5-Nitro-N-phenyl-2-thio­fur­amide

The title compound, C₁₁H₈N₂O₃S, crystallizes with two crystallographically independent mol­ecules, which are conformationally almost identical, per asymmetric unit. The dihedral angles between the phenyl and 2-thio­fur­amide planes are 46.3 (1) and 47.0 (1)° for the first and second mol­ecule, respectively. Strong intramolecular N—H...O hydrogen bonds [N...O 2.664 (2) and 2.661 (2) Å] dictate an anti conformation of the C=S groups in relation to the furan-O atoms.

S1. Comment

5-Nitrofurans substituted in the 2-position became very important after their biological activity was discovered about 30 years ago by Dodd et al. (1970). Numerous papers have been published on the chemistry of biological and pharmacological studies of 5-nitrofuran derivatives, mostly concerning antibacterial activities. Moreover, it is established that some thioamides exhibit pharmacological activity (Landquist, 1984). In the course of our studies of the syntheses and reactions of furan and 5-nitrofuran thioamides (Hahn et al., 1970; Mance & Jakopčić, 1994), we have now prepared and structurally characterized the title compound, (I); its anti-tumor activity is currently under preliminary investigation. \sch

The title compound crystallizes with two crystallographically independent molecules per asymmetric unit (Fig.1.) The difference in orientation of the phenyl rings is less than 1° indicating that molecules are esssentially identical, but they are not mutually connected by any global symmetry element. The dihedral angles between two planes defined by thiofuramide moiety and phenyl ring atoms amount to 46.3 (1) and 47.0 (1)° for the first and second molecule, respectively. The molecules are not planar, exhibiting twisting around the single Nsp²—Csp² bond (N11—C61 and N12—C62, respectively). The measure of twisting is described by torsion angles of 137.8 (2) and -138.1 (2)° for C71—C61—N11—C11 and C72—C62—N12—C12, respectively.

A survey of the Cambridge Crystallographic Database (Version 5.17; Allen & Kennard, 1993) revealed 60 structures containing the 5-nitro-2-furyl moiety and only four with the 5-nitro-2,5-dihydrofuryl fragment. Moreover, the structure of only one thiofuramide i.e. N-(2-hydroxyethyl)-2-thiofuramide is known up to now (Galešić et al., 1987).

The bond distances in both molecules are the same within the 3σ criterion. The Csp²═Csp² bond distance values within the furan ring are the same and in agreement with the literature data (Allen et al., 1987), while Csp²—Csp² single bond [C31—C41 1.398 (4) and C32—C42 1.403 (3) Å] is slightly shorter (average value 1.423 Å) (Allen et al., 1987). The Csp²—O bond values [O11—C21 1.374 (3), O11—C51 1.351 (3), O12—C22 1.377 (2) and O12—C52 1.347 (3) Å] correspond with the average O-Csp² value of 1.368 Å (Allen et al., 1987). However, the O11—C51 and O12—C52 distances are shortened by the effect of the NO₂ groups directly attached to C51 and C52. The pattern of one shorter and one longer O-Csp² bond distance of 1.350 Å and 1.375 Å, respectively, is observed in all database structures containing the 5-nitro-2-furyl fragment.

The C═S bonds [C11—S11 1.655 (2) and C12—S12 1.655 (2) Å] are slightly shorter than those found in the structural fragment (X)₂—C=S (X = C,N,O,S), 1.671 Å (Allen et al., 1987) and in N-(2-hydroxyethyl)-2-thiofuramide (Galešić et al., 1987), 1.673 (3) Å. Such shortening, associated with the significant π character of N11—C11 and N12—C12 [1.344 (3) and 1.348 (3) Å, respectively] is in agreement with delocalization of π electrons within the 5-nitro-2-thiofuramide moieties. In the structure of N-(2-hydroxyethyl)-2-thiofuramide (Galešić et al., 1987) the analogous bond length is even shorter at 1.317 (4) Å.

