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

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890

3-Ethyl-6-(4-fluoro­phen­yl)-7H-1,2,4-triazolo[3,4-b][1,3,4]thia­diazine

aDepartment of Physics, Yuvaraja's College (Constituent College), University of Mysore, Mysore 570 005, Karnataka, India, bSolid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 12, Karnataka, India, and cDepartment of Physics, St Philomena's College (Autonomous), Mysore 570 015, Karnataka, India
*Correspondence e-mail: devarajegowda@yahoo.com

(Received 12 May 2012; accepted 14 May 2012; online 23 May 2012)

In the title compound, C12H11FN4S, the thia­diazine ring adopts a twist-boat conformation. The dihedral angle between the triazolothia­diazine system and the benzene ring is 10.54 (9)°. The crystal structure is characterized by C—H⋯N hydrogen bonds. The crystal packing also exhibits ππ inter­actions, with a centroid–centroid distance of 3.6348 (15) Å.

Related literature

For biological properties of triazolothia­diazines, see: Feng et al. (1992[Feng, X. M., Chen, R. & Yang, W. D. (1992). Chem. J. Chin. Univ. 13, 187-194.]); Mohan & Anjaneyalu (1987[Mohan, J. & Anjaneyalu, G. S. R. (1987). Pol. J. Chem. 61, 547-551.]); Holla et al. (2001[Holla, B. S., Akberali, P. M. & Shivananda, M. K. (2001). Il Farmaco, 56, 919-927.]); Walser et al. (1991[Walser, A., Flynn, T. & Mason, C. (1991). J. Heterocycl. Chem. 28, 1121-1125.]); Hirota et al. (1991[Hirota, T., Sasaki, K., Yamamoto, H. & Nakayama, T. (1991). J. Heterocycl. Chem. 28, 257-261.]); Bradbury & Rivett (1991[Bradbury, R. H. & Rivett, J. E. (1991). J. Med. Chem. 34, 151-157.]); Heindel & Reid (1980[Heindel, N. D. & Reid, J. R. (1980). J. Heterocycl. Chem. 17, 1087-1088.]); Heidelberger et al. (1957[Heidelberger, C., Chaudhuri, N. K., Danneberg, P., Mooren, D., Greisbach, L., Duschinsky, R., Scnnitzer, R. J., Pleaven, E. & Scheiner, J. (1957). Nature (London), 179, 663-666.]). For related structures, see: Andersson & MacGowan (2003[Andersson, M. I. & MacGowan, A. P. (2003). J. Antimicrob. Chemother. 51, 1-11.]); Novak et al. (2006[Novak, M. J., Baum, J. C. & Buhrow, J. A. (2006). Olson. Surf. Sci. 600, L269-L273.]).

[Scheme 1]

Experimental

Crystal data
  • C12H11FN4S

  • Mr = 262.31

  • Monoclinic, P 21 /c

  • a = 13.322 (3) Å

  • b = 13.017 (3) Å

  • c = 7.1912 (16) Å

  • β = 105.308 (4)°

  • V = 1202.8 (4) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.27 mm−1

  • T = 293 K

  • 0.24 × 0.20 × 0.12 mm

Data collection
  • Bruker SMART CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2001[Bruker (2001). SMART, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.770, Tmax = 1.000

  • 11097 measured reflections

  • 2119 independent reflections

  • 1828 reflections with I > 2σ(I)

  • Rint = 0.023

Refinement
  • R[F2 > 2σ(F2)] = 0.041

  • wR(F2) = 0.106

  • S = 1.06

  • 2119 reflections

  • 164 parameters

  • H-atom parameters constrained

  • Δρmax = 0.22 e Å−3

  • Δρmin = −0.22 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C1—H1⋯N2i 0.93 2.51 3.428 (3) 172
C8—H8A⋯N1ii 0.97 2.50 3.410 (3) 156
C8—H8B⋯N2i 0.97 2.30 3.228 (3) 160
Symmetry codes: (i) [-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]; (ii) [x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}].

Data collection: SMART (Bruker, 2001[Bruker (2001). SMART, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2001[Bruker (2001). SMART, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; 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: ORTEP-3 (Farrugia, 1997[Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.]); software used to prepare material for publication: SHELXL97.

