(E)-N-(3,4-Di­methyl­phen­yl)-1-[5-(phenyl­ethyn­yl)thio­phen-2-yl]methanimine

Crundwell, G.; Crundwell, H.I.

doi:10.1107/S2414314619003638

organic compounds

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ISSN: 2414-3146

Volume 4| Part 4| April 2019| x190363

https://doi.org/10.1107/S2414314619003638

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(E)-N-(3,4-Dimethylphenyl)-1-[5-(phenylethynyl)thiophen-2-yl]methanimine

Guy Crundwell ^a ^* and Hugh Ian Crundwell ^a

^aDepartment of Chemistry & Biochemistry, Central Connecticut State University, 1619 Stanley Street, New Britain, CT 06053, USA
^*Correspondence e-mail: crundwellg@ccsu.edu

Edited by S. Bernès, Benemérita Universidad Autónoma de Puebla, México (Received 20 February 2019; accepted 14 March 2019; online 5 April 2019)

The title compound, C₂₁H₁₇NS, was synthesized via the reaction of 5-(2-phenyleth-1-ynyl)thiophene-2-carbaldehyde and 3,4-dimethylaniline using ammonium bifluoride (NH₄HF₂) as an acid catalyst in methanol. The molecule has three aryl rings: a phenyl (A), a thiophene (B), and a dimethylbenzene ring (C). The dihedral angles between the mean planes defined by these individual rings are 14.88 (6)° for A/B and 43.93 (4)° for B/C.

Keywords: crystal structure; imine; thiophene.

CCDC reference: 1903308

Structure description

Imine formation between thiophenecarbaldehydes and anilines are prevalent in the chemical literature. Not only are they of interest as potential drug candidates, as antibacterial and/or antifungal agents (Shanty et al., 2017 ), but they are also interesting ligands (Belkhiria et al., 2018 ). Our interests are in quinoxaline formation. The synthetic method using ammonium bifluoride as an acid catalyst outlined by Lassagne and co-workers (Lassagne et al., 2015 ) has proven to be a clean high-yielding method for the synthesis quinoxalines and in addition for the production of imines. This reaction is proof for the clean high-yield production of imines as well.

In the molecule (Fig. 1), all bond lengths and angles are within expected values. Molecules associated by inversion have intermolecular contacts between the imine nitrogen (N1) and a hydrogen on a neighboring methyl group (C20). The overall packing (Fig. 2) resembles the classic herringbone pattern.

Figure 1
ORTEP view of the title compound, with 50% probability displacement ellipsoids.

Figure 2
A view along [100] showing short packing contacts between imine N atoms and methyl H atoms on neighboring molecules (Macrae et al., 2008

Synthesis and crystallization

To a 50 ml Erlenmeyer flask, 1.00 mmol of 5-(2-phenyleth-1-ynyl)thiophene-2-carbaldehyde (212 mg) was stirred into 10 ml of 2.5 × 10⁻³ mol l⁻¹ solution of NH₄HF₂ in methanol. After the solid aldehyde had dissolved, 1.00 mmol of 3,4-dimethylaniline (121 mg) was added. Within the first 5 min, the amine also dissolved; however, within an hour, the product had begun to precipitate. The reaction was allowed to continue stirring overnight to ensure completion. Once filtered, the yellow solid product was washed with two 2 ml aliquots of ice cold 50:50 methanol–water, and once dried, 287 mg of product was formed (91.0% yield). This procedure is similar, though not identical, to a method used by Lassagne and co-workers to form quinoxalines and pyrido[2,3-b]pyrazines (Lassagne et al., 2015). Crystals for diffraction study were crystallized from methylene chloride (m.p. 410 K). ATR–IR (cm⁻¹): 3059, 2971, 2918, 1882, 1612, 1486, 1440, 1020, 826, 806. ¹H NMR (300 MHz, CDCl₃): δ 8.54 (s, 1H), 7.58 (m, 2H), 7.40 (m, 4H), 7.30 (t, 1H), 7.17 (d, 1H), 7.08 (d, 1H), 7.04 (dd, 1H), 2.31 (d, 6H). ¹³C (75 MHz, CDCl₃): δ 151.17, 148.88, 144.11, 137.42, 134.96, 132.37, 131.58, 131.40, 130.32, 128.83, 128.46, 127.35, 122.56, 118.24, 95.68, 82.86, 19.86, 19.40. F T–IR, ¹H NMR, COSY and ¹³C NMR are given in the supporting information.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1.

