(Z)-Methyl 3-(4-ethoxy­anilino)but-2-enoate

The title compound, C₁₃H₁₇NO₃, was synthesized from methyl 3-oxobutanoate and 4-ethoxy­benzenamine using a catalytic amount of InBr₃ under solvent-free conditions. The 3-amino­but-2-enoic acid methyl ester group is planar and forms a dihedral angle of 83.4 (1)° with the benzene ring. The eth­oxy group is slightly twisted away from the benzene ring [dihedral angle = 13.8 (1)°]. An intra­molecular N—H...O hydrogen bond generating an S(6) ring is observed. Mol­ecules are linked into a chain along the b axis by inter­molecular C—H...O hydrogen bonding.

Key indicators

• Single-crystal X-ray study
• T = 294 K
• Mean [sigma](C-C)= 0.003 Å
• R factor = 0.042
• wR factor = 0.137
• Data-to-parameter ratio = 16.6

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S1. Comment

β-Enamino esters are useful precursors for the preparation of biologically active compounds such as β-enamino acids, γ-enamino alcohols or β-enamino esters (Lubell et al., 1991; Bartoli et al., 1994; Cimarelli et al., 1994; Cimarelli & Palmieri, 1996). Therefore, many synthetic methods have been developed for the preparation of these compounds (Greenhill, 1977; Elassar et al., 2003; Michael et al., 1999). As part of our program on developing new environmental friendly methodologies for the preparation of β-enamino compounds, we have synthesized the title compound (Fig.1). We report here the crystal structure of it.

In the title molecule, the 3-amino-but-2-enoic acid methyl ester group is planar (r.m.s. deviation 0.045 Å) and it forms a dihedral angle of 83.4 (1)° with the benzene ring. The ethoxy group is slightly twisted away from the benzene ring [dihedral angle 13.8 (1)°]. An intramolecular N1—H1···O2 hydrogen bond generating an S(6) ring is observed. The N1—C9 bond length [1.341 (2) Å] is shorter than the N1—C1 [1.435 (2) Å] bond length, indicating electron delocalization.

The molecules are linked into a chain along the b axis by intermolecular C—H···O hydrogen bonds (Fig. 2).

Related literature

For general background on β-enamino esters, see: Bartoli et al. (1994); Cimarelli & Palmieri (1996); Cimarelli et al. (1994); Elassar & El-Khair (2003); Greenhill (1977); Lubell et al. (1991); Michael et al. (1999); Paola et al. (2000); Rybarczyk-Pirek & Grabowski (2002); Yunus et al. (2008).

S2. Experimental

A mixture of the methyl-3-oxobutanoate (5 mmol), 4-ethoxybenzenamine (5 mmol) and InBr₃ (0.05 mmol) was stirred at room temperature for 1 h. After completion of the reaction, the reaction mixture was diluted with H₂O (10 ml) and extracted with EtOAc (210 ml). The combined organic layers were dried, concentrated, purified by column chromatography on SiO₂ with ethyl acetate-cyclohexane (2:8). Single crystals suitable for X-ray diffraction study were obtained from EtOAc-cyclohexane (1:10 v/v) by slow evaporation at room temperature.

S3. Refinement

H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with N—H = 0.86 Å, C—H = 0.93–0.97 Å, and U_iso(H) = 1.5U_eq(methyl C) or 1.2U_eq(C,N). Each methyl group was allowed to rotate freely about its C—C bond.

Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT (Bruker, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. The molecular structure of the title compound, showing 30% probability displacement ellipsoids.
	Fig. 2. A view of the molecular packing in the title compound. Hydrogen bonds are shown as dashed lines.

(Z)-Methyl 3-(4-ethoxyanilino)but-2-enoate

Crystal data

C13H17NO3	F(000) = 504
Mr = 235.28	Dx = 1.206 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 2289 reflections
a = 12.421 (2) Å	θ = 2.5–24.9°
b = 6.3372 (13) Å	µ = 0.09 mm^−1
c = 16.569 (3) Å	T = 294 K
β = 96.519 (3)°	Block, yellow
V = 1295.7 (4) Å^3	0.30 × 0.26 × 0.20 mm
Z = 4

Data collection

Bruker SMART CCD area-detector diffractometer	2628 independent reflections
Radiation source: fine-focus sealed tube	1629 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.031
ϕ and ω scans	θmax = 26.3°, θmin = 2.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −11→15
Tmin = 0.942, Tmax = 0.990	k = −7→6
6917 measured reflections	l = −20→20

