research communications
d]thiazole
of 2-(2,5-dimethoxyphenyl)benzo[aChemistry Department, Faculty of Science, Cairo University, Giza, Egypt, bChemistry Department, Faculty of Science, Helwan University, Cairo, Egypt, and cInstitut für Anorganische und Analytische Chemie, Technische Universität Braunschweig, Hagenring 30, D-38106 Braunschweig, Germany
*Correspondence e-mail: p.jones@tu-bs.de
The title compound, C15H13NO2S, was synthesized efficiently in the solid state by exploiting pepsin catalysis. The ring systems are nearly coplanar [interplanar angle of 5.38 (2)°] with an associated intramolecular S⋯O=C short contact of 2.7082 (4) Å. The packing involves C—H⋯O, C—H⋯π and π–π contacts.
Keywords: benzothiazole; pepsin catalysis; crystal structure.
CCDC reference: 2161465
1. Chemical context
Although countless synthetic methods are widely available, new and more efficient procedures or approaches are always needed. Enzymes, as `green' catalysts for modern organic synthesis, have attracted increased attention because they may provide alternative and sustainable processes, thus helping to minimize the release of hazardous substances into the environment (Witayakran & Ragauskas, 2009). Pepsin, a kind of hydrolase, belongs to the family of aspartic acid and is involved in chemical digestion of protein (Cooper et al., 1990; Lin et al., 1989). Pepsin-catalysed aldol (and other) reactions have been developed (Li et al., 2010; He et al., 2016; Zongbo et al., 2017).
2-Aryl-benzothiazoles are a class of nitrogen-containing et al. 2017a,b, 2020a,b,c, 2021; Elgemeie et al., 2000a,b, 2020). The conventional synthesis of 2-aryl-benzothiazoles, which involves heating a mixture containing 2-aminothiophenol (1), is disadvantageous because 1 is extremely unstable in air and highly toxic. In a continuation of our recent research in developing `green' and simple syntheses of novel (Metwally et al., 2020, 2021a,b), we have now synthesized 2-(2,5-dimethoxyphenyl)benzo[d]thiazole (3) using pepsin as the `green' catalytic reaction. Thus, a mixture of 1 and 2,5-dimethoxybenzaldehyde 2 was ground in a mortar with 0.05 g pepsin for 10 minutes, providing the desired product 3 in 97% yield. The nature of compound 3 was confirmed by spectroscopic analysis and by the single-crystal X-ray structure reported here.
that can be found in a variety of natural and synthetic compounds. In view of their biological and pharmacological characteristics, we are interested in developing synthetic strategies for heterocyclic ring systems containing a benzothiazole moiety; these have shown significant biological activity as novel antiviral and antimicrobial agents. (Azzam2. Structural commentary
The structure of 3 is shown in Fig. 1. Molecular dimensions may be regarded as normal; a brief selection is presented in Table 1. Both ring systems are effectively planar (r.m.s. values of 0.01 Å for the benzothiazole and 0.004 Å for the phenyl ring, respectively), with an interplanar angle of 5.38 (2)°. The approximate coplanarity leads to the short intramolecular contacts S1⋯O1 = 2.7082 (4) and H16⋯N3 = 2.48 Å; the C16—H16⋯N3 angle is 101°.
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3. Supramolecular features
There are no markedly short intermolecular contacts. One borderline `weak' C—H⋯O hydrogen bond can be identified (Table 2), which links molecules via the c-glide operator x, −y + , z − . This is reinforced by a C—H⋯π contact from H14 to the centroid of the phenyl ring (H14⋯Cg = 2.67 Å, C14—H14⋯Cg = 138°; Cg is the centroid of the C11–C16 ring). Additionally, the molecules are linked in pairs, related by c-axis translation, in which the benzothiazole ring system of one molecule lies opposite the phenyl ring of the other; the intercentroid distances are 3.5651 (3) Å for benzo⋯phenyl, and 3.6022 (3) Å for thiazole⋯phenyl (phenyl operator x, y, −1 + z). The net effect is to form a somewhat flattened herringbone pattern parallel to the c axis (Fig. 2; the π–π interactions are not shown explicitly). The contact C18—H18C⋯N3 (Table 2), involving a methyl group, connects the chains in the third dimension via the operator −x + 1, −y + 1, −z.
