organic compounds
7-(4-Methylphenyl)cyclopenta[a]quinolizine-10-carbaldehyde
aDepartment of Chemistry, Moscow State University, 119992 Moscow, Russian Federation
*Correspondence e-mail: rybakov20021@yandex.ru
In the title compound, C20H15NO, the heterotricycle is essential planar [maximum deviation = 0.0790 (5) Å] and makes a dihedral angle of 50.70 (2)° with the benzene ring. The formyl group is almost coplanar with the tricyclic ring, the C—C—C—O torsion angle being −0.78 (13)°.
Related literature
For background to the Vilsmeier–Haack reaction, see: Laue & Plagens (2005). For a related structure, see: Borisenko et al. (1996).
Experimental
Crystal data
|
Data collection
Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).
Supporting information
https://doi.org/10.1107/S1600536810042467/wm2411sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810042467/wm2411Isup2.hkl
Freshly distilled DMF (1 ml) was added at 263 K to the solution of POCl3 (2.34 mmol, 357 mg) in dry THF (15 ml) forming the Vilsmeier reagent. The solution of 7-(4-methylphenyl)cyclopenta[a]quinolizine 2 (300 mg, 1.17 mmol) in dry THF (10 ml) was added dropwise at 273 K to the Vilsmeier reagent. The mixture was stirred overnight at room temperature, diluted with water, and neutralized by NaOH to pH≈ 8. The resultant precipitate was filtered off and recrystallized from DMF. Yield of 1: 311 mg (93%), m.p. = 527–528 K.
1H NMR (400 MHz; CDCl3; δ, p.p.m.; J, Hz): 2.47 (s, 3H, CH3), 6.80 (d, J = 4.0, 1H), 7.12 (m, 1H), 7.35 (m, 2H, ArH), 7.61 (m, 2H, ArH), 7.64 (s, 1H), 7.77 (d, J = 4.0, 1H), 7.82 (s, 1H), 8.21 (d, J = 7.1, 1H, H4), 9.92 (s, 1H, CHO), 10.53 (d, J = 7.1, 1H, H1).
C-bound H-atoms were placed in calculated positions (C—H 0.93Å; 0.96 Å) and refined as riding, with Uiso(H) = 1.2(1.5)Ueq(C). The initial experimental data were measured for a full sphere, but at the final stage of the ≤ h ≤ +8, -10 ≤ k ≤ +11 and 0 ≤ l ≤ +15.
the 'MERG 2' instruction was used in SHELXL and the DIFABS procedure (Walker & Stuart, 1983) was applied. As a result, we have FVAR = 1, Rint = 0, and the experimental data were reduced to a half-sphere with indices -8Cyclopenta[a]quinolizines are a novel subclass of non-benzenoid heterocycles π-isoelectronic with azulene, so called pseudoazulenes. Some pseudoazulenes show ambident reactivity towards electrophiles, since both α-sites of the cyclopentadiene ring can be substituted. The Vilsmeier–Haack reaction (Laue & Plagens, 2005) (Fig. 1) was one of the simplest tests to estimate the reactivity of cyclopenta[a]quinolizines and the regioselectivity of substitution.
We found that only one product was formed in the reaction. Simple 1H NMR spectra cannot provide an unambiguous proof of the site of substitution. By X-ray analysis we proved that the product is the title compound. From this viewpoint it becomes evident, that the strong shift of the proton H-4 signal (10.53 p.p.m. in 1 against 8.16 in the initial compound 2; Fig. 1) observed in 1H NMR spectra is caused by the peri-effect of the formyl group at C7.
In the title compound 1 (Fig. 2), the bond lengths in the heterocyclic core show slight alternations. The bond length between C7 and C71 of the carbonyl group (1.4351 (8) Å) is much shorter than that in the structure of the simplest aromatic ketone, benzaldehyde (1.477 (3) Å; Borisenko et al., 1996). Since the formyl group is almost co-planar with the tricyclic ring (the torsion angle C8—C7—C71═O71 is -0.78 (13)°), it may indicate strong conjugation of the carbonyl group with the π-excessive cyclopentadiene ring.
For background to the Vilsmeier–Haack reaction, see: Laue & Plagens (2005). For a related structure, see: Borisenko et al. (1996).
Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell
CAD-4 EXPRESS (Enraf–Nonius, 1994); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).C20H15NO | Z = 2 |
Mr = 285.33 | F(000) = 300 |
Triclinic, P1 | Dx = 1.319 Mg m−3 |
Hall symbol: -P 1 | Melting point = 527–528 K |
a = 7.2907 (13) Å | Cu Kα radiation, λ = 1.54184 Å |
b = 8.9627 (14) Å | Cell parameters from 25 reflections |
c = 12.0162 (19) Å | θ = 32.0–34.9° |
α = 88.48 (2)° | µ = 0.64 mm−1 |
β = 81.400 (19)° | T = 295 K |
γ = 67.821 (18)° | Prism, pale yellow |
V = 718.5 (2) Å3 | 0.15 × 0.13 × 0.11 mm |
Enraf–Nonius CAD-4 diffractometer | 2394 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.000 |
Graphite monochromator | θmax = 75.2°, θmin = 3.7° |
non–profiled ω scans | h = −8→9 |
Absorption correction: part of the (Walker & Stuart, 1983) | model (ΔF) k = −10→11 |
Tmin = 0.649, Tmax = 1.000 | l = −11→15 |
3186 measured reflections | 1 standard reflections every 60 min |
2909 independent reflections | intensity decay: 5% |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.024 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.056 | H-atom parameters constrained |
S = 0.96 | w = 1/[σ2(Fo2) + (0.0398P)2] where P = (Fo2 + 2Fc2)/3 |
2909 reflections | (Δ/σ)max = 0.001 |
200 parameters | Δρmax = 0.08 e Å−3 |
61 restraints | Δρmin = −0.10 e Å−3 |
C20H15NO | γ = 67.821 (18)° |
Mr = 285.33 | V = 718.5 (2) Å3 |
Triclinic, P1 | Z = 2 |
a = 7.2907 (13) Å | Cu Kα radiation |
b = 8.9627 (14) Å | µ = 0.64 mm−1 |
c = 12.0162 (19) Å | T = 295 K |
α = 88.48 (2)° | 0.15 × 0.13 × 0.11 mm |
β = 81.400 (19)° |
Enraf–Nonius CAD-4 diffractometer | 2394 reflections with I > 2σ(I) |
Absorption correction: part of the (Walker & Stuart, 1983) | model (ΔF) Rint = 0.000 |
Tmin = 0.649, Tmax = 1.000 | 1 standard reflections every 60 min |
3186 measured reflections | intensity decay: 5% |
2909 independent reflections |
R[F2 > 2σ(F2)] = 0.024 | 61 restraints |
wR(F2) = 0.056 | H-atom parameters constrained |
S = 0.96 | Δρmax = 0.08 e Å−3 |
2909 reflections | Δρmin = −0.10 e Å−3 |
200 parameters |
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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. |
x | y | z | Uiso*/Ueq | ||
N1 | 0.20346 (7) | 0.58547 (5) | 0.01802 (3) | 0.05065 (12) | |
C2 | 0.09520 (9) | 0.71381 (6) | 0.09351 (4) | 0.05806 (16) | |
H2 | 0.0799 | 0.8176 | 0.0716 | 0.070* | |
C3 | 0.01070 (9) | 0.69255 (6) | 0.19859 (4) | 0.05301 (14) | |
C31 | −0.11306 (9) | 0.83714 (6) | 0.27192 (4) | 0.05427 (14) | |
C32 | −0.25884 (9) | 0.96616 (6) | 0.22956 (5) | 0.06118 (16) | |
H32 | −0.2771 | 0.9621 | 0.1549 | 0.073* | |
C33 | −0.37705 (9) | 1.10046 (6) | 0.29708 (5) | 0.06566 (17) | |
H33 | −0.4751 | 1.1849 | 0.2674 | 0.079* | |