The angle sum around thiofuramide N atoms N11 and N12 are 359.9 (2) and 359.6 (2)°, confirming sp² hybridization. The N11—C61 and N12—C62 bond lengths of 1.419 (3) and 1.422 (3) Å are shorter even than the partially delocalized single N-Csp³ bond distance value of 1.460 (3) Å found in N-(2-hydroxyethyl)-2-thiofuramide (Galešić et al., 1987).

The anti conformation (spatial orientation of C=S group with respect to the furan oxygen) of the molecules is adopted as a result of intramolecular hydrogen bonding of the type N—H···O (Table 2; Taylor et al., 1984). The packing also involves two weak intermolecular C—H···O hydrogen bonds involving NO₂ oxygen atoms and phenyl C—H proton donors (Table 2).

S2. Experimental

We employed an alternative preparation of N-phenyl-5-nitro-2-thiofuramide by thionation of furancarboxamide with Lawesson's reagent (Cava & Levinson, 1985) instead of phosphorous pentasulfide (Mance & Jakopčić, 1994; Fãrcasãn & Paiu, 1966). To a solution of N-phenyl-5-nitro-2-furamide (2.3 g, 10 mmol) in dry ethyleneglycoldimethylether (15 ml) Lawesson's reagent (2.2 g, 5.4 mmol) was added. The reaction mixture was heated at 333 K for 30 minutes and solvent evaporated. The product was chromatographed on a silica gel column with petroleum ether/chloroform, 1:1. The purified product (2.4 g, 96%) obtained on evaporation of the solvents was recrystallized from ethanol, yielding red crystals (m.p. = 414–415 K) suitable for X-ray single-crystal diffractometry.

S3. Refinement

The structure was solved by direct methods and refined anisotropically on F². Hydrogen atoms of furan and phenyl rings were generated at idealized geometrical positions with C—H distance 0.93 Å and U_iso(H) = 1.2 U_iso of the carrier C atom, and refined using a riding model. The hydrogen atoms H11 and H12 were identified in difference Fourier maps, but in the final stage of refinement they were generated and refined by applying riding model (N—H 0.93 Å).

Computing details

Data collection: STADI4 (Stoe & Cie, 1995a); cell refinement: STADI4; data reduction: X-RED (Stoe & Cie, 1995b); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON98 (Spek, 1998); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. A perspective view of the two independent molecules of (I) showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. The hydrogen atoms are drawn as small circles of arbitrary radius. The intramolecular hydrogen bonds are indicated by dashed lines.

N-phenyl-5-nitro-2-thiofuramide

Crystal data

C11H8N2O3S	F(000) = 512
Mr = 248.25	Dx = 1.486 Mg m^−3
Triclinic, P1	Melting point = 414–415 K
a = 7.499 (1) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.114 (2) Å	Cell parameters from 28 reflections
c = 16.717 (2) Å	θ = 10.1–14.9°
α = 86.06 (2)°	µ = 0.29 mm^−1
β = 88.61 (1)°	T = 293 K
γ = 76.73 (2)°	Prism, red
V = 1109.4 (3) Å^3	0.76 × 0.53 × 0.24 mm
Z = 4

Data collection

Philips PW1100 updated by Stoe diffractometer	Rint = 0.000
Radiation source: fine-focus sealed tube	θmax = 27.1°, θmin = 2.4°
Planar graphite monochromator	h = −9→9
ω scan	k = −11→11
4817 measured reflections	l = 0→21
4817 independent reflections	3 standard reflections every 240 min
2867 reflections with I > 2σ(I)	intensity decay: 1.6%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.045	H-atom parameters constrained
wR(F^2) = 0.130	Calculated w = 1/[σ^2(Fo^2) + (0.0666P)^2 + 0.2951P] where P = (Fo^2 + 2Fc^2)/3
S = 0.96	(Δ/σ)max = 0.001
4817 reflections	Δρmax = 0.23 e Å^−3
324 parameters	Δρmin = −0.40 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.024 (2)