Table 1
Experimental details

Crystal data
Chemical formula	C₂₁H₁₇NS
M_r	315.42
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	293
a, b, c (Å)	5.9435 (3), 22.7785 (7), 15.0910 (9)
β (°)	124.087 (8)
V (Å³)	1692.06 (14)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.19
Crystal size (mm)	0.49 × 0.43 × 0.23

Data collection
Diffractometer	Rigaku Xcalibur Sapphire3
Absorption correction	Multi-scan (CrysAlis PRO; Rigaku OD, 2015 )
T_min, T_max	0.754, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	42768, 6330, 4181
R_int	0.035
(sin θ/λ)_max (Å⁻¹)	0.779

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.046, 0.131, 1.03
No. of reflections	6330
No. of parameters	210
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.21, −0.23
Computer programs: CrysAlis PRO (Rigaku OD, 2015), SHELXT (Sheldrick, 2015a ), SHELXL (Sheldrick, 2015b ) and OLEX2 (Dolomanov et al., 2009 ).

Structural data

CCDC reference: 1903308

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314619003638/bh4045sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314619003638/bh4045Isup2.hkl

Supplementary Material (FTIR/NMR). DOI: https://doi.org/10.1107/S2414314619003638/bh4045sup3.pdf

Supporting information file. DOI: https://doi.org/10.1107/S2414314619003638/bh4045Isup4.cml

checkCIF report

Computing details top

Data collection: CrysAlis PRO (Rigaku OD, 2015); cell refinement: CrysAlis PRO (Rigaku OD, 2015); data reduction: CrysAlis PRO (Rigaku OD, 2015); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

(E)-N-(3,4-Dimethylphenyl)-1-[5-(phenylethynyl)thiophen-2-yl]methanimine top

Crystal data top

C₂₁H₁₇NS	D_x = 1.238 Mg m⁻³
M_r = 315.42	Melting point: 410 K
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 5.9435 (3) Å	Cell parameters from 8633 reflections
b = 22.7785 (7) Å	θ = 4.2–31.1°
c = 15.0910 (9) Å	µ = 0.19 mm⁻¹
β = 124.087 (8)°	T = 293 K
V = 1692.06 (14) Å³	Plate, yellow
Z = 4	0.49 × 0.43 × 0.23 mm
F(000) = 664

Data collection top

Xcalibur, Sapphire3 diffractometer	6330 independent reflections
Radiation source: fine-focus sealed X-ray tube, Enhance (Mo) X-ray Source	4181 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.035
Detector resolution: 16.1790 pixels mm^-1	θ_max = 33.6°, θ_min = 4.2°
ω scans	h = −9→9
Absorption correction: multi-scan (CrysAlis PRO; Rigaku OD, 2015)	k = −35→35
T_min = 0.754, T_max = 1.000	l = −23→23
42768 measured reflections

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.046	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.131	H-atom parameters constrained
S = 1.03	w = 1/[σ²(F_o²) + (0.0574P)² + 0.2177P] where P = (F_o² + 2F_c²)/3
6330 reflections	(Δ/σ)_max = 0.001
210 parameters	Δρ_max = 0.21 e Å⁻³
0 restraints	Δρ_min = −0.23 e Å⁻³

