Di­methyl (1-methyl-1,3-benzimidazol-5-yl)­amino­methyl­ene­propane­dioate monohydrate

In the title compound, C₁₄H₁₅N₃O₄·H₂O, there is a strong conjugation push–pull effect across the central double bond, as reflected in the molecular dimensions and the planarity of the en­amino­ne portion of the mol­ecule. The mol­ecule has an intramolecular hydrogen bond between the NH and CO groups in the Z configuration, adopting the chelated form. The two π systems of the mol­ecule (1-methyl­benz­imidazole and en­amino­ne) are deconjugated and tilted with respect to each other by 15.6 (2)°. The solvent water mol­ecule is hydrogen bonded to the N¹ atom of the 1-methyl­benzimidazolyl group.

S1. Comment

Benzimidazole derivatives having carboxylate group(s) bonded to various positions of the heterocyclic ring are known as orally active nonpeptide angiotensin II receptor antagonists with clinical use in the treatment of hypertension and congestive heart failure (Duncia et al., 1992). Some of these compounds have also been found to antagonize the vascular constrictor and platelet aggregating effects of thromboxanes which make them useful in the treatment of a variety of cardiovascular, renal and respiratory diseases (Nicolai et al., 1993). One point of interest in the present structure, (I), was, therefore, the disposition of the functional (pharmacophoric) groups which in turn is determined by the (π) electronic structure of the molecule. Another point of interest stems from the fact that compound (I) chemically belongs to push-pull ethylenes, a class of compounds with an unusually low rotational barrier around the C═C double bond with an absorption in the near-ultraviolet and visible regions due to delocalization of π electrons. Consequently, it is of interest to examine the extent of conjugation in the title molecule by a combined use of theoretical and experimental methods. In this communication, we report on the crystal structure of (I). \sch

An ORTEPII (Johnson, 1976) view of the molecule is shown in Fig.1. A l l bond distances and angles within the 1-methylbenzimidazolyl part of the molecule are normal and close to those found for unsubstituted 1-methylbenzimidazole (Dik-Edixhoven et al., 1973; Hamilton et al., 1979; Rapta et al., 1995). The ring is planar to within the limits of experimental error [r.m.s. deviation 0.009 (3) Å]. As mentioned above, the (π) electronic structure of the 'enaminone' portion of the molecule is of prime interest here. As judged from the pattern of bond lengths (Table 1), there is an extensive π-electron delocalization involving the donor aminic nitrogen and the acceptor methoxycarbonyl groups. The C11═C12 bond length of 1.378 (4) Å is considerably longer than the reported value of 1.314 (6) Å in unpolarized ethylene (van Nes & Vos, 1977). There is a corresponding reduction in the length of donor-ethylenic and acceptor-ethylenic bonds: the N10—C11 distance is 1.302 (4) Å, which is much shorter than a value of 1.425 (3) Å found for a pure C(sp²)-N(sp²) single bond (Adler et al., 1976). On the acceptor side, the C12—C13 and C12—C17 bond distances of 1.442 (4) and 1.450 (4) Å, respectively, are significantly shorter than the value of 1.487 (5) Å reported for a C(sp²)-C(sp²) single bond (Shmueli et al., 1973). These facts indicate that the structure of this molecular fragment cannot be expressed by a single canonical formula; consequently, there is a structural evidence that forms Ia-c contribute to the π electronic structure of the enaminone portion of the molecule.

The high degree of conjugation across the ethylenic bond is also seen in near coplanarity of the ester groups with the plane of the C═C bond (atoms N10, C11, H11, C12, C13, C17): the dihedral angles of the ester groups with the double-bond plane are 1.8 (3) and 14.9 (3)° for C13, O14, O15, C16 and C17, O18, O19, C20, respectively. Although both ester groups are nearly coplanar with the C═C plane, their conformation is different: while the carbonyl bond of the former ester group (Z to the amine nitrogen) is oriented syn to the C═C bond, the conformation of the latter (E to N10) is anti (Fig.1). The reason for the syn conformation of the 'Z' methoxycarbonyl group is most likely formation of an intramolecular H-bond between N10 and O14 [N10—H···O14, N—H 0.86, H···O 1.99, N···O 2.639 (4) Å, N—H···O 132°]. The twist about the ethylenic bond, as measured by the angle between the planes through N10, C11, H11 and C12, C13, C17, is also small [2.9 (6)°]. Thus, the molecule as a whole consists of two planar π systems, which are mutually deconjugated as shown by the C5—N10 bond length [1.418 (4) Å] approximating the C(sp²)-N single bond [1.425 (3) Å; Adler et al., 1976). The angle between the mean planes through the two planar segments is, however, small [15.8 (2)°].