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

	x	y	z	Uiso*/Ueq
S11	0.21921 (10)	0.27663 (8)	0.33909 (4)	0.0647 (2)
O11	0.0264 (2)	0.34324 (18)	0.11951 (9)	0.0504 (4)
O21	0.0043 (4)	0.1850 (3)	−0.06115 (13)	0.1082 (9)
O31	−0.1266 (4)	0.4076 (3)	−0.02124 (13)	0.0953 (8)
N11	0.0325 (3)	0.5080 (2)	0.24460 (11)	0.0497 (5)
N21	−0.0284 (4)	0.2809 (4)	−0.01048 (14)	0.0752 (7)
C11	0.1156 (3)	0.3611 (3)	0.25642 (13)	0.0452 (5)
C21	0.1175 (3)	0.2720 (3)	0.18686 (13)	0.0447 (5)
C31	0.1979 (3)	0.1264 (3)	0.17305 (15)	0.0549 (6)
H31	0.2673	0.0552	0.2093	0.056 (7)*
C41	0.1572 (4)	0.1031 (3)	0.09438 (16)	0.0610 (7)
H41	0.1928	0.0144	0.0679	0.076 (9)*
C51	0.0556 (3)	0.2366 (3)	0.06539 (14)	0.0542 (6)
C61	0.0075 (3)	0.6205 (3)	0.30112 (13)	0.0462 (5)
C71	0.0361 (3)	0.7618 (3)	0.27598 (16)	0.0549 (6)
H71	0.0743	0.7804	0.2237	0.063 (8)*
C81	0.0073 (4)	0.8744 (3)	0.32914 (19)	0.0658 (7)
H81	0.0253	0.9693	0.3122	0.079 (9)*
C91	−0.0474 (4)	0.8482 (3)	0.40652 (18)	0.0689 (8)
H91	−0.0646	0.9244	0.4421	0.088 (10)*
C101	−0.0770 (4)	0.7080 (3)	0.43142 (17)	0.0672 (7)
H101	−0.1152	0.6903	0.4838	0.083 (9)*
C111	−0.0502 (3)	0.5937 (3)	0.37883 (14)	0.0546 (6)
H111	−0.0709	0.4996	0.3957	0.073 (8)*
S12	0.39910 (11)	0.27191 (8)	0.84184 (4)	0.0644 (2)
O12	0.5573 (2)	0.34089 (16)	0.61883 (9)	0.0458 (4)
O22	0.6802 (3)	0.4056 (2)	0.47566 (12)	0.0782 (6)
O32	0.6581 (3)	0.1884 (3)	0.43507 (12)	0.0938 (7)
N12	0.4644 (3)	0.5031 (2)	0.74601 (11)	0.0493 (5)
N22	0.6444 (3)	0.2818 (3)	0.48642 (13)	0.0604 (6)
C12	0.4568 (3)	0.3569 (2)	0.75771 (13)	0.0435 (5)
C22	0.5003 (3)	0.2701 (2)	0.68692 (13)	0.0425 (5)
C32	0.4920 (3)	0.1274 (3)	0.67207 (14)	0.0498 (6)
H32	0.4567	0.0571	0.7083	0.056 (7)*
C42	0.5465 (3)	0.1053 (3)	0.59205 (14)	0.0537 (6)
H42	0.5556	0.0183	0.5647	0.053 (7)*
C52	0.5826 (3)	0.2372 (3)	0.56351 (13)	0.0472 (5)
C62	0.4331 (3)	0.6144 (2)	0.80357 (13)	0.0456 (5)
C72	0.3309 (3)	0.7584 (3)	0.77938 (15)	0.0528 (6)
H72	0.2809	0.7781	0.7283	0.063 (8)*
C82	0.3054 (4)	0.8707 (3)	0.83236 (17)	0.0613 (7)
H82	0.2375	0.9669	0.8170	0.077 (9)*
C92	0.3793 (4)	0.8418 (3)	0.90794 (17)	0.0655 (7)
H92	0.3609	0.9184	0.9434	0.070 (8)*
C102	0.4807 (4)	0.6995 (3)	0.93123 (16)	0.0648 (7)
H102	0.5301	0.6805	0.9824	0.068 (8)*
C112	0.5093 (3)	0.5849 (3)	0.87898 (14)	0.0537 (6)
H112	0.5789	0.4894	0.8944	0.040 (6)*
H11	−0.0072	0.5378	0.1921	0.066 (8)*
H12	0.4792	0.5364	0.6926	0.073 (8)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S11	0.0773 (5)	0.0611 (4)	0.0446 (4)	0.0048 (3)	−0.0089 (3)	0.0061 (3)