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

	x	y	z	U_iso*/U_eq
C1	0.4721 (3)	0.73831 (6)	−0.25547 (12)	0.0574 (3)
H1	0.6539	0.7351	−0.1992	0.069*
C2	0.3977 (4)	0.77446 (7)	−0.34126 (14)	0.0692 (4)
H2	0.5296	0.7957	−0.3424	0.083*
C3	0.1302 (4)	0.77907 (7)	−0.42473 (14)	0.0712 (4)
H3	0.0812	0.8035	−0.4823	0.085*
C4	−0.0653 (3)	0.74777 (7)	−0.42359 (13)	0.0678 (4)
H4	−0.2463	0.7509	−0.4806	0.081*
C5	0.0053 (3)	0.71160 (6)	−0.33820 (11)	0.0538 (3)
H5	−0.1283	0.6906	−0.3378	0.065*
C6	0.2751 (3)	0.70658 (5)	−0.25309 (9)	0.0442 (3)
C7	0.3453 (3)	0.66938 (6)	−0.16471 (10)	0.0491 (3)
C8	0.3928 (3)	0.63856 (6)	−0.09161 (10)	0.0496 (3)
C9	0.4458 (3)	0.60085 (5)	−0.00742 (9)	0.0445 (3)
C10	0.2630 (3)	0.57639 (6)	0.00958 (11)	0.0505 (3)
H10	0.0772	0.5837	−0.0334	0.061*
C11	0.3859 (3)	0.53910 (6)	0.09894 (11)	0.0500 (3)
H11	0.2902	0.5195	0.1219	0.060*
C12	0.6603 (3)	0.53453 (5)	0.14866 (10)	0.0436 (3)
C13	0.8443 (3)	0.49621 (5)	0.23642 (10)	0.0458 (3)
H13	0.7823	0.4768	0.2731	0.055*
C14	1.2578 (2)	0.45061 (5)	0.35353 (10)	0.0427 (2)
C15	1.2450 (3)	0.44648 (6)	0.44287 (10)	0.0458 (3)
H15	1.1172	0.4688	0.4451	0.055*
C16	1.4172 (3)	0.41012 (5)	0.52816 (10)	0.0454 (3)
C17	1.6122 (3)	0.37701 (5)	0.52561 (10)	0.0475 (3)
C18	1.6256 (3)	0.38167 (6)	0.43691 (11)	0.0511 (3)
H18	1.7548	0.3599	0.4348	0.061*
C19	1.4519 (3)	0.41790 (6)	0.35167 (11)	0.0484 (3)
H19	1.4652	0.4203	0.2932	0.058*
C20	1.3950 (3)	0.40764 (8)	0.62267 (12)	0.0634 (4)
H20A	1.5619	0.4210	0.6855	0.095*
H20B	1.3602	0.3680	0.6332	0.095*
H20C	1.2486	0.4324	0.6096	0.095*
C21	1.8056 (3)	0.33707 (8)	0.61696 (13)	0.0674 (4)
H21A	1.9227	0.3601	0.6799	0.101*
H21B	1.9131	0.3156	0.5986	0.101*
H21C	1.7042	0.3101	0.6305	0.101*
N1	1.0880 (2)	0.48807 (5)	0.26526 (8)	0.0469 (2)
S1	0.77294 (7)	0.578178 (15)	0.08798 (3)	0.04885 (10)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0533 (8)	0.0607 (8)	0.0519 (7)	−0.0092 (6)	0.0255 (6)	−0.0024 (6)
C2	0.0825 (11)	0.0612 (9)	0.0725 (10)	−0.0169 (8)	0.0487 (9)	0.0023 (8)
C3	0.0916 (12)	0.0555 (8)	0.0620 (9)	0.0016 (8)	0.0402 (9)	0.0168 (7)
C4	0.0609 (9)	0.0654 (9)	0.0572 (9)	0.0076 (7)	0.0208 (7)	0.0174 (7)
C5	0.0488 (7)	0.0535 (7)	0.0527 (7)	−0.0009 (6)	0.0246 (6)	0.0068 (6)
C6	0.0510 (7)	0.0400 (6)	0.0396 (6)	−0.0003 (5)	0.0242 (5)	−0.0015 (4)
C7	0.0533 (7)	0.0476 (6)	0.0422 (6)	−0.0008 (5)	0.0242 (6)	−0.0013 (5)
C8	0.0549 (7)	0.0470 (6)	0.0416 (6)	0.0017 (5)	0.0238 (6)	−0.0011 (5)
C9	0.0516 (7)	0.0426 (6)	0.0374 (5)	0.0029 (5)	0.0238 (5)	−0.0018 (5)
C10	0.0455 (7)	0.0518 (7)	0.0509 (7)	0.0035 (5)	0.0250 (6)	0.0023 (6)
C11	0.0497 (7)	0.0507 (7)	0.0540 (7)	−0.0002 (5)	0.0317 (6)	0.0042 (6)
C12	0.0502 (7)	0.0426 (6)	0.0420 (6)	0.0006 (5)	0.0284 (5)	0.0004 (5)
C13	0.0514 (7)	0.0450 (6)	0.0437 (6)	−0.0014 (5)	0.0283 (6)	0.0039 (5)
C14	0.0433 (6)	0.0425 (6)	0.0413 (6)	−0.0043 (5)	0.0229 (5)	0.0037 (5)
C15	0.0488 (7)	0.0460 (6)	0.0442 (6)	−0.0003 (5)	0.0270 (6)	0.0006 (5)
C16	0.0487 (7)	0.0458 (6)	0.0393 (6)	−0.0086 (5)	0.0231 (5)	−0.0007 (5)
C17	0.0433 (6)	0.0455 (6)	0.0455 (6)	−0.0052 (5)	0.0200 (5)	0.0040 (5)
C18	0.0452 (7)	0.0537 (7)	0.0551 (7)	0.0020 (5)	0.0284 (6)	0.0027 (6)
C19	0.0485 (7)	0.0551 (7)	0.0478 (7)	−0.0014 (5)	0.0308 (6)	0.0036 (5)
C20	0.0668 (9)	0.0800 (10)	0.0464 (7)	−0.0015 (8)	0.0336 (7)	0.0066 (7)
C21	0.0597 (9)	0.0708 (10)	0.0608 (9)	0.0082 (7)	0.0271 (8)	0.0204 (8)
N1	0.0496 (6)	0.0479 (5)	0.0422 (5)	−0.0003 (4)	0.0251 (5)	0.0063 (4)
S1	0.04729 (18)	0.05599 (19)	0.04635 (18)	0.00247 (13)	0.02812 (15)	0.00812 (13)