C34 | −0.35215 (9) | 1.11184 (7) | 0.40883 (5) | 0.06390 (17) | |
C35 | −0.20805 (10) | 0.98237 (7) | 0.45021 (5) | 0.06909 (18) | |
H35 | −0.1897 | 0.9867 | 0.5248 | 0.083* | |
C36 | −0.08989 (9) | 0.84623 (7) | 0.38403 (4) | 0.06206 (16) | |
H36 | 0.0053 | 0.7606 | 0.4146 | 0.074* | |
C37 | −0.47854 (12) | 1.25985 (8) | 0.48145 (6) | 0.0930 (3) | |
H37A | −0.4965 | 1.2300 | 0.5584 | 0.140* | |
H37B | −0.6068 | 1.3088 | 0.4568 | 0.140* | |
H37C | −0.4128 | 1.3352 | 0.4755 | 0.140* | |
C4 | 0.03745 (9) | 0.53309 (6) | 0.23109 (4) | 0.05122 (14) | |
C5 | −0.03475 (10) | 0.47207 (7) | 0.33034 (5) | 0.06394 (17) | |
H5 | −0.1069 | 0.5315 | 0.3957 | 0.077* | |
C6 | 0.02069 (10) | 0.30912 (7) | 0.31294 (5) | 0.06486 (17) | |
H6 | −0.0075 | 0.2406 | 0.3662 | 0.078* | |
C7 | 0.12585 (9) | 0.25977 (6) | 0.20378 (4) | 0.05555 (15) | |
C71 | 0.17458 (10) | 0.09745 (6) | 0.16468 (5) | 0.06569 (17) | |
H71 | 0.1522 | 0.0286 | 0.2196 | 0.079* | |
O71 | 0.24109 (8) | 0.03569 (5) | 0.07002 (4) | 0.08139 (15) | |
C8 | 0.13764 (8) | 0.40156 (6) | 0.15092 (4) | 0.05205 (14) | |
C9 | 0.23175 (8) | 0.42748 (5) | 0.04415 (4) | 0.04982 (14) | |
C10 | 0.35065 (9) | 0.30555 (6) | −0.03740 (4) | 0.05922 (16) | |
H10 | 0.3721 | 0.1986 | −0.0218 | 0.071* | |
C11 | 0.43433 (9) | 0.34090 (7) | −0.13810 (5) | 0.06062 (16) | |
H11 | 0.5140 | 0.2589 | −0.1903 | 0.073* | |
C12 | 0.39948 (9) | 0.50275 (7) | −0.16278 (5) | 0.06187 (16) | |
H12 | 0.4525 | 0.5283 | −0.2326 | 0.074* | |
C13 | 0.28977 (9) | 0.62042 (7) | −0.08572 (4) | 0.05829 (16) | |
H13 | 0.2711 | 0.7268 | −0.1018 | 0.070* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0615 (3) | 0.03132 (19) | 0.0522 (2) | −0.01155 (18) | −0.00431 (18) | 0.00552 (15) |
C2 | 0.0769 (4) | 0.0302 (2) | 0.0558 (3) | −0.0096 (2) | −0.0049 (2) | 0.00297 (18) |
C3 | 0.0637 (4) | 0.0335 (2) | 0.0543 (3) | −0.0101 (2) | −0.0086 (2) | 0.00249 (18) |
C31 | 0.0664 (4) | 0.0342 (2) | 0.0574 (3) | −0.0167 (2) | −0.0006 (2) | −0.00026 (19) |
C32 | 0.0758 (4) | 0.0377 (2) | 0.0636 (3) | −0.0150 (2) | −0.0081 (3) | 0.0018 (2) |
C33 | 0.0694 (4) | 0.0375 (3) | 0.0808 (3) | −0.0125 (2) | −0.0032 (3) | −0.0015 (2) |
C34 | 0.0673 (4) | 0.0436 (3) | 0.0761 (3) | −0.0236 (3) | 0.0126 (3) | −0.0100 (2) |
C35 | 0.0923 (5) | 0.0540 (3) | 0.0574 (3) | −0.0280 (3) | 0.0017 (3) | −0.0071 (2) |
C36 | 0.0737 (4) | 0.0468 (3) | 0.0595 (3) | −0.0159 (3) | −0.0095 (3) | −0.0008 (2) |
C37 | 0.1015 (6) | 0.0583 (4) | 0.1010 (5) | −0.0230 (4) | 0.0258 (4) | −0.0257 (3) |
C4 | 0.0603 (3) | 0.0355 (2) | 0.0534 (2) | −0.0133 (2) | −0.0083 (2) | 0.00462 (18) |
C5 | 0.0812 (4) | 0.0469 (3) | 0.0529 (3) | −0.0149 (3) | −0.0034 (2) | 0.0080 (2) |
C6 | 0.0814 (4) | 0.0456 (3) | 0.0606 (3) | −0.0183 (3) | −0.0076 (3) | 0.0167 (2) |