O11	0.0546 (9)	0.0556 (10)	0.0439 (9)	−0.0205 (7)	−0.0048 (7)	0.0056 (7)
O21	0.138 (2)	0.155 (2)	0.0524 (12)	−0.0713 (19)	−0.0039 (13)	−0.0224 (15)
O31	0.1173 (19)	0.1049 (19)	0.0769 (15)	−0.0594 (16)	−0.0457 (13)	0.0325 (13)
N11	0.0580 (12)	0.0486 (11)	0.0407 (10)	−0.0093 (9)	−0.0086 (9)	0.0040 (8)
N21	0.0883 (18)	0.108 (2)	0.0479 (13)	−0.0628 (17)	−0.0074 (12)	0.0078 (14)
C11	0.0413 (12)	0.0495 (13)	0.0430 (12)	−0.0097 (10)	0.0023 (9)	0.0054 (10)
C21	0.0439 (12)	0.0505 (13)	0.0405 (11)	−0.0155 (10)	−0.0012 (9)	0.0069 (10)
C31	0.0529 (14)	0.0544 (15)	0.0569 (15)	−0.0120 (11)	0.0007 (11)	−0.0012 (12)
C41	0.0579 (15)	0.0664 (17)	0.0619 (16)	−0.0185 (13)	0.0090 (12)	−0.0158 (14)
C51	0.0565 (15)	0.0718 (17)	0.0437 (13)	−0.0339 (13)	0.0020 (11)	−0.0039 (12)
C61	0.0415 (12)	0.0477 (13)	0.0473 (13)	−0.0070 (9)	−0.0072 (9)	0.0029 (10)
C71	0.0527 (14)	0.0539 (15)	0.0572 (15)	−0.0117 (11)	−0.0065 (11)	0.0038 (12)
C81	0.0589 (16)	0.0517 (16)	0.086 (2)	−0.0098 (12)	−0.0157 (14)	−0.0041 (14)
C91	0.0594 (16)	0.0712 (19)	0.0717 (19)	0.0014 (14)	−0.0186 (14)	−0.0223 (16)
C101	0.0587 (16)	0.085 (2)	0.0480 (15)	0.0046 (14)	−0.0042 (12)	−0.0042 (14)
C111	0.0528 (14)	0.0563 (15)	0.0508 (14)	−0.0064 (11)	0.0007 (11)	0.0036 (12)
S12	0.0957 (5)	0.0594 (4)	0.0460 (4)	−0.0368 (4)	0.0006 (3)	0.0053 (3)
O12	0.0497 (9)	0.0416 (9)	0.0445 (9)	−0.0085 (7)	−0.0030 (7)	0.0033 (7)
O22	0.0798 (14)	0.0716 (14)	0.0740 (13)	−0.0069 (10)	0.0176 (10)	0.0188 (11)
O32	0.1171 (19)	0.1118 (18)	0.0523 (12)	−0.0225 (14)	0.0095 (11)	−0.0193 (13)
N12	0.0628 (12)	0.0426 (11)	0.0422 (10)	−0.0128 (9)	0.0025 (9)	0.0017 (8)
N22	0.0557 (13)	0.0706 (15)	0.0473 (12)	−0.0013 (11)	0.0002 (9)	0.0044 (11)
C12	0.0439 (12)	0.0438 (12)	0.0439 (12)	−0.0137 (9)	−0.0056 (9)	0.0030 (10)
C22	0.0406 (12)	0.0432 (12)	0.0427 (12)	−0.0097 (9)	−0.0073 (9)	0.0072 (9)
C32	0.0557 (14)	0.0467 (13)	0.0500 (13)	−0.0190 (11)	−0.0133 (11)	0.0060 (10)
C42	0.0621 (15)	0.0472 (14)	0.0531 (14)	−0.0135 (11)	−0.0117 (11)	−0.0056 (11)
C52	0.0441 (12)	0.0529 (14)	0.0422 (12)	−0.0066 (10)	−0.0088 (9)	0.0011 (10)
C62	0.0470 (13)	0.0449 (13)	0.0473 (13)	−0.0166 (10)	0.0051 (10)	−0.0004 (10)
C72	0.0505 (14)	0.0507 (14)	0.0568 (15)	−0.0130 (10)	0.0028 (11)	0.0034 (11)
C82	0.0609 (16)	0.0484 (15)	0.0749 (18)	−0.0140 (12)	0.0171 (13)	−0.0071 (13)
C92	0.0754 (18)	0.0635 (17)	0.0669 (18)	−0.0320 (14)	0.0271 (14)	−0.0235 (15)
C102	0.0808 (19)	0.0753 (19)	0.0483 (15)	−0.0385 (16)	0.0033 (13)	−0.0042 (14)
C112	0.0613 (15)	0.0503 (14)	0.0516 (14)	−0.0185 (12)	−0.0034 (11)	0.0022 (11)