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)] = 0.042	H-atom parameters constrained
wR(F^2) = 0.136	w = 1/[σ^2(Fo^2) + (0.0697P)^2 + 0.1223P] where P = (Fo^2 + 2Fc^2)/3
S = 1.00	(Δ/σ)max = 0.001
2628 reflections	Δρmax = 0.13 e Å^−3
158 parameters	Δρmin = −0.11 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.106 (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 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 > σ(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 (Ų)

	x	y	z	Uiso*/Ueq
O1	0.11751 (9)	1.2475 (2)	1.03170 (8)	0.0714 (4)
O2	0.55147 (10)	0.4131 (2)	0.90568 (7)	0.0697 (4)
O3	0.60606 (12)	0.2866 (2)	0.79053 (8)	0.0872 (5)
N1	0.39962 (11)	0.7279 (2)	0.88382 (9)	0.0654 (4)
H1	0.4403	0.6528	0.9181	0.078*
C1	0.32646 (13)	0.8715 (3)	0.91658 (9)	0.0578 (4)
C2	0.21953 (14)	0.8158 (3)	0.92064 (10)	0.0660 (5)
H2	0.1934	0.6891	0.8979	0.079*
C3	0.15124 (13)	0.9455 (3)	0.95793 (11)	0.0642 (5)
H3	0.0794	0.9067	0.9600	0.077*
C4	0.18978 (13)	1.1339 (3)	0.99243 (10)	0.0562 (4)
C5	0.29584 (13)	1.1948 (3)	0.98654 (11)	0.0621 (5)
H5	0.3216	1.3232	1.0079	0.074*
C6	0.36297 (13)	1.0624 (3)	0.94847 (10)	0.0622 (5)
H6	0.4341	1.1032	0.9444	0.075*
C7	0.15753 (16)	1.4153 (3)	1.08352 (12)	0.0747 (6)
H7A	0.1915	1.5212	1.0526	0.090*
H7B	0.2113	1.3624	1.1257	0.090*
C8	0.06476 (18)	1.5100 (4)	1.12071 (12)	0.0860 (6)
H8A	0.0129	1.5654	1.0787	0.129*
H8B	0.0908	1.6218	1.1569	0.129*
H8C	0.0309	1.4036	1.1505	0.129*
C9	0.41069 (14)	0.6995 (3)	0.80498 (10)	0.0606 (5)
C10	0.34385 (18)	0.8388 (4)	0.74539 (12)	0.0856 (6)
H10A	0.2687	0.8250	0.7530	0.128*
H10B	0.3542	0.7976	0.6911	0.128*
H10C	0.3660	0.9830	0.7541	0.128*
C11	0.48003 (16)	0.5549 (3)	0.77912 (11)	0.0682 (5)
H11	0.4847	0.5450	0.7236	0.082*
C12	0.54568 (14)	0.4182 (3)	0.83178 (11)	0.0603 (5)
C13	0.66598 (19)	0.1247 (4)	0.83608 (13)	0.0913 (7)
H13A	0.7034	0.1842	0.8847	0.137*
H13B	0.7176	0.0641	0.8038	0.137*
H13C	0.6171	0.0170	0.8503	0.137*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0558 (7)	0.0803 (9)	0.0782 (8)	0.0017 (6)	0.0075 (6)	−0.0156 (7)
O2	0.0708 (8)	0.0769 (9)	0.0602 (8)	0.0030 (6)	0.0030 (6)	−0.0031 (6)
O3	0.1112 (11)	0.0823 (10)	0.0680 (8)	0.0315 (8)	0.0100 (7)	−0.0054 (7)
N1	0.0600 (9)	0.0757 (10)	0.0604 (9)	0.0114 (7)	0.0069 (7)	0.0021 (7)
C1	0.0526 (10)	0.0670 (11)	0.0537 (9)	−0.0002 (8)	0.0050 (7)	0.0037 (8)
C2	0.0572 (11)	0.0703 (12)	0.0701 (11)	−0.0124 (9)	0.0062 (8)	−0.0107 (9)
C3	0.0465 (9)	0.0752 (13)	0.0709 (11)	−0.0097 (8)	0.0067 (8)	−0.0097 (9)
C4	0.0497 (9)	0.0632 (10)	0.0546 (9)	0.0017 (8)	0.0015 (7)	0.0024 (8)
C5	0.0540 (10)	0.0603 (11)	0.0710 (11)	−0.0080 (8)	0.0030 (8)	−0.0018 (9)
C6	0.0481 (10)	0.0686 (12)	0.0698 (11)	−0.0075 (8)	0.0063 (8)	0.0057 (9)
C7	0.0787 (13)	0.0724 (13)	0.0724 (12)	0.0010 (10)	0.0071 (9)	−0.0102 (10)
C8	0.0949 (15)	0.0886 (15)	0.0745 (12)	0.0188 (12)	0.0097 (11)	−0.0090 (11)
C9	0.0589 (10)	0.0621 (11)	0.0613 (10)	−0.0050 (8)	0.0087 (8)	0.0037 (8)
C10	0.0966 (15)	0.0921 (15)	0.0697 (12)	0.0227 (12)	0.0170 (11)	0.0152 (11)
C11	0.0787 (13)	0.0715 (12)	0.0552 (10)	0.0040 (10)	0.0118 (9)	0.0015 (9)
C12	0.0607 (11)	0.0566 (10)	0.0642 (11)	−0.0066 (8)	0.0088 (8)	−0.0060 (9)
C13	0.1021 (16)	0.0811 (15)	0.0877 (15)	0.0275 (12)	−0.0022 (12)	−0.0071 (12)