4. Database survey
A search of the Cambridge Database (Version 2021.3.0; Groom et al., 2016) gave four hits for purely organic, neutral species in which one benzo[d]thiazole is bonded at its 2-position to an aromatic C6 ring with oxygen substituents at the ortho (2-) and meta (5-) positions. These were CEFWOB [Yousuf et al., 2012; 2-hydroxy, 5-methoxy; no S⋯O contact because of an intramolecular O—H⋯N hydrogen bond; interplanar angle 1.23 (9)°]; NOYSOM [Wang et al., 2019; 2,5-dimethoxy with an additional 4-(2-pyridyl) substituent; two independent molecules; S⋯O = 2.650, 2.715 Å; interplanar angles of 6.0, 5.5°]; UFAHUF [Chen, 2007; 2,4,5-trimethoxy; S⋯O = 2.671 Å, interplanar angle of 4.5 (2)°] and WACPUO (Sakai et al., 2016; 2-hydroxy, 5-methoxy with an additional 3-imidazole substituent; S⋯O = 2.695 Å, interplanar angle of 1.6°). Where not given in the original publications, these values were calculated using the CCDC program Mercury (Macrae et al., 2020).
5. Synthesis and crystallization
A mixture of o-aminothiophenol 1 (0.01 mol), 2,5-dimethoxybenzaldehyde 2 (0.01 mol) and pepsin (0.05 g) was ground together at room temperature for 10 min. The viscous mixture was poured onto ice–water; the solid that formed was filtered off and recrystallized from ethanol to give pale-yellow crystals of 3 in 97% yield, m.p. 414 K; IR (KBr, cm−1): νmax 1581 (C=N); 1H NMR (DMSO-d6): δ = 3.82 (s, 3H, OCH3), 4.0 (s, 3H, OCH3), 7.13–7.15 (m, 1H, Ar), 7.22 (d, 1H, J = 8.8 Hz, Ar), 7.41 (t, 1H, J = 7.6 Hz, Ar), 7.51 (t, 1H, J = 7.6 Hz, Ar), 7.96 (s, 1H, Ar), 8.07 (dd, 2H, J = 8.0 Hz, Ar), 13C NMR (DMSO-d6): δ = 56.0, 57.0, 112.5, 114.7, 119.1, 122.1, 122.2, 122.9, 125.4, 126.7, 136.0, 151.9, 153.8, 154.4, 162.3; m/z = 271 (M+, 100%), 238 (61.4%), 185 (27.6%), 136 (79.0%); Analysis: calculated for C15H13NO2S (271.33) C 66.40, H 4.83, N 5.16, S 11.82%; found C 66.58, H 4.65, N 5.39, S 11.68%.
6. Refinement
Crystal data, data collection and structure . Methyl groups were refined as idealized rigid groups allowed to rotate but not tip (AFIX 137), with C—H = 0.98 Å, H—C—H = 109.5°. Other hydrogen atoms were included using a riding model starting from calculated positions (C—Haromatic = 0.95 Å). The U(H) values were fixed at 1.5 or 1.2 × Ueq of the parent carbon atoms for methyl and aromatic hydrogens, respectively.
