organic compounds
1-[(E)-4-(5-Bromo-1H-indol-3-yl)-1-methyl-2,5,6,7-tetrahydro-1H-azepin-2-ylidene]propan-2-one
aThe School of Chemistry, The University of Manchester, Manchester M13 9PL, England, and bDepartment of Chemistry, Faculty of Science, University of Urmia, Urmia 57135, Iran
*Correspondence e-mail: mmbaradarani@yahoo.com
In the title compound, C18H19BrN2O, the seven-membered azepine ring adopts a twist-boat conformation: the bond angles about the azepine N atom are indicative of sp2 The dihedral angle between the plane of the carbon–carbon double bond of the enone unit and the mean plane of the indole ring is 27.8 (1)°. In the crystal, an N—H⋯O hydrogen bond links the molecules into chains along the b axis.
Related literature
For structure intrepretation tools, see: Allen (2002); Allen et al. (1993); Cremer & Pople (1975). For the reaction chemistry of (Z)-3-(1-methylpyrrolidin-2-ylidene)-3H-indole, see: Bishop et al. (1981a,b, 1982a,b); Harris & Joule (1978a,b).
Experimental
Crystal data
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Refinement
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Data collection: SMART (Bruker, 2001); cell SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009); software used to prepare material for publication: SHELXTL and PLATON.
Supporting information
10.1107/S1600536810019975/jj2030sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536810019975/jj2030Isup2.hkl
(Z)-5-Bromo-3-(1-methylpyrrolidin-2-ylidene)-3H-indole (0.5 g, 1.8 mmol) was heated in refluxing pentane-2,4-dione (11 ml) for 4 h (Fig. 1). When excess diketone was removed by distillation under vacuum, a yellow solid was obtained which was partitioned between 2M HCl and ethyl acetate. The basic product was isolated from the aqueous acidic layer by basification with potassium carbonate and extraction with dichloromethane (0.48 g, 78%). The product was recrystallized in n-hexane/ethanol to give yellow crystalline material, mp 459–461 K.
H atoms bonded to C were included in calculated positions using the riding method, with aromatic, methylene and methyl C—H distances of 0.98, 0.99 and 0.95 Å, respectively and U~eq ~values 1.2 and 1.5 times those of the parent atoms; the torsion angles of the methyl H atoms were optimized to give the best fit to the electron density. The H atom bonded to N1 was found by difference Fourier methods and refined isotropically with N–H = 0.78 (2) Å.
Data collection: SMART (Bruker, 2001); cell
SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).C18H19BrN2O | F(000) = 736 |
Mr = 359.26 | Dx = 1.508 Mg m−3 |
Monoclinic, P21/n | Melting point = 459–461 K |
Hall symbol: -P 2yn | Mo Kα radiation, λ = 0.71073 Å |
a = 14.496 (2) Å | Cell parameters from 915 reflections |
