(E)-5-[(4-Nitro­phenyl­hydrazono)­phenyl­acetyl]-3-phenyl­isoxazole

The title compound, C₂₃H₁₆N₄O₄, can be considered as consisting of two connected fragments: a nitro­phenyl­hydrazone moiety, which assumes an E configuration, and an isoxazole moiety. In this latter fragment, the weak π-electron delocalization shortens the carbonyl–isoxazole O...O distance [2.643 (2) Å] to less than the van der Waals radii sum.

S1. Comment

As part of our investigation into the participation of vicinal groups in the bromination reaction of isoxazole compounds to form bis-heterocyclic spirans, we succeeded in obtaining single crystals, suitable for X-ray crystallography, of the title compound, (I). This compound was formed during the electrophilic bromination of 3-phenyl-p-nitrophenylhydrazone-5-phenacylisoxazole in chloroform. The formation of (I) can be ascribed to a hydrolytic process resulting from the presence of moisture in the reaction medium. \scheme

The structure of (I) is shown in Fig. 1, and selected bond lengths and angles are listed in Table 1. In the following discussion, the molecule will be considered in two fragments: the nitrophenylhydrazone moiety and the isoxazole moiety.

It is remarkable that the E isomer for the nitrophenylhydrazone derivative was formed preferentially over the Z isomer since the latter would almost certainly feature an NH···OC intramolecular hydrogen bond. In (I), the E isomer is stabilized by an intermolecular hydrogen bond involving atoms N2, C23 and C2. The geometric parameters are listed in Table 2. Atoms N3 and O2 are involved in two intermolecular hydrogen interactions that stabilize the molecular packing, N3 with O4ⁱ and C7 with O2ⁱⁱ; the geometric parameters are listed in Table 2 [symmetry codes: (i) 1/2 + x, 1/2 − y, z − 1/2; (ii) x − 1, y, z].

The phenylhydrazone fragment is almost planar; geometric calculations show that the maximum distance from the mean plane is 0.077 (2) Å for O4. All geometric parameters concerning the nitrophenylhydrazone fragment of the molecule agree with the values found in the literature for similar compounds (Willey & Drew, 1983; Drew & Willey, 1982; Stankovic et al., 1991; Whitaker, 1987) without an intramolecular hydrogen bond (NH···OC).

In the second fragment, the isoxazole ring is nearly planar; the maximum deviation from the mean plane is 0.010 (2) Å for N1. The angle between the nitrophenylhydrazone plane and the isoxazole plane is 32.94 (6)°, and the phenyl ring is twisted a further 20.48 (8)° from the isoxazole plane. The mutual orientation of the aromatic ring and the isoxazole moiety is due to the presence of an intramolecular hydrogen bond interaction involving N1 and C17 (see Table 2). The values of the C2—C1, C1—C4 and C4—O2 bond lengths (Table 1) show a weak π-electron delocalization with respect to the compound reported by Sundaralingam & Jeffrey (1962). Other geometric parameters are in good agreement with those reported in the literature (Staskun et al., 1991; Smith et al., 1991).

The packing is mainly determined by normal van der Waals interactions and two intermolecular hydrogen bonds involving the N3 and O2 atoms, as discussed above. As can be seen in Fig. 2, the molecules are packed in a head-tail fashion along the a axis.

S2. Experimental

3-Phenyl-p-nitrophenylhydrazone-5-phenacylisoxazole (1 mmol) was dissolved in hot chloroform (40 ml). Br₂ (2 mmol) was added with continuous stirring and the mixture refluxed for 4 h. During the reaction a powder began to precipitate. The solid was removed by filtration and the organic phase was separated and evaporated to dryness. The residue, (I), was crystallized from acetone at room temperature (m.p. 422–424 K). Single crystals of (I) suitable for X-ray diffraction analysis were grown from a CH2Cl2/CH3OH mixture (~1:2 v/v).

Computing details

Data collection: P3/V (Siemens,1989); cell refinement: P3/V; data reduction: SHELXTL-Plus (Sheldrick, 1990); program(s) used to solve structure: ??; program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XPW (Siemens, 1996); software used to prepare material for publication: locally modified PARST97 (Nardelli, 1995) and SHELXL97.

Figures

	Fig. 1. A view of (I) showing the atomic numbering scheme and with displacement ellipsoids at the 50% probability level. H atoms are drawn as circles of arbitrary radii.
	Fig. 2. A view of the molecular packing in (I) along the a axis.

