm
Data collection top
Bruker SMART CCD area-detector
diffractometer
2727 independent reflections
Radiation source: fine-focus sealed tube1162 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.033
ϕ and ω scansθmax = 25.0°, θmin = 2.0°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 87
Tmin = 0.965, Tmax = 0.992k = 712
4165 measured reflectionsl = 1311
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.056Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.140H-atom parameters constrained
S = 1.01 w = 1/[σ2(Fo2) + (0.0453P)2 + 0.0621P]
where P = (Fo2 + 2Fc2)/3
2727 reflections(Δ/σ)max < 0.001
199 parametersΔρmax = 0.31 e Å3
0 restraintsΔρmin = 0.24 e Å3
Crystal data top
C13H7ClN4O·C2H6Oγ = 81.700 (1)°
Mr = 316.74V = 786.2 (2) Å3
Triclinic, P1Z = 2
a = 6.7787 (10) ÅMo Kα radiation
b = 10.4318 (14) ŵ = 0.26 mm1
c = 11.2857 (17) ÅT = 298 K
α = 88.634 (2)°0.14 × 0.09 × 0.03 mm
β = 84.643 (1)°
Data collection top
Bruker SMART CCD area-detector
diffractometer
2727 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
1162 reflections with I > 2σ(I)
Tmin = 0.965, Tmax = 0.992Rint = 0.033
4165 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0560 restraints
wR(F2) = 0.140H-atom parameters constrained
S = 1.01Δρmax = 0.31 e Å3
2727 reflectionsΔρmin = 0.24 e Å3
199 parameters
Special details top