C7 | 0.0665 (4) | 0.0346 (2) | 0.0603 (3) | −0.0136 (2) | −0.0102 (2) | 0.01082 (19) |
C71 | 0.0786 (4) | 0.0343 (2) | 0.0753 (3) | −0.0135 (2) | −0.0078 (3) | 0.0114 (2) |
O71 | 0.1109 (4) | 0.0401 (2) | 0.0856 (3) | −0.0254 (2) | 0.0002 (3) | −0.00102 (19) |
C8 | 0.0609 (3) | 0.0335 (2) | 0.0536 (2) | −0.0094 (2) | −0.0077 (2) | 0.00764 (18) |
C9 | 0.0600 (3) | 0.0315 (2) | 0.0536 (2) | −0.0124 (2) | −0.0089 (2) | 0.00413 (18) |
C10 | 0.0743 (4) | 0.0354 (2) | 0.0592 (3) | −0.0124 (2) | −0.0055 (2) | −0.0013 (2) |
C11 | 0.0644 (4) | 0.0505 (3) | 0.0600 (3) | −0.0159 (3) | −0.0026 (2) | −0.0062 (2) |
C12 | 0.0715 (4) | 0.0561 (3) | 0.0520 (3) | −0.0203 (3) | −0.0017 (2) | 0.0028 (2) |
C13 | 0.0727 (4) | 0.0431 (3) | 0.0548 (3) | −0.0195 (2) | −0.0045 (2) | 0.0091 (2) |
N1—C9 | 1.3862 (7) | C37—H37C | 0.9600 |
N1—C2 | 1.3873 (7) | C4—C5 | 1.4119 (8) |
N1—C13 | 1.3934 (7) | C4—C8 | 1.4321 (7) |
C2—C3 | 1.3614 (8) | C5—C6 | 1.3731 (8) |
C2—H2 | 0.9300 | C5—H5 | 0.9300 |
C3—C4 | 1.4198 (7) | C6—C7 | 1.4064 (8) |
C3—C31 | 1.4865 (8) | C6—H6 | 0.9300 |
C31—C32 | 1.3887 (8) | C7—C8 | 1.4315 (8) |
C31—C36 | 1.3909 (8) | C7—C71 | 1.4351 (8) |
C32—C33 | 1.3818 (8) | C71—O71 | 1.2252 (7) |
C32—H32 | 0.9300 | C71—H71 | 0.9300 |
C33—C34 | 1.3930 (9) | C8—C9 | 1.4185 (8) |
C33—H33 | 0.9300 | C9—C10 | 1.4119 (7) |
C34—C35 | 1.3794 (9) | C10—C11 | 1.3570 (8) |
C34—C37 | 1.5061 (8) | C10—H10 | 0.9300 |
C35—C36 | 1.3843 (8) | C11—C12 | 1.4065 (9) |
C35—H35 | 0.9300 | C11—H11 | 0.9300 |
C36—H36 | 0.9300 | C12—C13 | 1.3428 (8) |
C37—H37A | 0.9600 | C12—H12 | 0.9300 |
C37—H37B | 0.9600 | C13—H13 | 0.9300 |
C9—N1—C2 | 122.34 (5) | C5—C4—C3 | 132.01 (5) |
C9—N1—C13 | 120.37 (5) | C5—C4—C8 | 107.93 (5) |
C2—N1—C13 | 117.25 (5) | C3—C4—C8 | 119.75 (5) |
C3—C2—N1 | 122.08 (5) | C6—C5—C4 | 107.68 (5) |
C3—C2—H2 | 119.0 | C6—C5—H5 | 126.2 |
N1—C2—H2 | 119.0 | C4—C5—H5 | 126.2 |
C2—C3—C4 | 118.24 (5) | C5—C6—C7 | 110.93 (6) |
C2—C3—C31 | 118.72 (5) | C5—C6—H6 | 124.5 |
C4—C3—C31 | 122.97 (5) | C7—C6—H6 | 124.5 |
C32—C31—C36 | 118.33 (5) | C6—C7—C8 | 106.27 (5) |
C32—C31—C3 | 120.04 (5) | C6—C7—C71 | 119.19 (6) |
C36—C31—C3 | 121.61 (5) | C8—C7—C71 | 134.02 (5) |
C33—C32—C31 | 120.75 (6) | O71—C71—C7 | 129.90 (6) |
C33—C32—H32 | 119.6 | O71—C71—H71 | 115.1 |
C31—C32—H32 | 119.6 | C7—C71—H71 | 115.1 |
C32—C33—C34 | 121.27 (6) | C9—C8—C7 | 132.70 (5) |
C32—C33—H33 | 119.4 | C9—C8—C4 | 120.05 (5) |
C34—C33—H33 | 119.4 | C7—C8—C4 | 107.18 (5) |
C35—C34—C33 | 117.44 (5) | N1—C9—C10 | 117.65 (5) |
C35—C34—C37 | 121.47 (6) | N1—C9—C8 | 117.11 (5) |
C33—C34—C37 | 121.09 (6) | C10—C9—C8 | 125.24 (5) |
C34—C35—C36 | 122.00 (6) | C11—C10—C9 | 121.49 (5) |
C34—C35—H35 | 119.0 | C11—C10—H10 | 119.3 |