(E)-5-[(4-Nitrophenylhydrazono)phenylacetyl]-3-phenylisoxazole

Crystal data

C23H16N4O4	F(000) = 856
Mr = 412.40	Dx = 1.393 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 5.787 (1) Å	Cell parameters from 41 reflections
b = 29.089 (3) Å	θ = 12–28°
c = 11.881 (1) Å	µ = 0.10 mm^−1
β = 100.49 (1)°	T = 293 K
V = 1966.6 (4) Å^3	Prismatic, colourless
Z = 4	0.25 × 0.18 × 0.12 mm

Data collection

Siemens R3m/V diffractometer	Rint = 0.013
Radiation source: fine-focus sealed tube	θmax = 24.5°, θmin = 1.9°
Graphite monochromator	h = −1→6
ω/2θ scans	k = −7→34
3739 measured reflections	l = −13→13
3301 independent reflections	3 standard reflections every 197 reflections
1899 reflections with I > 2σ(I)	intensity decay: 1.3%

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)] = 0.034	H-atom parameters constrained
wR(F^2) = 0.079	Calculated w = 1/[σ^2(Fo^2) + (0.1383P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.84	(Δ/σ)max = 0.001
3301 reflections	Δρmax = 0.23 e Å^−3
282 parameters	Δρmin = −0.19 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001Fc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.085 (7)

Special details

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 on F² for ALL reflections except for 1 with very negative F² or flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F².

Reflection intensities were evaluated by profile fitting of a 96-steps peak scan among 2θ shells (Diamond, 1969) and then corrected for Lorentz polarization effects. Standard uncertainties σ(I) were estimated from counting statistics. All non-H atoms were refined anisotropically. H atoms were located on idealized positions and allowed to ride on their parent C atoms, with a common isotropic displacement parameter (U_iso = 0.08 Ų).