Geometric parameters (Å, º)

S11—C11	1.655 (2)	S12—C12	1.655 (2)
O11—C51	1.351 (3)	O12—C52	1.347 (3)
O11—C21	1.374 (3)	O12—C22	1.377 (2)
O21—N21	1.239 (4)	O22—N22	1.219 (3)
O31—N21	1.223 (4)	O32—N22	1.236 (3)
N11—C11	1.344 (3)	N12—C12	1.348 (3)
N11—C61	1.419 (3)	N12—C62	1.422 (3)
N21—C51	1.421 (3)	N22—C52	1.424 (3)
C11—C21	1.461 (3)	C12—C22	1.458 (3)
C21—C31	1.359 (3)	C22—C32	1.356 (3)
C31—C41	1.398 (4)	C32—C42	1.403 (3)
C41—C51	1.345 (4)	C42—C52	1.345 (3)
C61—C111	1.383 (3)	C62—C112	1.380 (3)
C61—C71	1.389 (3)	C62—C72	1.398 (3)
C71—C81	1.380 (4)	C72—C82	1.376 (4)
C81—C91	1.370 (4)	C82—C92	1.376 (4)
C91—C101	1.381 (4)	C92—C102	1.380 (4)
C101—C111	1.386 (4)	C102—C112	1.383 (4)
C51—O11—C21	104.58 (18)	C52—O12—C22	104.90 (17)
C11—N11—C61	127.37 (19)	C12—N12—C62	127.53 (19)
O31—N21—O21	124.9 (3)	O22—N22—O32	125.1 (2)
O31—N21—C51	119.0 (3)	O22—N22—C52	119.2 (2)
O21—N21—C51	116.1 (3)	O32—N22—C52	115.8 (2)
N11—C11—C21	114.81 (19)	N12—C12—C22	114.54 (19)
N11—C11—S11	126.59 (18)	N12—C12—S12	126.66 (18)
C21—C11—S11	118.56 (17)	C22—C12—S12	118.78 (16)
C31—C21—O11	109.9 (2)	C32—C22—O12	109.7 (2)
C31—C21—C11	132.4 (2)	C32—C22—C12	132.5 (2)
O11—C21—C11	117.65 (19)	O12—C22—C12	117.75 (18)
C21—C31—C41	107.5 (2)	C22—C32—C42	107.5 (2)
C51—C41—C31	105.0 (2)	C52—C42—C32	105.0 (2)
C41—C51—O11	113.0 (2)	C42—C52—O12	112.9 (2)
C41—C51—N21	130.9 (3)	C42—C52—N22	130.7 (2)
O11—C51—N21	116.1 (3)	O12—C52—N22	116.4 (2)
C111—C61—C71	120.0 (2)	C112—C62—C72	120.8 (2)
C111—C61—N11	121.6 (2)	C112—C62—N12	121.7 (2)
C71—C61—N11	118.4 (2)	C72—C62—N12	117.4 (2)
C81—C71—C61	119.5 (3)	C82—C72—C62	118.9 (2)
C91—C81—C71	120.9 (3)	C72—C82—C92	120.6 (3)
C81—C91—C101	119.6 (3)	C82—C92—C102	120.1 (3)
C91—C101—C111	120.4 (3)	C92—C102—C112	120.5 (3)
C61—C111—C101	119.6 (2)	C62—C112—C102	119.1 (2)