details are summarized in Table 3Supporting information
CCDC reference: 2161465
https://doi.org/10.1107/S2056989022003279/vm2262sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989022003279/vm2262Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989022003279/vm2262Isup3.cml
Data collection: CrysAlis PRO (Rigaku OD, 2021); cell
CrysAlis PRO (Rigaku OD, 2021); data reduction: CrysAlis PRO (Rigaku OD, 2021); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015b); molecular graphics: XP (Siemens, 1994); software used to prepare material for publication: SHELXL2018/3 (Sheldrick, 2015b).C15H13NO2S | F(000) = 568 |
Mr = 271.32 | Dx = 1.435 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 14.6666 (2) Å | Cell parameters from 88513 reflections |
b = 13.8922 (2) Å | θ = 2.8–38.4° |
c = 6.26063 (10) Å | µ = 0.25 mm−1 |
β = 100.1273 (14)° | T = 100 K |
V = 1255.74 (3) Å3 | Block, colourless |
Z = 4 | 0.22 × 0.22 × 0.15 mm |
XtaLAB Synergy, HyPix diffractometer | 6759 independent reflections |
Radiation source: micro-focus sealed X-ray tube | 6156 reflections with I > 2σ(I) |
Detector resolution: 10.0000 pixels mm-1 | Rint = 0.023 |
ω scans | θmax = 38.3°, θmin = 2.0° |
Absorption correction: multi-scan (CrysAlisPro; Rigaku OD, 2021) | h = −24→25 |
Tmin = 0.927, Tmax = 1.000 | k = −23→23 |
123768 measured reflections | l = −10→10 |
Refinement on F2 | Primary atom site location: dual |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.027 | H-atom parameters constrained |
wR(F2) = 0.084 | w = 1/[σ2(Fo2) + (0.0489P)2 + 0.2455P] where P = (Fo2 + 2Fc2)/3 |
S = 1.03 | (Δ/σ)max = 0.001 |
6759 reflections | Δρmax = 0.62 e Å−3 |
174 parameters | Δρmin = −0.19 e Å−3 |
0 restraints |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane) - 0.2606 (0.0025) x + 11.3686 (0.0009) y - 3.5208 (0.0006) z = 4.3561 (0.0009) * -0.0113 (0.0003) S1 * 0.0122 (0.0004) C2 * 0.0073 (0.0004) N3 * -0.0022 (0.0005) C3A * -0.0178 (0.0004) C4 * 0.0029 (0.0005) C5 * 0.0151 (0.0005) C6 * -0.0033 (0.0005) C7 * -0.0029 (0.0005) C7A Rms deviation of fitted atoms = 0.0101 - 1.6150 (0.0031) x + 11.4261 (0.0017) y - 3.3180 (0.0011) z = 4.1087 (0.0012) Angle to previous plane (with approximate esd) = 5.381 ( 0.023 ) * -0.0035 (0.0003) C11 * 0.0058 (0.0004) C12 * -0.0025 (0.0004) C13 * -0.0031 (0.0004) C14 * 0.0054 (0.0004) C15 * -0.0020 (0.0004) C16 -0.0003 (0.0008) O1 0.0801 (0.0011) C17 0.0285 (0.0008) O2 0.1636 (0.0010) C18 Rms deviation of fitted atoms = 0.0040 |