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

	x	y	z	Uiso*/Ueq
O1	0.8535 (2)	0.07201 (5)	0.88060 (11)	0.0600 (4)
N1	0.8998 (3)	0.05888 (6)	0.99588 (14)	0.0607 (5)
C3	0.6952 (3)	0.05817 (6)	1.02930 (15)	0.0455 (5)
C2	0.5123 (3)	0.07198 (6)	0.93893 (15)	0.0473 (5)
H2	0.3532	0.0749	0.9411	0.069*
C1	0.6201 (3)	0.08003 (6)	0.84946 (16)	0.0457 (5)
C4	0.5523 (3)	0.09232 (6)	0.72602 (16)	0.0490 (5)
O2	0.6775 (2)	0.07956 (5)	0.65995 (11)	0.0693 (4)
C5	0.3423 (3)	0.12078 (6)	0.68579 (15)	0.0436 (5)
C6	0.2777 (3)	0.13099 (6)	0.56121 (14)	0.0448 (5)
C7	0.0650 (3)	0.11653 (7)	0.49840 (17)	0.0552 (5)
H7	−0.0407	0.1006	0.5342	0.069*
C8	0.0098 (4)	0.12576 (8)	0.38234 (18)	0.0706 (6)
H8	−0.1334	0.1162	0.3401	0.069*
C9	0.1674 (5)	0.14915 (8)	0.32957 (18)	0.0773 (7)
H9	0.1304	0.1551	0.2514	0.069*
C10	0.3775 (4)	0.16377 (8)	0.39078 (18)	0.0713 (6)
H10	0.4820	0.1800	0.3547	0.069*
C11	0.4334 (3)	0.15449 (7)	0.50557 (17)	0.0568 (5)
H11	0.5775	0.1640	0.5469	0.069*
N2	0.2370 (2)	0.13680 (5)	0.76546 (12)	0.0452 (4)
N3	0.0546 (2)	0.16550 (5)	0.73490 (12)	0.0481 (4)
H3	0.0097	0.1727	0.6641	0.069*
C12	0.6840 (3)	0.04363 (6)	1.14708 (15)	0.0446 (5)
C13	0.4950 (3)	0.05505 (7)	1.19838 (17)	0.0582 (5)
H13	0.3707	0.0719	1.1577	0.069*
C14	0.4895 (3)	0.04160 (8)	1.30928 (18)	0.0701 (6)
H14	0.3631	0.0498	1.3434	0.069*
C15	0.6713 (4)	0.01607 (8)	1.36954 (18)	0.0698 (6)
H15	0.6681	0.0071	1.4444	0.069*
C16	0.8579 (4)	0.00378 (7)	1.31875 (18)	0.0645 (6)
H16	0.9796	−0.0139	1.3589	0.069*
C17	0.8645 (3)	0.01749 (6)	1.20877 (17)	0.0568 (5)
H17	0.9916	0.0092	1.1752	0.069*
C18	−0.0614 (3)	0.18357 (6)	0.81716 (14)	0.0418 (4)
C19	−0.2554 (3)	0.21144 (6)	0.78165 (15)	0.0465 (5)
H19	−0.3013	0.2182	0.7043	0.069*
C20	−0.3811 (3)	0.22922 (6)	0.85954 (15)	0.0495 (5)
H20	−0.5119	0.2477	0.8356	0.069*
C21	−0.3090 (3)	0.21899 (6)	0.97339 (16)	0.0529 (5)
N4	−0.4360 (4)	0.23844 (7)	1.05652 (16)	0.0741 (5)
O3	−0.3765 (4)	0.22739 (7)	1.15683 (14)	0.1352 (8)
O4	−0.5933 (3)	0.26640 (6)	1.02438 (13)	0.0821 (5)
C22	−0.1163 (4)	0.19186 (8)	1.00953 (17)	0.0709 (7)
H22	−0.0705	0.1854	1.0870	0.069*
C23	0.0090 (4)	0.17408 (7)	0.93264 (15)	0.0619 (6)
H23	0.1402	0.1558	0.9575	0.069*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0406 (8)	0.0772 (10)	0.0642 (9)	0.0087 (7)	0.0147 (7)	0.0088 (7)