C36—C35—H35 | 119.0 | C9—C10—H10 | 119.3 |
C35—C36—C31 | 120.20 (6) | C10—C11—C12 | 119.40 (5) |
C35—C36—H36 | 119.9 | C10—C11—H11 | 120.3 |
C31—C36—H36 | 119.9 | C12—C11—H11 | 120.3 |
C34—C37—H37A | 109.5 | C13—C12—C11 | 120.09 (5) |
C34—C37—H37B | 109.5 | C13—C12—H12 | 120.0 |
H37A—C37—H37B | 109.5 | C11—C12—H12 | 120.0 |
C34—C37—H37C | 109.5 | C12—C13—N1 | 120.95 (5) |
H37A—C37—H37C | 109.5 | C12—C13—H13 | 119.5 |
H37B—C37—H37C | 109.5 | N1—C13—H13 | 119.5 |
C9—N1—C2—C3 | 0.42 (9) | C5—C6—C7—C71 | −172.26 (6) |
C13—N1—C2—C3 | −177.64 (5) | C6—C7—C71—O71 | 169.69 (7) |
N1—C2—C3—C4 | 0.70 (9) | C8—C7—C71—O71 | −0.78 (13) |
N1—C2—C3—C31 | −176.42 (5) | C6—C7—C8—C9 | 176.75 (6) |
C2—C3—C31—C32 | 47.59 (9) | C71—C7—C8—C9 | −11.90 (12) |
C4—C3—C31—C32 | −129.39 (7) | C6—C7—C8—C4 | −0.13 (7) |
C2—C3—C31—C36 | −133.71 (7) | C71—C7—C8—C4 | 171.22 (7) |
C4—C3—C31—C36 | 49.31 (9) | C5—C4—C8—C9 | −177.74 (5) |
C36—C31—C32—C33 | 0.33 (10) | C3—C4—C8—C9 | 7.92 (9) |
C3—C31—C32—C33 | 179.07 (5) | C5—C4—C8—C7 | −0.38 (7) |
C31—C32—C33—C34 | 0.92 (10) | C3—C4—C8—C7 | −174.73 (6) |
C32—C33—C34—C35 | −1.43 (10) | C2—N1—C9—C10 | −177.72 (5) |
C32—C33—C34—C37 | 178.76 (6) | C13—N1—C9—C10 | 0.29 (8) |
C33—C34—C35—C36 | 0.72 (10) | C2—N1—C9—C8 | 2.57 (8) |
C37—C34—C35—C36 | −179.47 (6) | C13—N1—C9—C8 | −179.42 (5) |
C34—C35—C36—C31 | 0.51 (10) | C7—C8—C9—N1 | 176.80 (6) |
C32—C31—C36—C35 | −1.03 (9) | C4—C8—C9—N1 | −6.65 (8) |
C3—C31—C36—C35 | −179.75 (6) | C7—C8—C9—C10 | −2.89 (11) |
C2—C3—C4—C5 | −177.57 (6) | C4—C8—C9—C10 | 173.67 (5) |
C31—C3—C4—C5 | −0.58 (11) | N1—C9—C10—C11 | −0.16 (9) |
C2—C3—C4—C8 | −4.81 (9) | C8—C9—C10—C11 | 179.52 (5) |
C31—C3—C4—C8 | 172.18 (5) | C9—C10—C11—C12 | −1.05 (10) |
C3—C4—C5—C6 | 174.15 (7) | C10—C11—C12—C13 | 2.19 (10) |
C8—C4—C5—C6 | 0.76 (7) | C11—C12—C13—N1 | −2.10 (10) |
C4—C5—C6—C7 | −0.87 (8) | C9—N1—C13—C12 | 0.86 (9) |
C5—C6—C7—C8 | 0.62 (7) | C2—N1—C13—C12 | 178.96 (5) |
Experimental details
Crystal data | |
Chemical formula | C20H15NO |
Mr | 285.33 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 295 |
a, b, c (Å) | 7.2907 (13), 8.9627 (14), 12.0162 (19) |
α, β, γ (°) | 88.48 (2), 81.400 (19), 67.821 (18) |
V (Å3) | 718.5 (2) |
Z | 2 |
Radiation type | Cu Kα |
µ (mm−1) | 0.64 |
Crystal size (mm) | 0.15 × 0.13 × 0.11 |
Data collection | |
Diffractometer | Enraf–Nonius CAD-4 |
Absorption correction | Part of the refinement model (ΔF) (Walker & Stuart, 1983) |
Tmin, Tmax | 0.649, 1.000 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3186, 2909, 2394 |
Rint | 0.000 |
(sin θ/λ)max (Å−1) | 0.627 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.024, 0.056, 0.96 |
No. of reflections | 2909 |
No. of parameters | 200 |