x | y | z | Uiso*/Ueq | ||
S1 | 0.13465 (2) | 0.49165 (2) | 0.34350 (2) | 0.01451 (4) | |
C2 | 0.24674 (4) | 0.47726 (4) | 0.28209 (8) | 0.01188 (8) | |
N3 | 0.31247 (3) | 0.52002 (3) | 0.41668 (7) | 0.01347 (7) | |
C3A | 0.27752 (4) | 0.56826 (4) | 0.57771 (8) | 0.01360 (8) | |
C4 | 0.33134 (4) | 0.62033 (4) | 0.74630 (9) | 0.01695 (9) | |
H4 | 0.396755 | 0.623486 | 0.758537 | 0.020* | |
C5 | 0.28692 (5) | 0.66707 (4) | 0.89466 (9) | 0.01963 (10) | |
H5 | 0.322334 | 0.703577 | 1.008219 | 0.024* | |
C6 | 0.19042 (5) | 0.66133 (5) | 0.87976 (10) | 0.02095 (11) | |
H6 | 0.161650 | 0.694472 | 0.982862 | 0.025* | |
C7 | 0.13610 (5) | 0.60805 (4) | 0.71696 (10) | 0.01924 (10) | |
H7 | 0.071002 | 0.603042 | 0.709129 | 0.023* | |
C7A | 0.18087 (4) | 0.56196 (4) | 0.56475 (9) | 0.01468 (8) | |
C11 | 0.26660 (3) | 0.42388 (3) | 0.09270 (8) | 0.01131 (7) | |
C12 | 0.19879 (3) | 0.37320 (4) | −0.05164 (8) | 0.01179 (8) | |
C13 | 0.22303 (4) | 0.32478 (4) | −0.22766 (8) | 0.01295 (8) | |
H13 | 0.177114 | 0.290066 | −0.323243 | 0.016* | |
C14 | 0.31402 (4) | 0.32648 (4) | −0.26592 (8) | 0.01283 (8) | |
H14 | 0.329903 | 0.293120 | −0.386674 | 0.015* | |
C15 | 0.38132 (3) | 0.37743 (4) | −0.12577 (8) | 0.01215 (8) | |
C16 | 0.35765 (4) | 0.42522 (4) | 0.05254 (8) | 0.01240 (8) | |
H16 | 0.404004 | 0.459248 | 0.148423 | 0.015* | |
O1 | 0.11061 (3) | 0.37347 (3) | −0.00594 (7) | 0.01587 (7) | |
C17 | 0.04056 (4) | 0.32676 (5) | −0.15693 (10) | 0.01998 (10) | |
H17A | 0.036645 | 0.356648 | −0.300050 | 0.030* | |
H17B | −0.019153 | 0.333071 | −0.108453 | 0.030* | |
H17C | 0.056005 | 0.258430 | −0.166186 | 0.030* | |
O2 | 0.47191 (3) | 0.38509 (3) | −0.15047 (7) | 0.01691 (8) | |
C18 | 0.49545 (4) | 0.34434 (5) | −0.34295 (10) | 0.01952 (10) | |
H18A | 0.454902 | 0.371139 | −0.470203 | 0.029* | |
H18B | 0.487554 | 0.274329 | −0.340465 | 0.029* | |
H18C | 0.560067 | 0.359596 | −0.350301 | 0.029* |
U11 | U22 | U33 | U12 | U13 | U23 | |
S1 | 0.01415 (6) | 0.01602 (6) | 0.01373 (6) | 0.00148 (4) | 0.00352 (4) | −0.00175 (4) |
C2 | 0.01436 (18) | 0.01083 (17) | 0.01076 (17) | 0.00014 (14) | 0.00307 (14) | 0.00011 (13) |
N3 | 0.01641 (18) | 0.01302 (17) | 0.01139 (16) | −0.00157 (13) | 0.00354 (13) | −0.00175 (13) |
C3A | 0.0193 (2) | 0.01086 (18) | 0.01120 (17) | −0.00042 (15) | 0.00426 (15) | −0.00038 (14) |
C4 | 0.0236 (2) | 0.0142 (2) | 0.01336 (19) | −0.00312 (17) | 0.00403 (17) | −0.00254 (15) |