N1	0.0446 (9)	0.0767 (13)	0.0606 (11)	0.0077 (9)	0.0089 (8)	0.0121 (9)
C3	0.0391 (10)	0.0430 (11)	0.0542 (12)	0.0012 (9)	0.0079 (9)	−0.0037 (9)
C2	0.0366 (10)	0.0510 (12)	0.0547 (12)	0.0020 (9)	0.0091 (9)	−0.0011 (10)
C1	0.0371 (10)	0.0486 (12)	0.0520 (12)	0.0039 (9)	0.0093 (9)	−0.0005 (9)
C4	0.0447 (11)	0.0508 (12)	0.0556 (13)	−0.0002 (9)	0.0195 (10)	−0.0037 (10)
O2	0.0635 (9)	0.0859 (11)	0.0654 (10)	0.0203 (8)	0.0305 (8)	0.0047 (8)
C5	0.0418 (11)	0.0450 (11)	0.0467 (12)	−0.0040 (9)	0.0154 (9)	−0.0034 (9)
C6	0.0436 (11)	0.0487 (12)	0.0444 (11)	0.0020 (9)	0.0137 (9)	−0.0036 (9)
C7	0.0523 (12)	0.0602 (14)	0.0542 (13)	0.0006 (10)	0.0130 (10)	−0.0053 (10)
C8	0.0658 (14)	0.0855 (17)	0.0564 (15)	0.0151 (13)	0.0007 (12)	−0.0108 (13)
C9	0.0954 (19)	0.0930 (19)	0.0436 (14)	0.0313 (16)	0.0130 (14)	0.0114 (12)
C10	0.0791 (17)	0.0777 (17)	0.0637 (15)	0.0131 (14)	0.0303 (13)	0.0214 (12)
C11	0.0551 (12)	0.0620 (14)	0.0558 (13)	−0.0015 (11)	0.0172 (10)	0.0017 (11)
N2	0.0434 (9)	0.0446 (9)	0.0495 (10)	0.0014 (8)	0.0135 (7)	−0.0017 (8)
N3	0.0514 (9)	0.0534 (10)	0.0421 (9)	0.0092 (8)	0.0151 (8)	0.0016 (7)
C12	0.0383 (10)	0.0434 (11)	0.0498 (11)	−0.0003 (9)	0.0021 (9)	−0.0019 (9)
C13	0.0450 (11)	0.0701 (15)	0.0588 (13)	0.0076 (10)	0.0075 (10)	0.0109 (11)
C14	0.0534 (13)	0.0938 (18)	0.0658 (15)	0.0083 (12)	0.0179 (11)	0.0132 (13)
C15	0.0632 (14)	0.0868 (17)	0.0587 (14)	−0.0053 (13)	0.0091 (12)	0.0165 (12)
C16	0.0563 (13)	0.0659 (15)	0.0675 (15)	0.0069 (11)	0.0018 (11)	0.0135 (12)
C17	0.0506 (12)	0.0556 (13)	0.0635 (14)	0.0075 (10)	0.0083 (10)	0.0000 (11)
C18	0.0474 (11)	0.0376 (11)	0.0424 (11)	−0.0004 (9)	0.0138 (9)	−0.0046 (8)
C19	0.0530 (11)	0.0506 (12)	0.0376 (11)	0.0025 (10)	0.0129 (9)	0.0017 (9)
C20	0.0536 (11)	0.0472 (12)	0.0488 (12)	0.0041 (10)	0.0125 (10)	−0.0046 (9)
C21	0.0684 (13)	0.0526 (13)	0.0406 (11)	0.0079 (11)	0.0176 (10)	−0.0081 (10)
N4	0.0978 (15)	0.0801 (14)	0.0483 (12)	0.0196 (12)	0.0234 (11)	−0.0102 (10)
O3	0.189 (2)	0.174 (2)	0.0517 (11)	0.0875 (16)	0.0472 (12)	0.0072 (12)
O4	0.0861 (11)	0.0916 (12)	0.0725 (11)	0.0268 (10)	0.0250 (9)	−0.0153 (9)
C22	0.0965 (17)	0.0796 (16)	0.0357 (12)	0.0288 (14)	0.0096 (12)	−0.0015 (11)
C23	0.0724 (14)	0.0708 (15)	0.0414 (12)	0.0234 (12)	0.0070 (10)	−0.0022 (10)