Supporting information


Comment top

Triazoles fused with six membered ring systems are found to be associated with diverse pharmacological activity. A number of thiadiazines have been shown to exhibit antimicrobial (Feng et al., 1992) and dieretic properties (Mohan et al., 1987) and also serves as photographic couplers (Holla et al., 2001). The analgesic, anti-asthmatic, diuretic, anti-hypertensive, anti-cholinergic, antibacterial, antifungal, anti-inflammatory, hypoglycemic, anti-tubercular and antiviral properties exhibited by various N-bridged heterocycles derived from a variety of 4-amino-5-mercapto-1,2,4-triazoles, have made them an important chemotherapeutic agents (Walser et al., 1991; Hirota et al., 1991; Bradbury et al., 1991). The 1,2,4- triazoles nucleus has recently been incorporated into a wide variety of therapeutically interesting drugs including H1/H2 histamine receptor blockers, cholinesterase active agents, CNS stimulants, anti-anxiety agents and sedatives (Heindel et al., 1980). Further fluorinated heterocycles have been shown to possess wide variety of biocidal activities. Compounds such as fluorouracil and fluoroquinolone have been used as anticancer agents and antibiotics (Heidelberger et al., 1957; Andersson et al., 2003; Novak et al., 2006).

The asymmetric unit of 3-ethyl-6-(4-fluorophenyl)-7H-[1,2,4]triazolo[3,4-b] [1,3,4]thiadiazine is shown in Fig. 1. The triazolo-thiadiazine ring system is not planar. The dihedral angle between the triazolo-thiadiazine ring system (S1/N1–N4/C7–C10) and the benzene ring (C1–C6) is 10.54 (9)°.

In the crystal structure (Fig. 2), the molecules are connected via intermolecular C1—H1···N2, C8—H8A···N1 and C8—H8B···N2 hydrogen bonds (Table 1). Furthermore, the crystal structure features a π-π interaction, with a centroid-centroid Cg1 (C9/C10/N1–N3) distance of 3.5728 (16) Å.

Related literature top

For biological properties of triazolothiadiazines, see: Feng et al. (1992); Mohan & Anjaneyalu (1987); Holla et al. (2001); Walser et al. (1991); Hirota et al. (1991); Bradbury & Rivett (1991); Heindel & Reid (1980); Heidelberger et al. (1957). For related structures, see: Andersson & MacGowan (2003); Novak et al. (2006).

Experimental top

A mixture of triazole (1) (0.01 mol) and p-fluorophenacyl bromide (0.01 mol) in ethanol (25 ml) was heated under reflux for 1–2 hrs. The reaction mixture was cooled to room temparature and neutralized with sodium acetate (5%). The precipitated triazolothiadiazines were collected by filtration, washed with water and recrystallized from ethanol. Yield 82%; m.p.455 K.

Refinement top

All H atoms were positioned geometrically, with C—H = 0.93 Å for aromatic H, C—H = 0.97 Å for methylene H and C—H = 0.96 Å for methyl H, and refined using a riding model with Uiso(H) = 1.5Ueq(C) for methyl H and Uiso(H) = 1.2Ueq(C) for all other H.

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 2] Fig. 2. The packing of molecules in the title structure.
3-Ethyl-6-(4-fluorophenyl)-7H-1,2,4- triazolo[3,4-b][1,3,4]thiadiazine top
Crystal data top
C12H11FN4SF(000) = 544
Mr = 262.31Dx = 1.449 Mg m3
Monoclinic, P21/cMelting point: 455 K
Hall symbol: -P 2ybcMo Kα radiation, λ = 0.71073 Å
a = 13.322 (3) ÅCell parameters from 2119 reflections
b = 13.017 (3) Åθ = 2.2–25.0°
c = 7.1912 (16) ŵ = 0.27 mm1
β = 105.308 (4)°T = 293 K
V = 1202.8 (4) Å3Plate, colourless
Z = 40.24 × 0.20 × 0.12 mm
Data collection top
Bruker SMART CCD area-detector
diffractometer
2119 independent reflections
Radiation source: fine-focus sealed tube1828 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.023
ω and ϕ scansθmax = 25.0°, θmin = 2.2°
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
h = 1515
Tmin = 0.770, Tmax = 1.000k = 1515
11097 measured reflectionsl = 88
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)] = 0.041Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.106H-atom parameters constrained
S = 1.06 w = 1/[σ2(Fo2) + (0.0487P)2 + 0.4632P]
where P = (Fo2 + 2Fc2)/3
2119 reflections(Δ/σ)max < 0.001
164 parametersΔρmax = 0.22 e Å3
0 restraintsΔρmin = 0.22 e Å3
Crystal data top
C12H11FN4SV = 1202.8 (4) Å3
Mr = 262.31Z = 4
Monoclinic, P21/cMo Kα radiation
a = 13.322 (3) ŵ = 0.27 mm1
b = 13.017 (3) ÅT = 293 K
c = 7.1912 (16) Å0.24 × 0.20 × 0.12 mm
β = 105.308 (4)°
Data collection top
Bruker SMART CCD area-detector
diffractometer
2119 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
1828 reflections with I > 2σ(I)
Tmin = 0.770, Tmax = 1.000Rint = 0.023
11097 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0410 restraints
wR(F2) = 0.106H-atom parameters constrained
S = 1.06Δρmax = 0.22 e Å3
2119 reflectionsΔρmin = 0.22 e Å3
164 parameters
Special details top