C5 | 0.0314 (3) | 0.0140 (2) | 0.0142 (2) | −0.00201 (19) | 0.00606 (19) | −0.00317 (16) |
C6 | 0.0321 (3) | 0.0161 (2) | 0.0167 (2) | 0.0025 (2) | 0.0097 (2) | −0.00306 (17) |
C7 | 0.0239 (2) | 0.0180 (2) | 0.0176 (2) | 0.00356 (19) | 0.00846 (19) | −0.00219 (18) |
C7A | 0.0190 (2) | 0.01267 (19) | 0.01312 (18) | 0.00175 (15) | 0.00489 (15) | −0.00059 (15) |
C11 | 0.01340 (17) | 0.01037 (17) | 0.01029 (16) | 0.00010 (13) | 0.00241 (13) | −0.00034 (13) |
C12 | 0.01206 (17) | 0.01134 (18) | 0.01187 (17) | 0.00064 (13) | 0.00182 (14) | −0.00025 (13) |
C13 | 0.01318 (18) | 0.01267 (18) | 0.01268 (18) | 0.00015 (14) | 0.00138 (14) | −0.00222 (14) |
C14 | 0.01418 (18) | 0.01223 (18) | 0.01217 (18) | 0.00012 (14) | 0.00257 (14) | −0.00183 (14) |
C15 | 0.01276 (18) | 0.01177 (18) | 0.01232 (17) | −0.00073 (14) | 0.00333 (14) | −0.00073 (14) |
C16 | 0.01365 (18) | 0.01212 (18) | 0.01161 (17) | −0.00128 (14) | 0.00273 (14) | −0.00118 (14) |
O1 | 0.01170 (15) | 0.01927 (18) | 0.01672 (16) | −0.00048 (12) | 0.00270 (12) | −0.00411 (13) |
C17 | 0.01240 (19) | 0.0272 (3) | 0.0192 (2) | −0.00078 (18) | −0.00011 (17) | −0.0035 (2) |
O2 | 0.01379 (16) | 0.02132 (19) | 0.01681 (17) | −0.00358 (13) | 0.00599 (13) | −0.00600 (14) |
C18 | 0.0175 (2) | 0.0238 (3) | 0.0190 (2) | −0.00194 (19) | 0.00813 (18) | −0.00580 (19) |
S1—C7A | 1.7327 (6) | C15—O2 | 1.3686 (6) |
S1—C2 | 1.7642 (5) | C15—C16 | 1.3941 (7) |
C2—N3 | 1.3064 (7) | O1—C17 | 1.4243 (7) |
C2—C11 | 1.4704 (7) | O2—C18 | 1.4276 (7) |
N3—C3A | 1.3820 (7) | C4—H4 | 0.9500 |
C3A—C4 | 1.4027 (8) | C5—H5 | 0.9500 |
C3A—C7A | 1.4082 (8) | C6—H6 | 0.9500 |
C4—C5 | 1.3862 (8) | C7—H7 | 0.9500 |
C5—C6 | 1.4043 (10) | C13—H13 | 0.9500 |
C6—C7 | 1.3912 (9) | C14—H14 | 0.9500 |
C7—C7A | 1.4032 (8) | C16—H16 | 0.9500 |
C11—C16 | 1.4017 (7) | C17—H17A | 0.9800 |
C11—C12 | 1.4091 (7) | C17—H17B | 0.9800 |
C12—O1 | 1.3728 (6) | C17—H17C | 0.9800 |
C12—C13 | 1.3896 (7) | C18—H18A | 0.9800 |
C13—C14 | 1.3969 (7) | C18—H18B | 0.9800 |
C14—C15 | 1.3930 (7) | C18—H18C | 0.9800 |
C7A—S1—C2 | 89.40 (3) | C15—O2—C18 | 116.63 (4) |
N3—C2—C11 | 121.40 (5) | C5—C4—H4 | 120.7 |
N3—C2—S1 | 114.72 (4) | C3A—C4—H4 | 120.7 |
C11—C2—S1 | 123.86 (4) | C4—C5—H5 | 119.5 |
C2—N3—C3A | 111.39 (5) | C6—C5—H5 | 119.5 |
N3—C3A—C4 | 124.55 (5) | C7—C6—H6 | 119.4 |
N3—C3A—C7A | 115.25 (5) | C5—C6—H6 | 119.4 |
C4—C3A—C7A | 120.20 (5) | C6—C7—H7 | 121.2 |
C5—C4—C3A | 118.50 (6) | C7A—C7—H7 | 121.2 |