b = 6.6677 (10) Å | θ = 2.8–26.4° |
c = 16.372 (3) Å | µ = 2.60 mm−1 |
β = 90.267 (2)° | T = 100 K |
V = 1582.4 (4) Å3 | Block, yellow |
Z = 4 | 0.30 × 0.20 × 0.20 mm |
Bruker APEX CCD area-detector diffractometer | 3239 independent reflections |
Radiation source: fine-focus sealed tube | 3021 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.023 |
Detector resolution: 8.33 pixels mm-1 | θmax = 26.4°, θmin = 1.9° |
ϕ and ω scans | h = −17→18 |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | k = −8→8 |
Tmin = 0.829, Tmax = 1.000 | l = −20→20 |
12098 measured reflections |
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)] = 0.027 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.069 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.25 | w = 1/[σ2(Fo2) + (0.0342P)2 + 0.3299P] where P = (Fo2 + 2Fc2)/3 |
3239 reflections | (Δ/σ)max = 0.031 |
205 parameters | Δρmax = 0.39 e Å−3 |
0 restraints | Δρmin = −0.23 e Å−3 |
C18H19BrN2O | V = 1582.4 (4) Å3 |
Mr = 359.26 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 14.496 (2) Å | µ = 2.60 mm−1 |
b = 6.6677 (10) Å | T = 100 K |
c = 16.372 (3) Å | 0.30 × 0.20 × 0.20 mm |
β = 90.267 (2)° |
Bruker APEX CCD area-detector diffractometer | 3239 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 3021 reflections with I > 2σ(I) |
Tmin = 0.829, Tmax = 1.000 | Rint = 0.023 |
12098 measured reflections |
R[F2 > 2σ(F2)] = 0.027 | 0 restraints |
wR(F2) = 0.069 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.25 | Δρmax = 0.39 e Å−3 |
3239 reflections | Δρmin = −0.23 e Å−3 |
205 parameters |
Experimental. 1H-NMR (CDCl3) δ (ppm) 2.0 (2H, qn, J = 6.6 Hz, azepin-6-yl-H2), 2.18 (3H, s, MeCO overlying 2H, m, azepin-5-yl-H2),), 3.14 (1H, s, MeN), 3.41 (2H, t, J = 6.3 Hz, azepin-7-yl-H2), 5.19 (1H, s, exocyclic =CH), 6.35 (1H, s, azepin-3-yl-H), 7.0 (1H, d, J = 8.7 Hz, ArH), 7.13 (1H, d, J = 8.7 Hz, ArH), 7.23 (1H, s, indol-4-yl-H), 7.93 (1H, s, indol-2-yl-H), 11.12 (1H, bs, NH). 13C-NMR (CDCl3) δ 28.8, 31.1, 31.4, 39.7, 52.2, 94.6, 113.4, 113.6, 119.6, 122.4, 124.2, 126.4, 127.1, 134.5, 141.3, 163.9, 193.4. νmax 2915, 1611, 1506, 1340, 1189, 972, 787. λmax (EtOH) 236, 261, 350 nm. |
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 against ALL reflections. 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. 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. |
x | y | z | Uiso*/Ueq | ||
Br1 | 0.545967 (12) | 1.20143 (3) | 0.175612 (11) | 0.01975 (8) | |
O1 | 0.13649 (9) | 0.9119 (2) | 0.03015 (7) | 0.0188 (3) | |
N1 | 0.35260 (10) | 0.4764 (2) | 0.30389 (9) | 0.0153 (3) | |
N2 | 0.29940 (10) | 0.4751 (2) | −0.09752 (9) | 0.0140 (3) | |
C1 | 0.30698 (11) | 0.4879 (3) | 0.08357 (10) | 0.0130 (3) | |
C2 | 0.28922 (11) | 0.6432 (3) | 0.03283 (10) | 0.0135 (3) | |
H2 | 0.2962 | 0.7749 | 0.0542 | 0.016* | |
C3 | 0.26004 (11) | 0.6240 (3) | −0.05267 (10) | 0.0131 (3) | |
C4 | 0.38380 (12) | 0.3749 (3) | −0.06878 (10) | 0.0161 (4) | |
H4A | 0.4246 | 0.4753 | −0.0425 | 0.019* | |
H4B | 0.4169 | 0.3188 | −0.1163 | 0.019* | |
C5 | 0.36434 (14) | 0.2070 (3) | −0.00819 (11) | 0.0179 (4) | |
H5A | 0.4223 | 0.1688 | 0.0200 | 0.021* | |
H5B | 0.3410 | 0.0879 | −0.0379 | 0.021* | |
C6 | 0.29263 (13) | 0.2741 (3) | 0.05526 (11) | 0.0165 (4) | |
H6A | 0.2301 | 0.2616 | 0.0311 | 0.020* | |
H6B | 0.2960 | 0.1836 | 0.1031 | 0.020* | |
C7 | 0.33667 (11) | 0.5212 (3) | 0.16813 (10) | 0.0122 (3) | |
C8 | 0.38650 (11) | 0.6899 (2) | 0.20169 (10) | 0.0118 (3) | |
C9 | 0.43010 (11) | 0.8588 (3) | 0.16825 (10) | 0.0135 (3) | |
H9 | 0.4274 | 0.8853 | 0.1113 | 0.016* | |
C10 | 0.47689 (12) | 0.9849 (3) | 0.22064 (11) | 0.0151 (3) | |
C11 | 0.47997 (12) | 0.9571 (3) | 0.30543 (11) | 0.0180 (4) | |
H11 | 0.5106 | 1.0521 | 0.3393 | 0.022* | |
C12 | 0.43834 (13) | 0.7910 (3) | 0.33961 (11) | 0.0170 (4) | |
H12 | 0.4396 | 0.7689 | 0.3969 | 0.020* | |
C13 | 0.39445 (11) | 0.6568 (3) | 0.28686 (10) | 0.0138 (3) | |
C14 | 0.31950 (11) | 0.3958 (3) | 0.23342 (10) | 0.0146 (3) | |
H14 | 0.2887 | 0.2703 | 0.2296 | 0.017* | |
C15 | 0.19750 (12) | 0.7566 (3) | −0.08831 (10) | 0.0147 (3) | |
H15 | 0.1897 | 0.7498 | −0.1459 | 0.018* | |
C16 | 0.14431 (11) | 0.9017 (3) | −0.04539 (10) | 0.0143 (3) | |
C17 | 0.09459 (12) | 1.0600 (3) | −0.09551 (11) | 0.0181 (4) | |
H17A | 0.0310 | 1.0732 | −0.0762 | 0.027* | |
H17B | 0.0941 | 1.0201 | −0.1531 | 0.027* | |
H17C | 0.1265 | 1.1887 | −0.0896 | 0.027* | |
C18 | 0.26809 (13) | 0.4286 (3) | −0.18007 (10) | 0.0183 (4) | |
H18A | 0.2007 | 0.4375 | −0.1826 | 0.027* | |
H18B | 0.2875 | 0.2925 | −0.1946 | 0.027* | |
H18C | 0.2950 | 0.5246 | −0.2185 | 0.027* | |
H1N | 0.3516 (15) | 0.431 (3) | 0.3474 (14) | 0.023 (6)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Br1 | 0.02014 (12) | 0.01765 (12) | 0.02146 (12) | −0.00671 (7) | −0.00231 (8) | 0.00178 (7) |
O1 | 0.0215 (6) | 0.0241 (7) | 0.0106 (6) | 0.0039 (5) | −0.0001 (5) | −0.0015 (5) |
N1 | 0.0172 (7) | 0.0186 (8) | 0.0102 (7) | −0.0021 (6) | −0.0003 (6) | 0.0039 (6) |
N2 | 0.0162 (7) | 0.0159 (7) | 0.0099 (7) | 0.0025 (6) | −0.0014 (5) | −0.0004 (6) |
C1 | 0.0106 (8) | 0.0158 (8) | 0.0125 (8) | −0.0015 (6) | 0.0008 (6) | −0.0009 (7) |
C2 | 0.0116 (8) | 0.0157 (8) | 0.0132 (8) | −0.0010 (6) | −0.0004 (6) | −0.0017 (7) |
C3 | 0.0131 (8) | 0.0146 (8) | 0.0116 (8) | −0.0038 (7) | 0.0006 (6) | 0.0005 (7) |
C4 | 0.0178 (9) | 0.0164 (9) | 0.0140 (8) | 0.0028 (7) | 0.0012 (7) | 0.0013 (7) |
C5 | 0.0249 (10) | 0.0130 (9) | 0.0158 (9) | 0.0016 (7) | −0.0007 (8) | −0.0005 (7) |
C6 | 0.0218 (9) | 0.0151 (9) | 0.0126 (8) | −0.0036 (7) | −0.0010 (7) | 0.0013 (7) |
C7 | 0.0097 (8) | 0.0147 (8) | 0.0122 (8) | 0.0019 (6) | 0.0000 (6) | 0.0001 (6) |
C8 | 0.0099 (8) | 0.0143 (8) | 0.0112 (8) | 0.0029 (6) | 0.0002 (6) | −0.0004 (6) |
C9 | 0.0124 (8) | 0.0160 (8) | 0.0121 (8) | 0.0016 (7) | 0.0000 (6) | 0.0000 (7) |
C10 | 0.0127 (8) | 0.0140 (8) | 0.0186 (9) | −0.0002 (6) | −0.0002 (7) | 0.0012 (7) |
C11 | 0.0180 (9) | 0.0200 (9) | 0.0160 (9) | −0.0019 (7) | −0.0037 (7) | −0.0040 (7) |
C12 | 0.0170 (9) | 0.0217 (10) | 0.0124 (8) | 0.0018 (7) | −0.0017 (7) | −0.0007 (7) |
C13 | 0.0109 (8) | 0.0174 (8) | 0.0129 (8) | 0.0011 (7) | −0.0002 (6) | 0.0011 (7) |
C14 | 0.0133 (8) | 0.0160 (9) | 0.0144 (8) | −0.0002 (7) | −0.0009 (6) | 0.0006 (7) |
C15 | 0.0159 (9) | 0.0191 (8) | 0.0092 (8) | −0.0011 (7) | −0.0023 (7) | 0.0006 (7) |
C16 | 0.0123 (8) | 0.0161 (9) | 0.0145 (8) | −0.0028 (7) | −0.0015 (6) | −0.0001 (7) |
C17 | 0.0184 (9) | 0.0200 (9) | 0.0158 (9) | 0.0028 (7) | −0.0012 (7) | 0.0018 (7) |
C18 | 0.0230 (9) | 0.0185 (9) | 0.0134 (8) | −0.0002 (7) | −0.0013 (7) | −0.0038 (7) |
Br1—C10 | 1.9073 (17) | C7—C14 | 1.381 (2) |
O1—C16 | 1.244 (2) | C7—C8 | 1.444 (2) |
N1—C14 | 1.358 (2) | C8—C9 | 1.404 (2) |
N1—C13 | 1.376 (2) | C8—C13 | 1.416 (2) |
N1—H1N | 0.78 (2) | C9—C10 | 1.377 (2) |
N2—C3 | 1.362 (2) | C9—H9 | 0.9500 |
N2—C18 | 1.457 (2) | C10—C11 | 1.401 (2) |
N2—C4 | 1.469 (2) | C11—C12 | 1.381 (3) |
C1—C2 | 1.352 (2) | C11—H11 | 0.9500 |
C1—C7 | 1.465 (2) | C12—C13 | 1.395 (2) |
C1—C6 | 1.513 (2) | C12—H12 | 0.9500 |
C2—C3 | 1.466 (2) | C14—H14 | 0.9500 |
C2—H2 | 0.9500 | C15—C16 | 1.424 (2) |
C3—C15 | 1.393 (2) | C15—H15 | 0.9500 |
C4—C5 | 1.523 (2) | C16—C17 | 1.517 (2) |
C4—H4A | 0.9900 | C17—H17A | 0.9800 |
C4—H4B | 0.9900 | C17—H17B | 0.9800 |
C5—C6 | 1.540 (3) | C17—H17C | 0.9800 |
C5—H5A | 0.9900 | C18—H18A | 0.9800 |
C5—H5B | 0.9900 | C18—H18B | 0.9800 |
C6—H6A | 0.9900 | C18—H18C | 0.9800 |
C6—H6B | 0.9900 | ||
C14—N1—C13 | 109.16 (15) | C13—C8—C7 | 106.97 (15) |
C14—N1—H1N | 128.0 (17) | C10—C9—C8 | 117.91 (15) |
C13—N1—H1N | 122.8 (17) | C10—C9—H9 | 121.0 |
C3—N2—C18 | 121.71 (14) | C8—C9—H9 | 121.0 |
C3—N2—C4 | 120.60 (14) | C9—C10—C11 | 123.34 (16) |
C18—N2—C4 | 117.12 (14) | C9—C10—Br1 | 118.64 (13) |
C2—C1—C7 | 121.26 (15) | C11—C10—Br1 | 117.95 (13) |
C2—C1—C6 | 120.54 (15) | C12—C11—C10 | 119.71 (16) |
C7—C1—C6 | 118.15 (15) | C12—C11—H11 | 120.1 |
C1—C2—C3 | 124.97 (16) | C10—C11—H11 | 120.1 |
C1—C2—H2 | 117.5 | C11—C12—C13 | 117.54 (17) |
C3—C2—H2 | 117.5 | C11—C12—H12 | 121.2 |
N2—C3—C15 | 120.71 (15) | C13—C12—H12 | 121.2 |
N2—C3—C2 | 117.31 (15) | N1—C13—C12 | 129.44 (16) |
C15—C3—C2 | 121.94 (15) | N1—C13—C8 | 107.56 (15) |
N2—C4—C5 | 112.73 (15) | C12—C13—C8 | 123.00 (16) |
N2—C4—H4A | 109.0 | N1—C14—C7 | 110.71 (16) |
C5—C4—H4A | 109.0 | N1—C14—H14 | 124.6 |
N2—C4—H4B | 109.0 | C7—C14—H14 | 124.6 |
C5—C4—H4B | 109.0 | C3—C15—C16 | 125.26 (16) |
H4A—C4—H4B | 107.8 | C3—C15—H15 | 117.4 |
C4—C5—C6 | 110.69 (14) | C16—C15—H15 | 117.4 |
C4—C5—H5A | 109.5 | O1—C16—C15 | 125.42 (16) |
C6—C5—H5A | 109.5 | O1—C16—C17 | 117.02 (15) |
C4—C5—H5B | 109.5 | C15—C16—C17 | 117.55 (15) |
C6—C5—H5B | 109.5 | C16—C17—H17A | 109.5 |
H5A—C5—H5B | 108.1 | C16—C17—H17B | 109.5 |
C1—C6—C5 | 112.85 (15) | H17A—C17—H17B | 109.5 |
C1—C6—H6A | 109.0 | C16—C17—H17C | 109.5 |
C5—C6—H6A | 109.0 | H17A—C17—H17C | 109.5 |
C1—C6—H6B | 109.0 | H17B—C17—H17C | 109.5 |
C5—C6—H6B | 109.0 | N2—C18—H18A | 109.5 |
H6A—C6—H6B | 107.8 | N2—C18—H18B | 109.5 |
C14—C7—C8 | 105.58 (15) | H18A—C18—H18B | 109.5 |
C14—C7—C1 | 125.92 (16) | N2—C18—H18C | 109.5 |
C8—C7—C1 | 128.47 (15) | H18A—C18—H18C | 109.5 |
C9—C8—C13 | 118.31 (15) | H18B—C18—H18C | 109.5 |
C9—C8—C7 | 134.56 (16) | ||
C7—C1—C2—C3 | 179.45 (15) | C13—C8—C9—C10 | −1.1 (2) |
C6—C1—C2—C3 | −3.2 (3) | C7—C8—C9—C10 | −175.93 (18) |
C18—N2—C3—C15 | −9.5 (2) | C8—C9—C10—C11 | −2.6 (3) |
C4—N2—C3—C15 | 161.62 (16) | C8—C9—C10—Br1 | 174.36 (12) |
C18—N2—C3—C2 | 173.07 (15) | C9—C10—C11—C12 | 3.2 (3) |
C4—N2—C3—C2 | −15.8 (2) | Br1—C10—C11—C12 | −173.73 (14) |
C1—C2—C3—N2 | −38.6 (2) | C10—C11—C12—C13 | 0.0 (3) |
C1—C2—C3—C15 | 144.00 (18) | C14—N1—C13—C12 | −179.52 (18) |
C3—N2—C4—C5 | 83.4 (2) | C14—N1—C13—C8 | 0.26 (19) |
C18—N2—C4—C5 | −105.10 (17) | C11—C12—C13—N1 | 176.04 (18) |
N2—C4—C5—C6 | −44.4 (2) | C11—C12—C13—C8 | −3.7 (3) |
C2—C1—C6—C5 | 70.7 (2) | C9—C8—C13—N1 | −175.47 (15) |
C7—C1—C6—C5 | −111.84 (17) | C7—C8—C13—N1 | 0.68 (19) |
C4—C5—C6—C1 | −40.5 (2) | C9—C8—C13—C12 | 4.3 (3) |
C2—C1—C7—C14 | 150.24 (18) | C7—C8—C13—C12 | −179.53 (16) |
C6—C1—C7—C14 | −27.2 (2) | C13—N1—C14—C7 | −1.2 (2) |
C2—C1—C7—C8 | −27.8 (3) | C8—C7—C14—N1 | 1.53 (19) |
C6—C1—C7—C8 | 154.82 (17) | C1—C7—C14—N1 | −176.84 (15) |
C14—C7—C8—C9 | 173.91 (19) | N2—C3—C15—C16 | 172.13 (16) |
C1—C7—C8—C9 | −7.8 (3) | C2—C3—C15—C16 | −10.5 (3) |
C14—C7—C8—C13 | −1.33 (18) | C3—C15—C16—O1 | −10.6 (3) |
C1—C7—C8—C13 | 176.99 (16) | C3—C15—C16—C17 | 168.01 (16) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1N···O1i | 0.78 (2) | 2.02 (2) | 2.7549 (19) | 159 (2) |
Symmetry code: (i) −x+1/2, y−1/2, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C18H19BrN2O |
Mr | 359.26 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 100 |
a, b, c (Å) | 14.496 (2), 6.6677 (10), 16.372 (3) |
β (°) | 90.267 (2) |
V (Å3) | 1582.4 (4) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 2.60 |
Crystal size (mm) | 0.30 × 0.20 × 0.20 |
Data collection | |
Diffractometer | Bruker APEX CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.829, 1.000 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 12098, 3239, 3021 |
Rint | 0.023 |
(sin θ/λ)max (Å−1) | 0.626 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.027, 0.069, 1.25 |
No. of reflections | 3239 |
No. of parameters | 205 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.39, −0.23 |
Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1N···O1i | 0.78 (2) | 2.02 (2) | 2.7549 (19) | 159 (2) |
Symmetry code: (i) −x+1/2, y−1/2, −z+1/2. |
Acknowledgements
The authors are grateful to the University of Urmia for financial support of the preparative aspects of this work. MA thanks the Daana Pharmaceutical Co (Tabriz-Iran) for the infrared spectra.
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Study of the reaction chemistry of (Z)-3-(1-methylpyrrolidin-2-ylidene)-3H-indole has revealed some remarkable properties and transformations. For example, it was shown to be a remarkably strong base, pKa 10.6, for an imine, to be compared with that for 4a-methyl-1,2,3,4-tetrahydro-4a(i)H-carbazole with a pKa of 3.6 (Harris and Joule, 1978a,b). It reacts with pentane-2,4-dione to give ((E)-4-(1H-indol-3-yl)- 2,5,6,7-tetrahydro-1-methyl-1H-azepin-2-ylidene)propan-2-one via an extensive rearrangement (Bishop et al., 1981a,b). In addition, it reacts with diethyl malonate giving 7-(2-aminophenyl)-5-ethoxycarbonyl-2,3-dihydro-4-hydroxy-1-methylindole, involving another extensive and unprecedented rearrangement (Bishop et al., 1982a,b). We detail here the crystal structure of the product ,(I), C18H19BrN2, formed by reacting (Z)-5-bromo-3-(1-methylpyrrolidin-2-ylidene)-3H-indole with pentane-2,4-dione following the procedure for the des-bromo-prototype (Bishop et al., 1981a,b), (Fig. 1), leading to a 5-bromoindol-3-yl-substituted tetrahydroazepine, (I).
The seven-membered azepine ring adopts a twist-boat conformation as shown by the puckering parameters (Cremer & Pople, 1975; Allen et al., 1993) q2= 1.008 (2); q3= 0.176 (2); ϕ2= 298.0 (1); ϕ3 = 34.4 (6) ° (Spek, 2009), Fig.2. Bond distances and angles in (I) are in the normal range (Allen, 2002). The planar 5-bromoindole bicycle is not coplanar with the enone in the seven-membered azepine ring. The dihedral angle between the enone double bond and the mean plane of the indole ring is 27.8 (1) °. The azepine nitrogen is sp2 hybridized, with the sum of the angles around it being 359.4 °, indicating its conjugating interaction with the exocyclic enone, i.e. it is a vinylogous amide nitrogen. The exocyclic double bond has E geometry. A N1—H1···O1 hydrogen bond between the indole ring and the carbonyl group extending from the propan-2-one group links the molecules into chains along the b axis (Fig. 3).