The molecules related by the twofold axes associate in pairs in an antiparallel fashion due to face-to-face stacking interaction acting between the terminal 1-methylimidazole moieties. The overlapping geometry of the molecules in the dimers is in line with the model of π-π interactions presented by Hunter & Saunders (1990). As the only hydrogen-bond donor of the molecule (N10—H) is involved in the intramolecular hydrogen-bond interaction, the dimers are packed by van der Waals forces. The solvent water molecule is held in the crystal due to hydrogen-bond which it forms with the N3 atom of the 1-methylbenzimidazole moiety [OW—H···N3, O—H 0.84, H···N 2.10, O···N 2.935 (4) Å, O—H···N 170°].

S2. Experimental

5-Nitro-1-methylbenzimidazole (10 mmol) in ethanol was hydrogenated at 120 kPa on Raney nickel till 660 ml of hydrogen was consumed. After the catalyst was filtered off, dimethyl methoxymethylenepropanedioate (10 mmol) was added and the mixture was refluxed for 30 min. The mixture was shortly boiled with charcoal, filtered, the most part of solvent was evaporated, the separated product filtered off and washed with cold ethanol. Crystallization from ethanol/water (4:1 v/v) afforded an analytically pure product (m.p. 451–452 K).

S3. Refinement

Although most of the H atoms were seen in a difference Fourier map, all were refined with fixed geometry, riding on their carrier atoms, with U_iso set to 1.2 (1.5 for the methyl H atoms) times U_eq of the parent atom, except for the water H atoms, the coordinates of which were calculated by using the HYDROGEN program (Nardelli, 1999) and kept fixed during the refinement with U_iso equal to 1.2U_eq of the OW atom.

Computing details

Data collection: XSCANS (Siemens, 1991); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. A view of the title molecule showing the labelling of the non-H atoms. Displacement ellipsoids are shown at the 35% probability level and H atoms are drawn as small circles of arbitrary radii.

Dimethyl (1-Methyl-5-benzimidazolyl)aminomethylenepropanedioate Monohydrate

Crystal data

C14H15N3O4.H2O	Dx = 1.389 Mg m^−3 Dm = 1.39 (1) Mg m^−3 Dm measured by flotation in bromoform/c-hexane
Mr = 307.31	Melting point: 452 K
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 20.012 (8) Å	Cell parameters from 25 reflections
b = 8.929 (3) Å	θ = 8–22°
c = 16.473 (5) Å	µ = 0.11 mm^−1
β = 93.34 (4)°	T = 293 K
V = 2939 (2) Å^3	Plate, brown
Z = 8	0.35 × 0.30 × 0.10 mm
F(000) = 1296

Data collection

Siemens P4 diffractometer	Rint = 0.043
Radiation source: fine-focus sealed tube	θmax = 25.0°, θmin = 2.0°
Graphite monochromator	h = 0→23
ω/2θ scans	k = 0→10
2734 measured reflections	l = −19→19
2592 independent reflections	3 standard reflections every 97 reflections
1334 reflections with I > 2σ(I)	intensity decay: 2%

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F^2 > 2σ(F^2)] = 0.061	Calculated w = 1/[σ^2(Fo^2) + (0.1223P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.144	(Δ/σ)max = 0.005
S = 1.01	Δρmax = 0.35 e Å^−3
2592 reflections	Δρmin = −0.28 e Å^−3
199 parameters