C4—C5—C6 | 121.05 (6) | C12—C13—H13 | 119.6 |
C7—C6—C5 | 121.30 (5) | C14—C13—H13 | 119.6 |
C6—C7—C7A | 117.66 (6) | C15—C14—H14 | 120.2 |
C7—C7A—C3A | 121.26 (5) | C13—C14—H14 | 120.2 |
C7—C7A—S1 | 129.51 (5) | C15—C16—H16 | 119.5 |
C3A—C7A—S1 | 109.23 (4) | C11—C16—H16 | 119.5 |
C16—C11—C12 | 118.61 (4) | O1—C17—H17A | 109.5 |
C16—C11—C2 | 117.91 (4) | O1—C17—H17B | 109.5 |
C12—C11—C2 | 123.47 (4) | H17A—C17—H17B | 109.5 |
O1—C12—C13 | 123.26 (5) | O1—C17—H17C | 109.5 |
O1—C12—C11 | 116.71 (4) | H17A—C17—H17C | 109.5 |
C13—C12—C11 | 120.02 (5) | H17B—C17—H17C | 109.5 |
C12—C13—C14 | 120.88 (5) | O2—C18—H18A | 109.5 |
C15—C14—C13 | 119.54 (5) | O2—C18—H18B | 109.5 |
O2—C15—C14 | 124.24 (5) | H18A—C18—H18B | 109.5 |
O2—C15—C16 | 115.90 (4) | O2—C18—H18C | 109.5 |
C14—C15—C16 | 119.85 (5) | H18A—C18—H18C | 109.5 |
C15—C16—C11 | 121.10 (5) | H18B—C18—H18C | 109.5 |
C12—O1—C17 | 117.16 (4) | ||
C7A—S1—C2—N3 | 0.85 (4) | S1—C2—C11—C16 | 174.46 (4) |
C7A—S1—C2—C11 | −177.67 (4) | N3—C2—C11—C12 | 177.18 (5) |
C11—C2—N3—C3A | 177.97 (4) | S1—C2—C11—C12 | −4.38 (7) |
S1—C2—N3—C3A | −0.60 (6) | C16—C11—C12—O1 | 179.80 (5) |
C2—N3—C3A—C4 | 179.57 (5) | C2—C11—C12—O1 | −1.36 (7) |
C2—N3—C3A—C7A | −0.08 (7) | C16—C11—C12—C13 | 0.89 (7) |
N3—C3A—C4—C5 | 178.64 (5) | C2—C11—C12—C13 | 179.73 (5) |
C7A—C3A—C4—C5 | −1.73 (8) | O1—C12—C13—C14 | −179.65 (5) |
C3A—C4—C5—C6 | 1.12 (9) | C11—C12—C13—C14 | −0.81 (8) |
C4—C5—C6—C7 | 0.50 (10) | C12—C13—C14—C15 | −0.03 (8) |
C5—C6—C7—C7A | −1.46 (9) | C13—C14—C15—O2 | −178.84 (5) |
C6—C7—C7A—C3A | 0.83 (9) | C13—C14—C15—C16 | 0.78 (8) |
C6—C7—C7A—S1 | −179.51 (5) | O2—C15—C16—C11 | 178.96 (5) |
N3—C3A—C7A—C7 | −179.57 (5) | C14—C15—C16—C11 | −0.69 (8) |
C4—C3A—C7A—C7 | 0.76 (8) | C12—C11—C16—C15 | −0.14 (7) |
N3—C3A—C7A—S1 | 0.70 (6) | C2—C11—C16—C15 | −179.05 (5) |
C4—C3A—C7A—S1 | −178.96 (4) | C13—C12—O1—C17 | −4.35 (8) |
C2—S1—C7A—C7 | 179.48 (6) | C11—C12—O1—C17 | 176.78 (5) |
C2—S1—C7A—C3A | −0.82 (4) | C14—C15—O2—C18 | 5.35 (8) |
N3—C2—C11—C16 | −3.97 (7) | C16—C15—O2—C18 | −174.28 (5) |
D—H···A | D—H | H···A | D···A | D—H···A |
C13—H13···O1i | 0.95 | 2.65 | 3.5113 (7) | 151 |
C18—H18C···N3ii | 0.98 | 2.60 | 3.4867 (8) | 151 |
Symmetry codes: (i) x, −y+1/2, z−1/2; (ii) −x+1, −y+1, −z. |
Acknowledgements
The authors acknowledge support by the Open Access Publication Funds of the Technical University of Braunschweig.
References
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