Geometric parameters (Å, º) top

C1—H1	0.9300	C12—S1	1.7210 (12)
C1—C2	1.381 (2)	C13—H13	0.9300
C1—C6	1.3933 (19)	C13—N1	1.2706 (16)
C2—H2	0.9300	C14—C15	1.3956 (17)
C2—C3	1.372 (3)	C14—C19	1.3866 (18)
C3—H3	0.9300	C14—N1	1.4192 (15)
C3—C4	1.372 (2)	C15—H15	0.9300
C4—H4	0.9300	C15—C16	1.3835 (17)
C4—C5	1.3818 (19)	C16—C17	1.4013 (19)
C5—H5	0.9300	C16—C20	1.5054 (18)
C5—C6	1.3880 (18)	C17—C18	1.3889 (19)
C6—C7	1.4308 (17)	C17—C21	1.5076 (19)
C7—C8	1.2002 (18)	C18—H18	0.9300
C8—C9	1.4151 (17)	C18—C19	1.3833 (18)
C9—C10	1.3673 (19)	C19—H19	0.9300
C9—S1	1.7270 (13)	C20—H20A	0.9600
C10—H10	0.9300	C20—H20B	0.9600
C10—C11	1.4033 (18)	C20—H20C	0.9600
C11—H11	0.9300	C21—H21A	0.9600
C11—C12	1.3647 (18)	C21—H21B	0.9600
C12—C13	1.4452 (17)	C21—H21C	0.9600

C2—C1—H1	120.0	N1—C13—H13	118.9
C2—C1—C6	120.08 (14)	C15—C14—N1	123.50 (11)
C6—C1—H1	120.0	C19—C14—C15	118.68 (11)
C1—C2—H2	119.9	C19—C14—N1	117.79 (11)
C3—C2—C1	120.24 (15)	C14—C15—H15	119.1
C3—C2—H2	119.9	C16—C15—C14	121.77 (12)
C2—C3—H3	119.9	C16—C15—H15	119.1
C4—C3—C2	120.20 (14)	C15—C16—C17	119.26 (12)
C4—C3—H3	119.9	C15—C16—C20	119.46 (13)
C3—C4—H4	119.8	C17—C16—C20	121.26 (12)
C3—C4—C5	120.33 (15)	C16—C17—C21	121.21 (12)
C5—C4—H4	119.8	C18—C17—C16	118.71 (12)
C4—C5—H5	119.9	C18—C17—C21	120.08 (13)
C4—C5—C6	120.10 (13)	C17—C18—H18	119.1
C6—C5—H5	119.9	C19—C18—C17	121.72 (12)
C1—C6—C7	121.40 (12)	C19—C18—H18	119.1
C5—C6—C1	119.04 (12)	C14—C19—H19	120.1
C5—C6—C7	119.56 (12)	C18—C19—C14	119.84 (12)
C8—C7—C6	177.09 (15)	C18—C19—H19	120.1
C7—C8—C9	178.38 (14)	C16—C20—H20A	109.5
C8—C9—S1	120.67 (10)	C16—C20—H20B	109.5
C10—C9—C8	127.98 (12)	C16—C20—H20C	109.5
C10—C9—S1	111.32 (10)	H20A—C20—H20B	109.5
C9—C10—H10	123.6	H20A—C20—H20C	109.5
C9—C10—C11	112.74 (12)	H20B—C20—H20C	109.5
C11—C10—H10	123.6	C17—C21—H21A	109.5
C10—C11—H11	123.4	C17—C21—H21B	109.5
C12—C11—C10	113.12 (12)	C17—C21—H21C	109.5
C12—C11—H11	123.4	H21A—C21—H21B	109.5
C11—C12—C13	127.39 (11)	H21A—C21—H21C	109.5
C11—C12—S1	111.39 (9)	H21B—C21—H21C	109.5
C13—C12—S1	121.09 (10)	C13—N1—C14	118.94 (10)
C12—C13—H13	118.9	C12—S1—C9	91.40 (6)
N1—C13—C12	122.27 (11)

Acknowledgements

Funding for this research was provided by a CSU-AAUP Research Grant.

References

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