Geometric parameters (Å, º)

O1—C4	1.371 (2)	C6—H6	0.93
O1—C7	1.420 (2)	C7—C8	1.493 (3)
O2—C12	1.2187 (19)	C7—H7A	0.97
O3—C12	1.357 (2)	C7—H7B	0.97
O3—C13	1.431 (2)	C8—H8A	0.96
N1—C9	1.341 (2)	C8—H8B	0.96
N1—C1	1.435 (2)	C8—H8C	0.96
N1—H1	0.86	C9—C11	1.360 (3)
C1—C6	1.376 (2)	C9—C10	1.503 (3)
C1—C2	1.383 (2)	C10—H10A	0.96
C2—C3	1.377 (3)	C10—H10B	0.96
C2—H2	0.93	C10—H10C	0.96
C3—C4	1.385 (2)	C11—C12	1.420 (3)
C3—H3	0.93	C11—H11	0.93
C4—C5	1.387 (2)	C13—H13A	0.96
C5—C6	1.384 (2)	C13—H13B	0.96
C5—H5	0.93	C13—H13C	0.96
C4—O1—C7	118.48 (14)	H7A—C7—H7B	108.4
C12—O3—C13	117.32 (15)	C7—C8—H8A	109.5
C9—N1—C1	126.37 (15)	C7—C8—H8B	109.5
C9—N1—H1	116.8	H8A—C8—H8B	109.5
C1—N1—H1	116.8	C7—C8—H8C	109.5
C6—C1—C2	118.81 (16)	H8A—C8—H8C	109.5
C6—C1—N1	120.47 (15)	H8B—C8—H8C	109.5
C2—C1—N1	120.63 (16)	N1—C9—C11	122.43 (16)
C3—C2—C1	120.90 (17)	N1—C9—C10	116.80 (16)
C3—C2—H2	119.6	C11—C9—C10	120.76 (16)
C1—C2—H2	119.6	C9—C10—H10A	109.5
C2—C3—C4	119.86 (16)	C9—C10—H10B	109.5
C2—C3—H3	120.1	H10A—C10—H10B	109.5
C4—C3—H3	120.1	C9—C10—H10C	109.5
O1—C4—C3	115.74 (15)	H10A—C10—H10C	109.5
O1—C4—C5	124.43 (16)	H10B—C10—H10C	109.5
C3—C4—C5	119.83 (16)	C9—C11—C12	123.90 (16)
C6—C5—C4	119.30 (17)	C9—C11—H11	118.0
C6—C5—H5	120.4	C12—C11—H11	118.0
C4—C5—H5	120.4	O2—C12—O3	121.13 (16)
C1—C6—C5	121.23 (16)	O2—C12—C11	126.71 (16)
C1—C6—H6	119.4	O3—C12—C11	112.16 (16)
C5—C6—H6	119.4	O3—C13—H13A	109.5
O1—C7—C8	108.47 (16)	O3—C13—H13B	109.5
O1—C7—H7A	110.0	H13A—C13—H13B	109.5
C8—C7—H7A	110.0	O3—C13—H13C	109.5
O1—C7—H7B	110.0	H13A—C13—H13C	109.5
C8—C7—H7B	110.0	H13B—C13—H13C	109.5
C9—N1—C1—C6	−100.4 (2)	N1—C1—C6—C5	−174.42 (15)
C9—N1—C1—C2	83.0 (2)	C4—C5—C6—C1	−0.1 (3)
C6—C1—C2—C3	−1.9 (3)	C4—O1—C7—C8	−178.42 (16)
N1—C1—C2—C3	174.69 (16)	C1—N1—C9—C11	−177.96 (17)
C1—C2—C3—C4	−0.4 (3)	C1—N1—C9—C10	3.2 (3)
C7—O1—C4—C3	165.99 (15)	N1—C9—C11—C12	1.1 (3)
C7—O1—C4—C5	−13.3 (2)	C10—C9—C11—C12	179.97 (18)
C2—C3—C4—O1	−176.87 (16)	C13—O3—C12—O2	7.7 (3)
C2—C3—C4—C5	2.5 (3)	C13—O3—C12—C11	−172.85 (18)
O1—C4—C5—C6	177.09 (16)	C9—C11—C12—O2	−1.7 (3)
C3—C4—C5—C6	−2.2 (2)	C9—C11—C12—O3	178.90 (18)
C2—C1—C6—C5	2.2 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O2	0.86	2.08	2.741 (2)	133
C6—H6···O2^i	0.93	2.57	3.362 (3)	143

Symmetry code: (i) x, y+1, z.