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

	x	y	z	Uiso*/Ueq
N1	1.04685 (12)	0.4960 (3)	0.41310 (14)	0.0471 (7)
C1	1.08518 (17)	0.6237 (4)	0.4428 (2)	0.0640 (10)
H1A	1.1281	0.5908	0.4651	0.096*
H1B	1.0617	0.6733	0.4843	0.096*
H1C	1.0912	0.6920	0.3988	0.096*
C2	1.06123 (16)	0.3508 (4)	0.4241 (2)	0.0551 (9)
H2	1.0989	0.3175	0.4546	0.066*
N3	1.01764 (14)	0.2597 (3)	0.38799 (17)	0.0638 (9)
C4	0.91261 (16)	0.3202 (4)	0.30283 (19)	0.0550 (9)
H4	0.8993	0.2217	0.2934	0.066*
C5	0.87588 (14)	0.4386 (4)	0.27075 (17)	0.0465 (8)
C6	0.89457 (15)	0.5853 (4)	0.2865 (2)	0.0537 (9)
H6	0.8683	0.6624	0.2640	0.064*
C7	0.95034 (16)	0.6198 (4)	0.33418 (19)	0.0529 (9)
H7	0.9623	0.7187	0.3455	0.063*
C8	0.98815 (14)	0.5021 (4)	0.36482 (17)	0.0434 (7)
C9	0.97071 (15)	0.3543 (4)	0.35013 (18)	0.0485 (8)
N10	0.81712 (12)	0.4164 (3)	0.21981 (15)	0.0544 (7)
H10	0.7911	0.4924	0.2123	0.065*
C11	0.79843 (15)	0.2928 (4)	0.18316 (18)	0.0473 (8)
H11	0.8253	0.2092	0.1935	0.057*
C12	0.74299 (14)	0.2731 (3)	0.13066 (17)	0.0434 (8)
C13	0.69904 (16)	0.3985 (4)	0.1133 (2)	0.0532 (9)
O14	0.70709 (13)	0.5209 (3)	0.14387 (18)	0.0876 (9)
O15	0.64808 (11)	0.3712 (2)	0.05957 (14)	0.0612 (7)
C16	0.60151 (18)	0.4913 (4)	0.0436 (3)	0.0810 (12)
H16A	0.5775	0.5103	0.0914	0.121*
H16B	0.5705	0.4640	−0.0005	0.121*
H16C	0.6254	0.5799	0.0295	0.121*
C17	0.73233 (15)	0.1281 (4)	0.09241 (19)	0.0482 (8)
O18	0.69557 (11)	0.0978 (3)	0.03484 (14)	0.0623 (7)
O19	0.77068 (11)	0.0210 (3)	0.13010 (14)	0.0638 (7)
C20	0.7627 (2)	−0.1268 (4)	0.0987 (3)	0.0821 (13)
H20A	0.7166	−0.1563	0.1002	0.123*
H20B	0.7902	−0.1946	0.1312	0.123*
H20C	0.7758	−0.1292	0.0436	0.123*
OW	1.0466 (2)	−0.0336 (4)	0.3176 (3)	0.1610 (17)
H1OW	1.0429	0.0541	0.3357	0.190*
H2OW	1.0854	−0.0378	0.2962	0.190*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0422 (15)	0.0535 (18)	0.0444 (14)	−0.0089 (13)	−0.0087 (12)	0.0000 (13)
C1	0.059 (2)	0.063 (2)	0.068 (2)	−0.0182 (18)	−0.0154 (19)	−0.0061 (19)
C2	0.0482 (19)	0.061 (2)	0.054 (2)	−0.0051 (18)	−0.0191 (16)	0.0071 (17)
N3	0.0627 (18)	0.0542 (18)	0.0706 (19)	−0.0080 (15)	−0.0280 (16)	0.0092 (15)
C4	0.058 (2)	0.048 (2)	0.057 (2)	−0.0123 (17)	−0.0147 (18)	−0.0008 (16)
C5	0.0385 (17)	0.057 (2)	0.0426 (18)	−0.0059 (16)	−0.0082 (14)	−0.0013 (16)
C6	0.0441 (18)	0.054 (2)	0.061 (2)	0.0064 (17)	−0.0067 (16)	−0.0097 (17)
C7	0.0497 (19)	0.050 (2)	0.058 (2)	−0.0026 (16)	−0.0051 (17)	−0.0127 (17)
C8	0.0379 (16)	0.054 (2)	0.0381 (16)	−0.0034 (15)	−0.0035 (14)	−0.0055 (15)
C9	0.0462 (18)	0.051 (2)	0.0470 (18)	−0.0044 (16)	−0.0085 (15)	0.0036 (16)
N10	0.0457 (15)	0.0565 (18)	0.0595 (17)	0.0007 (14)	−0.0099 (13)	−0.0069 (15)
C11	0.0463 (18)	0.050 (2)	0.0449 (17)	−0.0009 (16)	−0.0019 (15)	−0.0014 (16)
C12	0.0371 (17)	0.0465 (19)	0.0453 (18)	−0.0010 (14)	−0.0092 (14)	0.0024 (15)
C13	0.0497 (19)	0.053 (2)	0.055 (2)	−0.0030 (17)	−0.0124 (17)	−0.0012 (18)
O14	0.0856 (19)	0.0540 (17)	0.117 (2)	0.0122 (14)	−0.0488 (17)	−0.0221 (16)
O15	0.0509 (13)	0.0552 (15)	0.0740 (15)	0.0101 (11)	−0.0257 (12)	−0.0041 (12)
C16	0.067 (2)	0.069 (3)	0.102 (3)	0.020 (2)	−0.034 (2)	0.000 (2)
C17	0.0392 (17)	0.058 (2)	0.0467 (19)	0.0022 (16)	−0.0069 (16)	−0.0004 (16)
O18	0.0586 (14)	0.0631 (15)	0.0622 (14)	0.0068 (12)	−0.0235 (12)	−0.0135 (12)
O19	0.0643 (15)	0.0536 (15)	0.0707 (15)	0.0104 (12)	−0.0217 (12)	−0.0029 (13)
C20	0.085 (3)	0.054 (3)	0.105 (3)	0.017 (2)	−0.014 (2)	−0.018 (2)
OW	0.197 (4)	0.071 (2)	0.213 (4)	0.017 (3)	−0.002 (4)	0.002 (3)