No. of restraints | 61 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.08, −0.10 |
Computer programs: CAD-4 EXPRESS (Enraf–Nonius, 1994), XCAD4 (Harms & Wocadlo, 1995), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997), WinGX (Farrugia, 1999).
Acknowledgements
The authors are indebted to the Russian Foundation for Basic Research for covering the licence fee for use of the Cambridge Structural Database (Allen, 2002).
References
Allen, F. H. (2002). Acta Cryst. B58, 380–388. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Borisenko, K., Bock, C. & Hargittaij, I. (1996). J. Phys. Chem. 100, 18, 7426–7434. Google Scholar
Enraf–Nonius (1994). CAD-4 EXPRESS. Enraf–Nonius, Delft, The Netherlands. Google Scholar
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565. CrossRef IUCr Journals Google Scholar
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838. CrossRef CAS IUCr Journals Google Scholar
Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany. Google Scholar
Laue, T. & Plagens, A. (2005). Named Organic Reactions, 2nd ed. Chichester, England: Wiley & Sons. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Walker, N. & Stuart, D. (1983). Acta Cryst. A39, 158–166. CrossRef CAS Web of Science IUCr Journals Google Scholar
This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Cyclopenta[a]quinolizines are a novel subclass of non-benzenoid heterocycles π-isoelectronic with azulene, so called pseudoazulenes. Some pseudoazulenes show ambident reactivity towards electrophiles, since both α-sites of the cyclopentadiene ring can be substituted. The Vilsmeier–Haack reaction (Laue & Plagens, 2005) (Fig. 1) was one of the simplest tests to estimate the reactivity of cyclopenta[a]quinolizines and the regioselectivity of substitution.
We found that only one product was formed in the reaction. Simple 1H NMR spectra cannot provide an unambiguous proof of the site of substitution. By X-ray analysis we proved that the product is the title compound. From this viewpoint it becomes evident, that the strong shift of the proton H-4 signal (10.53 p.p.m. in 1 against 8.16 in the initial compound 2; Fig. 1) observed in 1H NMR spectra is caused by the peri-effect of the formyl group at C7.
In the title compound 1 (Fig. 2), the bond lengths in the heterocyclic core show slight alternations. The bond length between C7 and C71 of the carbonyl group (1.4351 (8) Å) is much shorter than that in the structure of the simplest aromatic ketone, benzaldehyde (1.477 (3) Å; Borisenko et al., 1996). Since the formyl group is almost co-planar with the tricyclic ring (the torsion angle C8—C7—C71═O71 is -0.78 (13)°), it may indicate strong conjugation of the carbonyl group with the π-excessive cyclopentadiene ring.