Geometric parameters (Å, º)

O1—C1	1.354 (2)	N2—N3	1.343 (2)
O1—N1	1.400 (2)	N3—C18	1.386 (2)
N1—C3	1.316 (2)	C12—C13	1.386 (2)
C3—C2	1.421 (2)	C12—C17	1.388 (2)
C3—C12	1.475 (2)	C13—C14	1.380 (3)
C2—C1	1.347 (2)	C14—C15	1.377 (3)
C1—C4	1.491 (2)	C15—C16	1.377 (3)
C4—O2	1.219 (2)	C16—C17	1.373 (3)
C4—C5	1.476 (2)	C18—C23	1.386 (2)
C5—N2	1.302 (2)	C18—C19	1.387 (2)
C5—C6	1.489 (2)	C19—C20	1.377 (2)
C6—C7	1.383 (2)	C20—C21	1.374 (2)
C6—C11	1.390 (2)	C21—C22	1.370 (3)
C7—C8	1.384 (2)	C21—N4	1.449 (2)
C8—C9	1.377 (3)	N4—O3	1.222 (2)
C9—C10	1.366 (3)	N4—O4	1.229 (2)
C10—C11	1.370 (3)	C22—C23	1.367 (2)
C1—O1—N1	108.5 (1)	C5—N2—N3	118.3 (2)
C3—N1—O1	106.1 (2)	N2—N3—C18	120.2 (2)
N1—C3—C2	110.8 (2)	C13—C12—C17	118.51 (18)
N1—C3—C12	119.2 (2)	C13—C12—C3	121.55 (16)
C2—C3—C12	129.98 (15)	C17—C12—C3	119.93 (17)
C1—C2—C3	104.9 (2)	C14—C13—C12	120.60 (18)
C2—C1—O1	109.7 (2)	C15—C14—C13	120.1 (2)
C2—C1—C4	137.83 (17)	C16—C15—C14	119.9 (2)
O1—C1—C4	112.4 (2)	C17—C16—C15	120.09 (19)
O2—C4—C5	120.9 (2)	C16—C17—C12	120.85 (19)
O2—C4—C1	118.7 (2)	C23—C18—N3	122.0 (2)
C5—C4—C1	120.44 (16)	C23—C18—C19	119.57 (17)
N2—C5—C4	115.6 (2)	N3—C18—C19	118.5 (2)
N2—C5—C6	125.8 (2)	C20—C19—C18	120.80 (17)
C4—C5—C6	118.47 (15)	C21—C20—C19	118.53 (18)
C7—C6—C11	118.87 (17)	C22—C21—C20	121.15 (18)
C7—C6—C5	120.87 (17)	C22—C21—N4	119.8 (2)
C11—C6—C5	120.24 (16)	C20—C21—N4	119.1 (2)
C6—C7—C8	119.99 (19)	O3—N4—O4	122.6 (2)
C9—C8—C7	119.8 (2)	O3—N4—C21	118.3 (2)
C10—C9—C8	120.7 (2)	O4—N4—C21	119.1 (2)
C9—C10—C11	119.6 (2)	C23—C22—C21	120.60 (19)
C10—C11—C6	120.95 (19)	C22—C23—C18	119.34 (19)
C1—O1—N1—C3	1.7 (2)	C6—C5—N2—N3	−0.6 (3)
O1—N1—C3—C2	−1.7 (2)	C5—N2—N3—C18	−179.58 (15)
O1—N1—C3—C12	177.56 (14)	N1—C3—C12—C13	160.04 (19)
N1—C3—C2—C1	1.2 (2)	C2—C3—C12—C13	−20.8 (3)
C12—C3—C2—C1	−178.03 (17)	N1—C3—C12—C17	−20.6 (3)
C3—C2—C1—O1	−0.1 (2)	C2—C3—C12—C17	158.54 (18)
C3—C2—C1—C4	175.2 (2)	C17—C12—C13—C14	1.5 (3)
N1—O1—C1—C2	−1.0 (2)	C3—C12—C13—C14	−179.14 (18)
N1—O1—C1—C4	−177.53 (14)	C12—C13—C14—C15	−0.9 (3)
C2—C1—C4—O2	−150.8 (2)	C13—C14—C15—C16	−0.4 (3)
O1—C1—C4—O2	24.3 (2)	C14—C15—C16—C17	0.9 (3)
C2—C1—C4—C5	31.3 (3)	C15—C16—C17—C12	−0.3 (3)
O1—C1—C4—C5	−153.52 (16)	C13—C12—C17—C16	−0.9 (3)
O2—C4—C5—N2	−172.44 (17)	C3—C12—C17—C16	179.71 (17)
C1—C4—C5—N2	5.4 (2)	N2—N3—C18—C23	2.0 (2)
O2—C4—C5—C6	4.0 (3)	N2—N3—C18—C19	−177.16 (14)
C1—C4—C5—C6	−178.22 (16)	C23—C18—C19—C20	−1.0 (3)
N2—C5—C6—C7	−65.6 (2)	N3—C18—C19—C20	178.14 (16)
C4—C5—C6—C7	118.38 (19)	C18—C19—C20—C21	0.4 (3)
N2—C5—C6—C11	115.8 (2)	C19—C20—C21—C22	0.2 (3)
C4—C5—C6—C11	−60.3 (2)	C19—C20—C21—N4	178.41 (17)
C11—C6—C7—C8	−0.4 (3)	C22—C21—N4—O3	−5.0 (3)
C5—C6—C7—C8	−179.02 (18)	C20—C21—N4—O3	176.8 (2)
C6—C7—C8—C9	0.3 (3)	C22—C21—N4—O4	172.6 (2)
C7—C8—C9—C10	−0.6 (3)	C20—C21—N4—O4	−5.6 (3)
C8—C9—C10—C11	0.9 (3)	C20—C21—C22—C23	−0.2 (3)
C9—C10—C11—C6	−1.0 (3)	N4—C21—C22—C23	−178.45 (19)
C7—C6—C11—C10	0.7 (3)	C21—C22—C23—C18	−0.3 (3)
C5—C6—C11—C10	179.38 (18)	N3—C18—C23—C22	−178.17 (18)
C4—C5—N2—N3	175.49 (14)	C19—C18—C23—C22	0.9 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2···N2	0.93	2.75	3.024 (2)	98
C23—H23···N2	0.93	2.51	2.796 (2)	98
C11—H11···O2	0.93	2.81	3.028 (2)	94
C17—H17···N1	0.93	2.55	2.842 (3)	99
C20—H20···O4	0.93	2.44	2.718 (2)	98
N3—H3···O4^i	0.86	2.43	3.183 (2)	147
C7—H7···O2^ii	0.93	2.48	3.382 (2)	163

Symmetry codes: (i) x+1/2, −y+1/2, z−1/2; (ii) x−1, y, z.