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) top
xyzUiso*/Ueq
Cl10.3974 (2)0.82840 (13)0.02206 (12)0.0905 (6)
N10.5949 (5)0.1640 (3)0.4620 (3)0.0420 (9)
H10.62640.09640.50510.050*
N20.8641 (5)0.2447 (3)0.5286 (3)0.0520 (10)
H2A0.88770.17480.57000.062*
H2B0.93980.30400.53040.062*
N30.8433 (5)0.5684 (4)0.4171 (3)0.0565 (11)
N40.0902 (6)0.2779 (4)0.1960 (3)0.0705 (13)
O10.3337 (4)0.0727 (3)0.4075 (2)0.0544 (9)
O20.0003 (5)0.0195 (3)0.6598 (3)0.0923 (13)
H20.09270.02370.66390.138*
C10.7115 (6)0.2611 (4)0.4621 (3)0.0389 (11)
C20.6615 (5)0.3715 (4)0.3915 (3)0.0353 (10)
C30.5067 (6)0.3773 (4)0.3158 (3)0.0376 (10)
C40.3897 (6)0.2774 (4)0.3224 (3)0.0389 (11)
C50.4310 (6)0.1666 (4)0.3979 (3)0.0405 (11)
C60.7651 (6)0.4800 (4)0.4034 (3)0.0422 (11)
C70.2249 (6)0.2769 (4)0.2514 (4)0.0473 (12)
C80.4755 (6)0.4877 (4)0.2317 (3)0.0389 (10)
C90.2890 (6)0.5612 (4)0.2250 (4)0.0526 (12)
H90.17890.54060.27330.063*
C100.2668 (7)0.6653 (5)0.1464 (4)0.0615 (14)
H100.14160.71450.14270.074*
C110.4283 (8)0.6966 (4)0.0736 (4)0.0576 (13)
C120.6122 (7)0.6221 (4)0.0768 (4)0.0494 (12)
H120.72020.64120.02590.059*
C130.6369 (6)0.5191 (4)0.1552 (3)0.0425 (11)
H130.76220.46970.15740.051*
C140.0839 (8)0.0126 (5)0.7684 (4)0.0776 (16)
H14A0.14640.07530.78280.093*
H14B0.02000.03590.83240.093*
C150.2369 (8)0.1030 (5)0.7664 (5)0.0884 (18)
H15A0.29410.09800.84130.133*
H15B0.17430.19000.75280.133*
H15C0.34040.07880.70370.133*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cl10.1212 (13)0.0645 (10)0.0815 (10)0.0005 (8)0.0159 (8)0.0352 (8)
N10.050 (2)0.032 (2)0.049 (2)0.0153 (18)0.0145 (17)0.0133 (18)
N20.058 (2)0.041 (2)0.065 (2)0.0234 (19)0.025 (2)0.015 (2)
N30.064 (3)0.056 (3)0.057 (2)0.028 (2)0.016 (2)0.010 (2)
N40.063 (3)0.068 (3)0.088 (3)0.025 (2)0.031 (2)0.018 (3)
O10.0521 (19)0.047 (2)0.074 (2)0.0301 (16)0.0224 (16)0.0188 (17)
O20.097 (3)0.081 (3)0.119 (3)0.050 (2)0.067 (2)0.045 (2)
C10.043 (3)0.036 (3)0.041 (2)0.011 (2)0.011 (2)0.004 (2)
C20.041 (3)0.031 (3)0.037 (2)0.014 (2)0.0074 (19)0.004 (2)
C30.041 (3)0.034 (3)0.038 (2)0.011 (2)0.000 (2)0.004 (2)
C40.038 (2)0.040 (3)0.042 (2)0.014 (2)0.008 (2)0.008 (2)
C50.038 (3)0.040 (3)0.045 (3)0.007 (2)0.009 (2)0.008 (2)
C60.047 (3)0.041 (3)0.041 (3)0.013 (2)0.006 (2)0.007 (2)
C70.046 (3)0.043 (3)0.055 (3)0.015 (2)0.008 (2)0.013 (2)
C80.040 (3)0.034 (3)0.045 (3)0.014 (2)0.005 (2)0.007 (2)
C90.052 (3)0.040 (3)0.065 (3)0.005 (2)0.004 (2)0.009 (3)
C100.052 (3)0.050 (3)0.077 (4)0.006 (3)0.005 (3)0.009 (3)
C110.072 (4)0.045 (3)0.057 (3)0.004 (3)0.018 (3)0.016 (3)
C120.064 (3)0.046 (3)0.042 (3)0.023 (3)0.010 (2)0.012 (2)
C130.043 (3)0.042 (3)0.045 (3)0.012 (2)0.010 (2)0.008 (2)
C140.103 (4)0.058 (4)0.078 (4)0.023 (3)0.027 (3)0.010 (3)
C150.085 (4)0.074 (4)0.115 (5)0.020 (3)0.036 (3)0.014 (4)
Geometric parameters (Å, º) top
Cl1—C111.728 (4)C4—C71.435 (5)
N1—C11.372 (4)C8—C91.388 (5)
N1—C51.377 (4)C8—C131.401 (5)
N1—H10.8600C9—C101.385 (5)
N2—C11.323 (4)C9—H90.9300
N2—H2A0.8600C10—C111.380 (6)
N2—H2B0.8600C10—H100.9300
N3—C61.147 (5)C11—C121.374 (6)
N4—C71.152 (5)C12—C131.377 (5)
O1—C51.255 (4)C12—H120.9300
O2—C141.396 (5)C13—H130.9300
O2—H20.8200C14—C151.497 (6)
C1—C21.404 (5)C14—H14A0.9700
C2—C31.407 (5)C14—H14B0.9700
C2—C61.432 (5)C15—H15A0.9600
C3—C41.395 (5)C15—H15B0.9600
C3—C81.479 (5)C15—H15C0.9600
C4—C51.429 (5)
C1—N1—C5124.9 (3)C10—C9—C8120.0 (4)
C1—N1—H1117.5C10—C9—H9120.0
C5—N1—H1117.5C8—C9—H9120.0
C1—N2—H2A120.0C11—C10—C9120.7 (4)
C1—N2—H2B120.0C11—C10—H10119.6
H2A—N2—H2B120.0C9—C10—H10119.6
C14—O2—H2109.5C12—C11—C10119.7 (4)
N2—C1—N1118.0 (4)C12—C11—Cl1120.5 (4)
N2—C1—C2124.1 (4)C10—C11—Cl1119.8 (4)
N1—C1—C2117.9 (4)C11—C12—C13120.2 (4)
C1—C2—C3120.7 (4)C11—C12—H12119.9
C1—C2—C6118.1 (3)C13—C12—H12119.9
C3—C2—C6121.1 (4)C12—C13—C8120.8 (4)
C4—C3—C2118.4 (4)C12—C13—H13119.6
C4—C3—C8122.5 (3)C8—C13—H13119.6
C2—C3—C8119.1 (4)O2—C14—C15109.8 (4)
C3—C4—C5121.8 (4)O2—C14—H14A109.7
C3—C4—C7122.4 (4)C15—C14—H14A109.7
C5—C4—C7115.7 (4)O2—C14—H14B109.7
O1—C5—N1118.8 (4)C15—C14—H14B109.7
O1—C5—C4125.3 (4)H14A—C14—H14B108.2
N1—C5—C4115.9 (4)C14—C15—H15A109.5
N3—C6—C2177.2 (5)C14—C15—H15B109.5
N4—C7—C4178.7 (5)H15A—C15—H15B109.5
C9—C8—C13118.5 (4)C14—C15—H15C109.5
C9—C8—C3121.9 (4)H15A—C15—H15C109.5
C13—C8—C3119.7 (4)H15B—C15—H15C109.5
C5—N1—C1—N2179.8 (4)C7—C4—C5—O11.2 (6)
C5—N1—C1—C20.3 (6)C3—C4—C5—N11.0 (6)
N2—C1—C2—C3174.8 (4)C7—C4—C5—N1177.1 (4)
N1—C1—C2—C35.0 (6)C4—C3—C8—C952.2 (6)
N2—C1—C2—C68.4 (6)C2—C3—C8—C9128.5 (4)
N1—C1—C2—C6171.8 (3)C4—C3—C8—C13127.0 (4)
C1—C2—C3—C47.1 (6)C2—C3—C8—C1352.4 (5)
C6—C2—C3—C4169.6 (4)C13—C8—C9—C101.9 (6)
C1—C2—C3—C8172.3 (4)C3—C8—C9—C10178.9 (4)
C6—C2—C3—C811.0 (6)C8—C9—C10—C110.4 (7)
C2—C3—C4—C54.0 (6)C9—C10—C11—C121.6 (7)
C8—C3—C4—C5175.4 (4)C9—C10—C11—Cl1179.0 (4)
C2—C3—C4—C7178.1 (4)C10—C11—C12—C132.2 (7)
C8—C3—C4—C72.5 (6)Cl1—C11—C12—C13178.5 (3)
C1—N1—C5—O1178.4 (4)C11—C12—C13—C80.7 (6)
C1—N1—C5—C43.3 (6)C9—C8—C13—C121.3 (6)
C3—C4—C5—O1179.2 (4)C3—C8—C13—C12179.5 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H2···O1i0.822.022.755 (4)149
N2—H2B···N3ii0.862.253.084 (5)164
N2—H2A···O2iii0.861.982.832 (4)168
N1—H1···O1iv0.862.002.849 (4)171
Symmetry codes: (i) x, y, z+1; (ii) x+2, y+1, z+1; (iii) x+1, y, z; (iv) x+1, y, z+1.