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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
S10.50854 (4)0.90687 (4)0.19250 (9)0.0542 (2)
F10.05432 (12)1.31988 (11)0.1252 (2)0.0845 (5)
N10.37247 (14)0.64191 (13)0.1417 (3)0.0511 (5)
N20.46299 (14)0.70215 (13)0.1828 (3)0.0550 (5)
N30.32718 (12)0.80332 (11)0.1211 (2)0.0397 (4)
N40.26399 (12)0.88834 (12)0.0605 (2)0.0403 (4)
C10.28158 (17)1.16575 (16)0.0713 (3)0.0534 (6)
H10.35261.17460.12560.064*
C20.21920 (19)1.25088 (18)0.0115 (4)0.0626 (6)
H20.24761.31660.02530.075*
C30.11625 (18)1.23664 (17)0.0673 (4)0.0566 (6)
C40.07182 (18)1.14193 (19)0.0911 (4)0.0625 (6)
H40.00081.13460.14640.075*
C50.13374 (16)1.05684 (17)0.0319 (3)0.0536 (6)
H50.10420.99160.04790.064*
C60.24016 (15)1.06767 (15)0.0515 (3)0.0407 (5)
C70.30545 (14)0.97569 (14)0.1164 (3)0.0378 (4)
C80.41148 (15)0.98739 (15)0.2543 (3)0.0446 (5)
H8A0.40730.97020.38330.054*
H8B0.43301.05860.25520.054*
C90.43346 (15)0.79735 (15)0.1685 (3)0.0436 (5)
C100.29301 (15)0.70301 (14)0.1038 (3)0.0423 (5)
C110.18178 (17)0.67302 (16)0.0591 (4)0.0547 (6)
H11A0.14310.71220.05140.066*
H11B0.15480.69070.16770.066*
C120.1639 (2)0.56042 (18)0.0163 (4)0.0671 (7)
H12A0.18190.54410.10110.101*
H12B0.09200.54430.00240.101*
H12C0.20660.52100.12040.101*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
S10.0360 (3)0.0450 (3)0.0800 (4)0.0006 (2)0.0126 (3)0.0070 (3)
F10.0731 (10)0.0583 (9)0.1191 (13)0.0317 (8)0.0204 (9)0.0218 (8)
N10.0518 (11)0.0354 (9)0.0640 (12)0.0038 (8)0.0113 (9)0.0002 (8)
N20.0464 (10)0.0411 (10)0.0745 (13)0.0081 (8)0.0108 (9)0.0033 (9)
N30.0371 (8)0.0311 (8)0.0479 (9)0.0031 (7)0.0060 (7)0.0004 (7)
N40.0357 (9)0.0329 (9)0.0489 (10)0.0036 (7)0.0053 (7)0.0006 (7)
C10.0437 (12)0.0385 (12)0.0739 (15)0.0028 (9)0.0084 (10)0.0023 (10)
C20.0622 (15)0.0361 (12)0.0880 (18)0.0041 (11)0.0175 (13)0.0021 (11)
C30.0581 (14)0.0450 (13)0.0682 (15)0.0194 (11)0.0194 (11)0.0112 (11)
C40.0413 (12)0.0615 (15)0.0780 (16)0.0107 (11)0.0039 (11)0.0074 (13)
C50.0426 (12)0.0425 (12)0.0702 (15)0.0008 (9)0.0049 (10)0.0036 (10)
C60.0404 (11)0.0367 (10)0.0443 (11)0.0030 (8)0.0099 (9)0.0008 (8)
C70.0364 (10)0.0350 (10)0.0414 (10)0.0004 (8)0.0091 (8)0.0005 (8)
C80.0394 (11)0.0332 (10)0.0550 (12)0.0019 (8)0.0013 (9)0.0002 (9)
C90.0383 (10)0.0400 (11)0.0511 (12)0.0050 (9)0.0091 (9)0.0035 (9)
C100.0483 (11)0.0312 (10)0.0446 (11)0.0006 (9)0.0071 (9)0.0015 (8)
C110.0498 (13)0.0416 (12)0.0682 (14)0.0055 (10)0.0075 (11)0.0017 (10)
C120.0722 (17)0.0486 (13)0.0808 (17)0.0161 (12)0.0210 (14)0.0076 (12)
Geometric parameters (Å, º) top
S1—C91.724 (2)C4—C51.379 (3)
S1—C81.809 (2)C4—H40.9300
F1—C31.359 (2)C5—C61.393 (3)
N1—C101.294 (2)C5—H50.9300
N1—N21.403 (2)C6—C71.481 (3)
N2—C91.296 (2)C7—C81.504 (3)
N3—C91.368 (3)C8—H8A0.9700
N3—C101.377 (2)C8—H8B0.9700