C61—N11—C11—C21	179.0 (2)	C62—N12—C12—C22	−178.57 (19)
C61—N11—C11—S11	−3.4 (3)	C62—N12—C12—S12	3.1 (3)
C51—O11—C21—C31	−0.3 (2)	C52—O12—C22—C32	0.0 (2)
C51—O11—C21—C11	178.32 (18)	C52—O12—C22—C12	−178.40 (17)
N11—C11—C21—C31	174.3 (2)	N12—C12—C22—C32	−173.1 (2)
S11—C11—C21—C31	−3.5 (3)	S12—C12—C22—C32	5.4 (3)
N11—C11—C21—O11	−4.0 (3)	N12—C12—C22—O12	4.9 (3)
S11—C11—C21—O11	178.27 (15)	S12—C12—C22—O12	−176.63 (14)
O11—C21—C31—C41	0.0 (3)	O12—C22—C32—C42	0.4 (2)
C11—C21—C31—C41	−178.4 (2)	C12—C22—C32—C42	178.4 (2)
C21—C31—C41—C51	0.4 (3)	C22—C32—C42—C52	−0.6 (3)
C31—C41—C51—O11	−0.6 (3)	C32—C42—C52—O12	0.6 (3)
C31—C41—C51—N21	−178.5 (2)	C32—C42—C52—N22	179.5 (2)
C21—O11—C51—C41	0.6 (2)	C22—O12—C52—C42	−0.4 (2)
C21—O11—C51—N21	178.85 (19)	C22—O12—C52—N22	−179.41 (18)
O31—N21—C51—C41	174.7 (3)	O22—N22—C52—C42	−175.0 (2)
O21—N21—C51—C41	−4.9 (4)	O32—N22—C52—C42	4.7 (4)
O31—N21—C51—O11	−3.2 (3)	O22—N22—C52—O12	3.9 (3)
O21—N21—C51—O11	177.3 (2)	O32—N22—C52—O12	−176.5 (2)
C11—N11—C61—C111	−44.6 (3)	C12—N12—C62—C112	45.7 (3)
C11—N11—C61—C71	137.8 (2)	C12—N12—C62—C72	−138.1 (2)
C111—C61—C71—C81	0.3 (3)	C112—C62—C72—C82	−0.7 (3)
N11—C61—C71—C81	178.1 (2)	N12—C62—C72—C82	−177.0 (2)
C61—C71—C81—C91	0.6 (4)	C62—C72—C82—C92	0.0 (4)
C71—C81—C91—C101	−1.0 (4)	C72—C82—C92—C102	0.2 (4)
C81—C91—C101—C111	0.5 (4)	C82—C92—C102—C112	0.2 (4)
C71—C61—C111—C101	−0.8 (3)	C72—C62—C112—C102	1.1 (3)
N11—C61—C111—C101	−178.5 (2)	N12—C62—C112—C102	177.2 (2)
C91—C101—C111—C61	0.4 (4)	C92—C102—C112—C62	−0.8 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N11—H11···O11	0.94	2.18	2.664 (2)	111
N12—H12···O12	0.94	2.20	2.661 (2)	110
C111—H111···O22^i	0.93	2.54	3.271 (3)	136
C112—H112···O31^ii	0.93	2.58	3.267 (4)	131

Symmetry codes: (i) x−1, y, z; (ii) x+1, y, z+1.