Geometric parameters (Å, º)

N1—C2	1.338 (4)	C8—C9	1.383 (4)
N1—C8	1.381 (4)	N10—C11	1.302 (4)
N1—C1	1.444 (4)	C11—C12	1.378 (4)
C2—N3	1.310 (4)	C12—C13	1.442 (4)
N3—C9	1.384 (4)	C12—C17	1.450 (4)
C4—C5	1.375 (4)	C13—O14	1.210 (4)
C4—C9	1.395 (4)	C13—O15	1.333 (4)
C5—C6	1.383 (4)	O15—C16	1.435 (4)
C5—N10	1.418 (4)	C17—O18	1.197 (3)
C6—C7	1.362 (4)	C17—O19	1.354 (4)
C7—C8	1.374 (4)	O19—C20	1.423 (4)
C2—N1—C8	106.6 (3)	C8—C9—C4	120.0 (3)
C2—N1—C1	127.9 (3)	N3—C9—C4	129.8 (3)
C8—N1—C1	125.5 (3)	C11—N10—C5	126.8 (3)
N3—C2—N1	114.1 (3)	N10—C11—C12	126.7 (3)
C2—N3—C9	104.0 (3)	C11—C12—C13	119.0 (3)
C5—C4—C9	117.2 (3)	C11—C12—C17	118.6 (3)
C4—C5—C6	121.5 (3)	C13—C12—C17	122.3 (3)
C4—C5—N10	121.8 (3)	O14—C13—O15	121.3 (3)
C6—C5—N10	116.7 (3)	O14—C13—C12	123.6 (3)
C7—C6—C5	121.8 (3)	O15—C13—C12	115.1 (3)
C6—C7—C8	117.0 (3)	C13—O15—C16	116.6 (3)
C7—C8—N1	132.4 (3)	O18—C17—O19	120.6 (3)
C7—C8—C9	122.5 (3)	O18—C17—C12	127.9 (3)
N1—C8—C9	105.1 (3)	O19—C17—C12	111.5 (3)
C8—C9—N3	110.2 (3)	C17—O19—C20	116.1 (3)
C8—N1—C2—N3	−0.2 (4)	C5—C4—C9—C8	1.8 (5)
C1—N1—C2—N3	−178.4 (3)	C5—C4—C9—N3	−178.3 (3)
N1—C2—N3—C9	0.0 (4)	C4—C5—N10—C11	−15.8 (5)
C9—C4—C5—C6	−1.8 (5)	C6—C5—N10—C11	164.1 (3)
C9—C4—C5—N10	178.1 (3)	C5—N10—C11—C12	−176.7 (3)
C4—C5—C6—C7	0.3 (5)	N10—C11—C12—C13	−0.8 (5)
N10—C5—C6—C7	−179.5 (3)	N10—C11—C12—C17	176.9 (3)
C5—C6—C7—C8	1.2 (5)	C11—C12—C13—O14	−1.8 (5)
C6—C7—C8—N1	178.9 (3)	C17—C12—C13—O14	−179.4 (3)
C6—C7—C8—C9	−1.3 (5)	C11—C12—C13—O15	177.6 (3)
C2—N1—C8—C7	−179.8 (3)	C17—C12—C13—O15	−0.1 (5)
C1—N1—C8—C7	−1.6 (5)	O14—C13—O15—C16	−3.5 (5)
C2—N1—C8—C9	0.3 (3)	C12—C13—O15—C16	177.2 (3)
C1—N1—C8—C9	178.6 (3)	C11—C12—C17—O18	−164.4 (3)
C7—C8—C9—N3	179.8 (3)	C13—C12—C17—O18	13.2 (5)
N1—C8—C9—N3	−0.3 (4)	C11—C12—C17—O19	15.4 (4)
C7—C8—C9—C4	−0.2 (5)	C13—C12—C17—O19	−167.0 (3)
N1—C8—C9—C4	179.6 (3)	O18—C17—O19—C20	−1.9 (5)
C2—N3—C9—C8	0.2 (4)	C12—C17—O19—C20	178.3 (3)
C2—N3—C9—C4	−179.7 (4)