N3—N41.389 (2)C10—C111.483 (3)
N4—C71.282 (2)C11—C121.504 (3)
C1—C61.383 (3)C11—H11A0.9700
C1—C21.384 (3)C11—H11B0.9700
C1—H10.9300C12—H12A0.9600
C2—C31.351 (3)C12—H12B0.9600
C2—H20.9300C12—H12C0.9600
C3—C41.359 (3)
C9—S1—C894.03 (9)N4—C7—C8123.28 (17)
C10—N1—N2108.10 (16)C6—C7—C8119.81 (16)
C9—N2—N1106.96 (17)C7—C8—S1112.80 (14)
C9—N3—C10105.32 (16)C7—C8—H8A109.0
C9—N3—N4128.67 (16)S1—C8—H8A109.0
C10—N3—N4124.63 (15)C7—C8—H8B109.0
C7—N4—N3115.66 (15)S1—C8—H8B109.0
C6—C1—C2121.1 (2)H8A—C8—H8B107.8
C6—C1—H1119.4N2—C9—N3110.27 (17)
C2—C1—H1119.4N2—C9—S1128.82 (16)
C3—C2—C1118.7 (2)N3—C9—S1120.86 (14)
C3—C2—H2120.6N1—C10—N3109.33 (17)
C1—C2—H2120.6N1—C10—C11126.78 (18)
C2—C3—C4122.5 (2)N3—C10—C11123.81 (17)
C2—C3—F1119.1 (2)C10—C11—C12113.32 (19)
C4—C3—F1118.4 (2)C10—C11—H11A108.9
C3—C4—C5119.0 (2)C12—C11—H11A108.9
C3—C4—H4120.5C10—C11—H11B108.9
C5—C4—H4120.5C12—C11—H11B108.9
C4—C5—C6120.6 (2)H11A—C11—H11B107.7
C4—C5—H5119.7C11—C12—H12A109.5
C6—C5—H5119.7C11—C12—H12B109.5
C1—C6—C5118.08 (19)H12A—C12—H12B109.5
C1—C6—C7121.91 (18)C11—C12—H12C109.5
C5—C6—C7120.01 (18)H12A—C12—H12C109.5
N4—C7—C6116.73 (16)H12B—C12—H12C109.5
C10—N1—N2—C90.3 (2)N4—C7—C8—S146.9 (2)
C9—N3—N4—C726.4 (3)C6—C7—C8—S1138.27 (16)
C10—N3—N4—C7168.98 (18)C9—S1—C8—C749.59 (16)
C6—C1—C2—C30.1 (4)N1—N2—C9—N30.5 (2)
C1—C2—C3—C40.4 (4)N1—N2—C9—S1177.06 (16)
C1—C2—C3—F1179.6 (2)C10—N3—C9—N21.0 (2)
C2—C3—C4—C50.3 (4)N4—N3—C9—N2167.93 (18)
F1—C3—C4—C5179.7 (2)C10—N3—C9—S1176.72 (15)
C3—C4—C5—C60.2 (4)N4—N3—C9—S19.8 (3)
C2—C1—C6—C50.6 (3)C8—S1—C9—N2156.4 (2)
C2—C1—C6—C7179.4 (2)C8—S1—C9—N326.27 (18)
C4—C5—C6—C10.6 (3)N2—N1—C10—N31.0 (2)
C4—C5—C6—C7179.3 (2)N2—N1—C10—C11177.8 (2)
N3—N4—C7—C6179.22 (16)C9—N3—C10—N11.2 (2)
N3—N4—C7—C85.8 (3)N4—N3—C10—N1168.80 (17)
C1—C6—C7—N4167.62 (19)C9—N3—C10—C11178.14 (19)
C5—C6—C7—N412.5 (3)N4—N3—C10—C1114.3 (3)
C1—C6—C7—C817.2 (3)N1—C10—C11—C1213.0 (3)
C5—C6—C7—C8162.73 (19)N3—C10—C11—C12170.6 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C1—H1···N2i0.932.513.428 (3)172
C8—H8A···N1ii0.972.503.410 (3)156
C8—H8B···N2i0.972.303.228 (3)160
Symmetry codes: (i) x+1, y+1/2, z+1/2; (ii) x, y+3/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC12H11FN4S
Mr262.31
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)13.322 (3), 13.017 (3), 7.1912 (16)
β (°) 105.308 (4)
V3)1202.8 (4)
Z4
Radiation typeMo Kα
µ (mm1)0.27
Crystal size (mm)0.24 × 0.20 × 0.12
Data collection
DiffractometerBruker SMART CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2001)
Tmin, Tmax0.770, 1.000
No. of measured, independent and
observed [I > 2σ(I)] reflections
11097, 2119, 1828
Rint0.023
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.041, 0.106, 1.06
No. of reflections2119
No. of parameters164
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.22, 0.22

Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C1—H1···N2i0.932.513.428 (3)172
C8—H8A···N1ii0.972.503.410 (3)156
C8—H8B···N2i0.972.303.228 (3)160
Symmetry codes: (i) x+1, y+1/2, z+1/2; (ii) x, y+3/2, z+1/2.
 

Acknowledgements

The authors thank Professor T. N. Guru Row, Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, for the data collection. SJ thanks the University Grants Commission (India), for the award of a Teacher Fellowship under the Faculty Development Programme (UGC-SWRO File No.: FIP/11 th Plan/KAMY006 TF, Dt.: 06/08/2010).

References

First citationAndersson, M. I. & MacGowan, A. P. (2003). J. Antimicrob. Chemother. 51, 1–11.  Web of Science CrossRef PubMed CAS Google Scholar
First citationBradbury, R. H. & Rivett, J. E. (1991). J. Med. Chem. 34, 151–157.  CrossRef PubMed CAS Web of Science Google Scholar
First citationBruker (2001). SMART, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationFarrugia, L. J. (1997). J. Appl. Cryst. 30, 565.  CrossRef IUCr Journals Google Scholar
First citationFeng, X. M., Chen, R. & Yang, W. D. (1992). Chem. J. Chin. Univ. 13, 187–194.  CAS Google Scholar
First citationHeidelberger, C., Chaudhuri, N. K., Danneberg, P., Mooren, D., Greisbach, L., Duschinsky, R., Scnnitzer, R. J., Pleaven, E. & Scheiner, J. (1957). Nature (London), 179, 663–666.  CrossRef PubMed CAS Web of Science Google Scholar
First citationHeindel, N. D. & Reid, J. R. (1980). J. Heterocycl. Chem. 17, 1087–1088.  CrossRef CAS Google Scholar
First citationHirota, T., Sasaki, K., Yamamoto, H. & Nakayama, T. (1991). J. Heterocycl. Chem. 28, 257–261.  CrossRef CAS Google Scholar
First citationHolla, B. S., Akberali, P. M. & Shivananda, M. K. (2001). Il Farmaco, 56, 919–927.  Web of Science CrossRef PubMed CAS Google Scholar
First citationMohan, J. & Anjaneyalu, G. S. R. (1987). Pol. J. Chem. 61, 547–551.  CAS Google Scholar
First citationNovak, M. J., Baum, J. C. & Buhrow, J. A. (2006). Olson. Surf. Sci. 600, L269–L273.  Web of Science CrossRef CAS Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationWalser, A., Flynn, T. & Mason, C. (1991). J. Heterocycl. Chem. 28, 1121–1125.  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