Experimental details

Crystal data
Chemical formulaC13H7ClN4O·C2H6O
Mr316.74
Crystal system, space groupTriclinic, P1
Temperature (K)298
a, b, c (Å)6.7787 (10), 10.4318 (14), 11.2857 (17)
α, β, γ (°)88.634 (2), 84.643 (1), 81.700 (1)
V3)786.2 (2)
Z2
Radiation typeMo Kα
µ (mm1)0.26
Crystal size (mm)0.14 × 0.09 × 0.03
Data collection
DiffractometerBruker SMART CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.965, 0.992
No. of measured, independent and
observed [I > 2σ(I)] reflections
4165, 2727, 1162
Rint0.033
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.056, 0.140, 1.01
No. of reflections2727
No. of parameters199
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.31, 0.24

Computer programs: SMART (Bruker, 1998), SAINT (Bruker, 1999), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H2···O1i0.822.022.755 (4)148.7
N2—H2B···N3ii0.862.253.084 (5)164.2
N2—H2A···O2iii0.861.982.832 (4)168.3
N1—H1···O1iv0.862.002.849 (4)170.8
Symmetry codes: (i) x, y, z+1; (ii) x+2, y+1, z+1; (iii) x+1, y, z; (iv) x+1, y, z+1.
 

Acknowledgements

The authors thank the National Natural Science Foundation of China (grant No. 20672090) and the Natural Science Foundation of Jiangsu Province (grant No. BK2006033) for financial support.

References

First citationBruker (1998). SMART. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationBruker (1999). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationHasvold, L. A., Wang, W., Gwaltney, S. L., Rockway, T. W., Nelson, L. T. J., Mantei, R. A., Fakhoury, S. A., Sullivan, G. M., Li, Q., Lin, N.-H., Wang, L., Zhang, H., Cohen, J.; Gu, W.-Z., Marsh, K., Bauch, J., Rosenberg, S. & Sham, H. L. (2003). Bioorg. Med. Chem. Lett. 13, 4001–4005.  Web of Science CrossRef PubMed CAS Google Scholar
First citationKappe, C. O. (2004). Angew. Chem. Int. Ed. 43, 6250–6284.  Web of Science CrossRef CAS Google Scholar
First citationLi, Q., Mitscher, L. A. & Shen, L. L. (2000). Med. Res. Rev. 20, 231–293.  Web of Science CrossRef PubMed CAS Google Scholar
First citationMederski, W. W. K. R., Lefort, M., Germann, M. & Kux, D. (1999). Tetrahedron, 55, 12757–12770.  Web of Science CrossRef CAS Google Scholar
First citationParlow, J. J., Kurumbail, R. G., Stegeman, R. A., Stevens, A. M., Stallings, W. C. & South, M. S. (2003). J. Med. Chem. 46, 4696–4701.  Web of Science CrossRef PubMed CAS Google Scholar
First citationSheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.  Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationVarma, R. S. (1999). J. Heterocycl. Chem. 36, 1565–1571.  CrossRef CAS Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Follow Acta Cryst. E
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds