organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2414-3146

tert-Butyl 2,3-di­hydro-1H-cyclo­penta­[b]indole-4-carboxyl­ate

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aDepartment of Biological and Chemical Sciences, University of the West Indies, Cave Hill, Barbados, bDepartment of Chemistry, Dartmouth College, Hanover, NH 03755-3564, USA, and cDepartment of Chemistry, Keene State College, 229 Main Street, Keene, NH 03435-2001, USA
*Correspondence e-mail: jjasinski@keene.edu

Edited by R. J. Butcher, Howard University, USA (Received 1 September 2016; accepted 16 September 2016; online 27 September 2016)

In the title mol­ecule, C16H19NO2, all the non-hydrogen atoms except two of the C atoms of the tert-butyl group lie on a crystallographic mirror plane. No classical hydrogen bonds are observed. The crystal packing is influenced by weak ππ and C—H⋯π inter­actions.

3D view (loading...)
[Scheme 3D1]
Chemical scheme
[Scheme 1]

Structure description

We report herein the crystal structure of the title compound, which confirms the previously assigned structure in which it was envisioned that the coupling of an indole with a protected hydroxyl benzaldehyde appendage would install the required vinyl group found in the target mol­ecules Prenostodione, Scytonemin and Nostodione (Macor et al., 1989[Macor, J. E., Ryan, K. & Newman, M. E. (1989). Tetrahedron Lett. 30, 2509-2512.]; Badenock et al., 2013[Badenock, J. C., Jordan, J. A. & Gribble, G. W. (2013). Tetrahedron Lett. 54, 2759-2762.]). As such, and in preparation for the coupling, commercially available 1,2,3,4-tetra­hydro­cyclo­penta­[b]indole was converted to the N-BOC derivative using a standard protection protocol in 87% yield. All the atoms except C15 (see Fig. 1[link]) lie on a crystallographic mirror plane: the second methyl group outside the mirror plane is symmetry related and generates the third methyl group in the tert-butyl group.

[Figure 1]
Figure 1
The mol­ecular structure of the title compound, showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50% probability level.

In the crystal, the mol­ecules are in parallel layers alternately inverted along the c axis, parallel to the ac plane (Fig2. 2[link] and 3[link]). The crystal packing is influenced by weak ππ [Cg1–Cg1 and Cg1–Cg2; Cg1–Cg1 = 3.8718 (5) Å and Cg1–Cg2 = 3.7142 (4) Å, where Cg1 is the centroid of the N1/C1/C5/C6/C11 eing and Cg2 is the centroid of the C1–C5 ring] stacking inter­actions involving the pyrrole and cyclo­pentyl moieties and C2—H2(A/B)⋯Cg3(π) [C—H⋯π distance = 2.8 (8) Å; symmetry code: −x + 1, y + [{1\over 2}] (H2A) or y − [{1\over 2}] (H2B), −z + 2; where Cg3 is the centroid of the C6–C11 ring] inter­actions involving the benzene ring.

[Figure 2]
Figure 2
The packing of the title compound, viewed along the b axis.
[Figure 3]
Figure 3
Part of the crystal structure of the title compound, showing the planes of mol­ecules arranged in parallel layers alternately inverted along the c axis, parallel to the ac plane.

Synthesis and crystallization

To a stirred solution of 1,2,3,4-tetra­hydro­cyclo­penta­[b]indole (2.48 g, 15.7 mmol, 1.0 equivalent) in freshly distilled THF (75 ml) was added DMAP (0.10 g, 0.79 mmol, 0.05 equivalents) and di-tert-butyl dicarbonate (5.31 g, 24.3 mmol, 1.5 equivalents), and the resulting mixture allowed to stir at room temperature overnight (Grehn & Ragnarsson, 1984[Grehn, L. & Ragnarsson, U. (1984). Angew. Chem. Int. Ed. 96, 296-301.]). The solvent was removed via rotary evaporation and the subsequent brown residue was absorbed directly onto silica and purified using flash column chromatography (9:1 hexa­nes–ethyl acetate). tert-Butyl 2,3-di­hydro-1H-cyclo­penta­[b]indole-4-carboxyl­ate was obtained as a pale-yellow solid (yield 3.53 g, 87%). Crystals suitable for X-ray diffraction were recrystallized from methanol solution (m.p. 389.0–389.4 K). 1H NMR (CDCl3): δ 8.15–8.17 (d, J = 7.5 Hz, 1H), 7.33–7.35 (m, 1H), 7.16–7.23 (m, 2H), 3.04–3.07 (m, 2H), 2.72–2.76 (m, 2H), 2.42–2.49 (m, 2H), 1.63 (s, 9H); 13C NMR (CDCl3): δ 150.1, 144.1, 140.2, 126.9, 124.5, 122.9, 122.6, 118.6, 115.8, 83.0, 29.2, 28.3, 27.5, 24.1; IR ν film) 3315, 3053, 2980, 2860, 1727, 1611,1476, 1453 cm−1; UV λmax (95% EtOH) 204, 230, 272 nm. Analysis calculated for C16H19NO2: C 74.68, H 7.44, N 5.44%; found: C 74.63, H 7.33, N 5.50.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1[link].

Table 1
Experimental details

Crystal data
Chemical formula C16H19NO2
Mr 257.32
Crystal system, space group Orthorhombic, Pnma
Temperature (K) 173
a, b, c (Å) 19.6761 (11), 7.2330 (4), 9.9258 (7)
V3) 1412.61 (15)
Z 4
Radiation type Mo Kα
μ (mm−1) 0.08
Crystal size (mm) 0.38 × 0.26 × 0.15
 
Data collection
Diffractometer Rigaku-Oxford Diffraction
Absorption correction Multi-scan (CrysAlis PRO & CrysAlis RED; Rigaku-Oxford Diffraction, 2012[Rigaku-Oxford Diffraction (2012). CrysAlis PRO and CrysAlis RED. Rigaku Americas Corporation, The Woodlands, Texas, USA.])
Tmin, Tmax 0.970, 0.988
No. of measured, independent and observed [I > 2σ(I)] reflections 12388, 1808, 1486
Rint 0.029
(sin θ/λ)max−1) 0.658
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.056, 0.147, 1.11
No. of reflections 1808
No. of parameters 113
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.16, −0.18
Computer programs: CrysAlis PRO (Rigaku-Oxford Diffraction, 2012[Rigaku-Oxford Diffraction (2012). CrysAlis PRO and CrysAlis RED. Rigaku Americas Corporation, The Woodlands, Texas, USA.]), CrysAlis RED (Rigaku-Oxford Diffraction, 2012[Rigaku-Oxford Diffraction (2012). CrysAlis PRO and CrysAlis RED. Rigaku Americas Corporation, The Woodlands, Texas, USA.]), SHELXL2014 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]), SHELXT (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]) and OLEX2 (Dolomanov et al., 2009[Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339-341.]).

Structural data


Computing details top

Data collection: CrysAlis PRO (Rigaku-Oxford Diffraction, 2012); cell refinement: CrysAlis PRO (Rigaku-Oxford Diffraction, 2012); data reduction: CrysAlis RED (Rigaku-Oxford Diffraction, 2012); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015b); program(s) used to refine structure: SHELXL (Sheldrick, 2015a); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

tert-Butyl 2,3-dihydro-1H-cyclopenta[b]indole-4-carboxylate top
Crystal data top
C16H19NO2Dx = 1.210 Mg m3
Mr = 257.32Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, PnmaCell parameters from 4596 reflections
a = 19.6761 (11) Åθ = 3.5–32.3°
b = 7.2330 (4) ŵ = 0.08 mm1
c = 9.9258 (7) ÅT = 173 K
V = 1412.61 (15) Å3Block, colourless
Z = 40.38 × 0.26 × 0.15 mm
F(000) = 552
Data collection top
Rigaku-Oxford Diffraction
diffractometer
1486 reflections with I > 2σ(I)
Detector resolution: 16.1500 pixels mm-1Rint = 0.029
ω scansθmax = 27.9°, θmin = 3.5°
Absorption correction: multi-scan
(CrysAlis PRO & CrysAlis RED; Rigaku-Oxford Diffraction, 2012)
h = 2524
Tmin = 0.970, Tmax = 0.988k = 98
12388 measured reflectionsl = 1213
1808 independent reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.056H-atom parameters constrained
wR(F2) = 0.147 w = 1/[σ2(Fo2) + (0.0562P)2 + 0.394P]
where P = (Fo2 + 2Fc2)/3
S = 1.11(Δ/σ)max < 0.001
1808 reflectionsΔρmax = 0.16 e Å3
113 parametersΔρmin = 0.18 e Å3
0 restraints
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
O10.32442 (9)0.25001.10343 (19)0.0736 (6)
O20.35771 (8)0.25000.88593 (17)0.0631 (5)
N10.43643 (8)0.25001.04482 (17)0.0438 (4)
C10.49003 (10)0.25000.9521 (2)0.0408 (4)
C20.49512 (11)0.25000.8034 (2)0.0484 (5)
H2A0.47390.36160.76400.058*0.5
H2B0.47390.13840.76400.058*0.5
C30.57309 (12)0.25000.7828 (2)0.0586 (6)
H3A0.58690.13910.73110.070*0.5
H3B0.58690.36090.73110.070*0.5
C40.60802 (11)0.25000.9211 (2)0.0547 (6)
H4A0.63660.13850.93310.066*0.5
H4B0.63660.36150.93310.066*0.5
C50.54989 (10)0.25001.0164 (2)0.0442 (5)
C60.53714 (12)0.25001.1579 (2)0.0490 (5)
C70.57817 (15)0.25001.2717 (3)0.0674 (7)
H70.62630.25001.26320.081*
C80.5485 (2)0.25001.3961 (3)0.0874 (10)
H80.57650.25001.47410.105*
C90.4784 (2)0.25001.4109 (3)0.0863 (10)
H90.45940.25001.49890.104*
C100.43543 (15)0.25001.3003 (2)0.0652 (7)
H100.38740.25001.31040.078*
C110.46572 (12)0.25001.1746 (2)0.0471 (5)
C120.36713 (10)0.25001.0180 (2)0.0513 (5)
C130.28904 (12)0.25000.8262 (3)0.0673 (7)
C140.30593 (17)0.25000.6773 (3)0.0996 (12)
H14A0.26380.25000.62480.149*
H14B0.33250.36060.65540.149*0.5
H14C0.33250.13940.65540.149*0.5
C150.25196 (10)0.0761 (3)0.8664 (2)0.0919 (8)
H15A0.28140.03110.85140.138*
H15B0.21060.06350.81210.138*
H15C0.23970.08300.96200.138*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0494 (9)0.0972 (14)0.0743 (12)0.0000.0089 (8)0.000
O20.0406 (8)0.0872 (12)0.0614 (10)0.0000.0137 (7)0.000
N10.0427 (9)0.0436 (9)0.0450 (9)0.0000.0029 (7)0.000
C10.0421 (10)0.0340 (9)0.0463 (11)0.0000.0026 (8)0.000
C20.0525 (12)0.0462 (11)0.0466 (11)0.0000.0054 (9)0.000
C30.0579 (13)0.0584 (13)0.0596 (14)0.0000.0092 (11)0.000
C40.0433 (11)0.0507 (12)0.0701 (15)0.0000.0006 (10)0.000
C50.0453 (10)0.0363 (9)0.0511 (11)0.0000.0081 (9)0.000
C60.0559 (12)0.0384 (10)0.0526 (12)0.0000.0109 (10)0.000
C70.0740 (17)0.0687 (15)0.0596 (15)0.0000.0255 (13)0.000
C80.111 (3)0.097 (2)0.0548 (16)0.0000.0305 (17)0.000
C90.122 (3)0.095 (2)0.0414 (13)0.0000.0040 (15)0.000
C100.0810 (17)0.0641 (15)0.0506 (13)0.0000.0058 (12)0.000
C110.0584 (13)0.0382 (10)0.0447 (11)0.0000.0059 (9)0.000
C120.0426 (11)0.0509 (12)0.0603 (13)0.0000.0022 (10)0.000
C130.0450 (12)0.0737 (16)0.0832 (18)0.0000.0249 (12)0.000
C140.079 (2)0.140 (3)0.081 (2)0.0000.0380 (17)0.000
C150.0649 (12)0.0779 (14)0.133 (2)0.0129 (10)0.0315 (12)0.0047 (13)
Geometric parameters (Å, º) top
O1—C121.194 (3)C6—C111.415 (3)
O2—C121.324 (3)C7—H70.9500
O2—C131.476 (3)C7—C81.365 (4)
N1—C11.400 (3)C8—H80.9500
N1—C111.411 (3)C8—C91.388 (5)
N1—C121.389 (3)C9—H90.9500
C1—C21.479 (3)C9—C101.385 (4)
C1—C51.340 (3)C10—H100.9500
C2—H2A0.9900C10—C111.383 (3)
C2—H2B0.9900C13—C141.515 (4)
C2—C31.548 (3)C13—C15i1.508 (3)
C3—H3A0.9900C13—C151.508 (3)
C3—H3B0.9900C14—H14A0.9800
C3—C41.536 (3)C14—H14B0.9800
C4—H4A0.9900C14—H14C0.9800
C4—H4B0.9900C15—H15A0.9800
C4—C51.484 (3)C15—H15B0.9800
C5—C61.427 (3)C15—H15C0.9800
C6—C71.388 (3)
C12—O2—C13121.74 (19)C7—C8—H8119.3
C1—N1—C11107.02 (16)C7—C8—C9121.4 (3)
C12—N1—C1127.82 (18)C9—C8—H8119.3
C12—N1—C11125.16 (18)C8—C9—H9119.3
N1—C1—C2135.00 (17)C10—C9—C8121.5 (3)
C5—C1—N1110.42 (18)C10—C9—H9119.3
C5—C1—C2114.58 (19)C9—C10—H10121.5
C1—C2—H2A111.5C11—C10—C9116.9 (3)
C1—C2—H2B111.5C11—C10—H10121.5
C1—C2—C3101.51 (17)N1—C11—C6107.37 (18)
H2A—C2—H2B109.3C10—C11—N1130.4 (2)
C3—C2—H2A111.5C10—C11—C6122.2 (2)
C3—C2—H2B111.5O1—C12—O2127.2 (2)
C2—C3—H3A109.9O1—C12—N1123.7 (2)
C2—C3—H3B109.9O2—C12—N1109.11 (19)
H3A—C3—H3B108.3O2—C13—C14101.0 (2)
C4—C3—C2108.96 (19)O2—C13—C15109.67 (14)
C4—C3—H3A109.9O2—C13—C15i109.67 (14)
C4—C3—H3B109.9C15i—C13—C14111.38 (16)
C3—C4—H4A111.2C15—C13—C14111.38 (16)
C3—C4—H4B111.2C15i—C13—C15113.0 (2)
H4A—C4—H4B109.1C13—C14—H14A109.5
C5—C4—C3103.01 (17)C13—C14—H14B109.5
C5—C4—H4A111.2C13—C14—H14C109.5
C5—C4—H4B111.2H14A—C14—H14B109.5
C1—C5—C4111.95 (19)H14A—C14—H14C109.5
C1—C5—C6108.33 (19)H14B—C14—H14C109.5
C6—C5—C4139.71 (19)C13—C15—H15A109.5
C7—C6—C5134.3 (2)C13—C15—H15B109.5
C7—C6—C11118.8 (2)C13—C15—H15C109.5
C11—C6—C5106.85 (18)H15A—C15—H15B109.5
C6—C7—H7120.4H15A—C15—H15C109.5
C8—C7—C6119.1 (3)H15B—C15—H15C109.5
C8—C7—H7120.4
N1—C1—C2—C3180.000 (1)C6—C7—C8—C90.000 (1)
N1—C1—C5—C4180.000 (1)C7—C6—C11—N1180.000 (1)
N1—C1—C5—C60.000 (1)C7—C6—C11—C100.000 (1)
C1—N1—C11—C60.000 (1)C7—C8—C9—C100.000 (1)
C1—N1—C11—C10180.000 (1)C8—C9—C10—C110.000 (1)
C1—N1—C12—O1180.000 (1)C9—C10—C11—N1180.000 (1)
C1—N1—C12—O20.000 (1)C9—C10—C11—C60.000 (1)
C1—C2—C3—C40.000 (1)C11—N1—C1—C2180.000 (1)
C1—C5—C6—C7180.000 (1)C11—N1—C1—C50.000 (1)
C1—C5—C6—C110.000 (1)C11—N1—C12—O10.000 (1)
C2—C1—C5—C40.000 (1)C11—N1—C12—O2180.000 (1)
C2—C1—C5—C6180.000 (1)C11—C6—C7—C80.000 (1)
C2—C3—C4—C50.000 (1)C12—O2—C13—C14180.000 (1)
C3—C4—C5—C10.000 (1)C12—O2—C13—C15i62.35 (18)
C3—C4—C5—C6180.000 (1)C12—O2—C13—C1562.35 (18)
C4—C5—C6—C70.000 (1)C12—N1—C1—C20.000 (1)
C4—C5—C6—C11180.000 (1)C12—N1—C1—C5180.000 (1)
C5—C1—C2—C30.000 (1)C12—N1—C11—C6180.000 (1)
C5—C6—C7—C8180.000 (1)C12—N1—C11—C100.000 (1)
C5—C6—C11—N10.000 (1)C13—O2—C12—O10.000 (1)
C5—C6—C11—C10180.000 (1)C13—O2—C12—N1180.000 (1)
Symmetry code: (i) x, y+1/2, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C10—H10···O10.952.402.931 (3)115
C15—H15C···O10.982.493.025 (3)114
 

Acknowledgements

JCB wishes to thank the School of Graduate Studies and Research, UWI and the Government of Barbados for the funding of this research. JPJ acknowledges the NSF–MRI program (grant No. CHE-0619278) for funds to purchase the X-ray diffractometer.

References

First citationBadenock, J. C., Jordan, J. A. & Gribble, G. W. (2013). Tetrahedron Lett. 54, 2759–2762.  CrossRef CAS Google Scholar
First citationDolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339–341.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationGrehn, L. & Ragnarsson, U. (1984). Angew. Chem. Int. Ed. 96, 296–301.  CrossRef Google Scholar
First citationMacor, J. E., Ryan, K. & Newman, M. E. (1989). Tetrahedron Lett. 30, 2509–2512.  CrossRef CAS Google Scholar
First citationRigaku-Oxford Diffraction (2012). CrysAlis PRO and CrysAlis RED. Rigaku Americas Corporation, The Woodlands, Texas, USA.  Google Scholar
First citationSheldrick, G. M. (2015a). Acta Cryst. A71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar
First citationSheldrick, G. M. (2015b). Acta Cryst. C71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar

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