20-Oxa­penta­cyclo­[15.2.1.02,16.03,8.010,15]icosa-2(16),3,5,7,10(15),11,13,18-octaen-9-one

Schollmeyer, D.; Detert, H.

doi:10.1107/S2414314626004992

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 11| Part 5| May 2026| x260499

https://doi.org/10.1107/S2414314626004992

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access

20-Oxapentacyclo[15.2.1.0^2,16.0^3,8.0^10,15]icosa-2(16),3,5,7,10(15),11,13,18-octaen-9-one

Dieter Schollmeyer ^a and Heiner Detert ^a ^*

^aUniversity of Mainz, Department of Chemistry, Duesbergweg 10-14, 55099 Mainz, Germany
^*Correspondence e-mail: [email protected]

Edited by M. Bolte, Goethe-Universität Frankfurt, Germany (Received 6 May 2026; accepted 12 May 2026; online 15 May 2026)

The molecules of the title compound, C₁₉H₁₂O₂, adopt a saddle shape, the o-xylylene fragments are almost planar. The carbonyl group and the ether oxygen atom are located on the same side of the carbon skeleton. The molecules are arranged in strands with alternating directions.

Keywords: crystal structure; tropone; cycloalkyne.

CCDC reference: 2553510

Structure description

Our long-standing interest in the chemistry of strained cycloalkynes of medium ring size (Detert & Meier, 1997 ; Detert et al., 1994 ) and even seven-membered rings (Herges et al., 2005 ; Schollmeyer & Detert, 2023 ) led to the reinvestigation of dibenzocycloheptynone. This compound was trapped in a Diels–Alder reaction with furane (Tochtermann et al., 1964a ). This adduct of dibenzocycloheptynone is a starting material for the synthesis of dibenzofurotropone (Sasaki et al., 1976 ).

The title molecule is shown in Fig. 1. Four molecules fill the monoclinic unit cell. The molecules are arranged in strands parallel to the c axis. Translational symmetry connects the molecules within a strand while a center of inversion connects molecules in parallel strands. As the strands are quite close, the phenyl ring C13–C18 lies over the tropone ring of the next molecule in the vicinal strand. The molecular shape of this virtually mirror symmetrical pentacyclic compound is that of a saddle, the carbonyl group being the pommel, the bicyclic ether group the cantle and the phenyl rings the flaps. The latter subtend a dihedral angle of 28.04 (5)°. The ortho-disubstituted phenyl rings are almost planar: significant deviations from mean plane of C1–C6 are −0.028 (2) Å at C7 and −0.023 (2) Å at C19; deviations from mean plane of C13–C18 are −0.024 (2) Å at C12 and +0.142 (2) Å at C19. The atoms C1, C6, C7, C12, C13, C18 of the tropone moiety are almost coplanar, with a maximum deviation of 0.1317 (9) Å at C16. Atom C19 lies 0.4876 (16) Å above this plane and therefore, the carbonyl group peaks out of the molecular plane. The carbonyl and the ether oxygen atoms are on the same side of the molecule.

Figure 1
View of the title compound. Displacement ellipsoids are drawn at the 50% probability level.

In the extended structure, the molecules are linked by C—H⋯O hydrogen bonds (Fig. 2, Table 1).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C3—H3⋯O20ⁱ	0.95	2.51	3.3886 (17)	153
C10—H10⋯O21ⁱⁱ	0.95	2.48	3.3963 (18)	162
Symmetry codes: (i) ; (ii) .

Figure 2
Part of the packing diagram. View along a-axis direction. Hydrogen atoms removed for clarity.

Synthesis and crystallization

The title compound was prepared by dehydrobromination of 4-bromo[2.3;6.7]-dibenzocycloheptatrienone with potassium tert-butylate in the presence of furane according to Tochtermann (Tochtermann et al., 1964a,b ). The compound was obtained in 67% yield as slightly beige crystals, m.p. = 477–479 K. ¹H-NMR (CDCl₃, 400 MHz;): 6.04 (s, 2 H, OCH, J_CH = 160 Hz). 7.39 (dd, 2 H, J ca 1.6 Hz, olefin), 7.49 (dd, 2 H, J = 8 Hz, J′= 1.5 Hz), 7.56 (ddd, 2 H, J = 7.8 Hz, J′= 1.8 Hz), 7.69 (ddd, 2 H, J = J′= 8 Hz, J′′= 1.3 Hz), 8.10 (dd, 2 H, J = 8 Hz, J′= 1.3 Hz). ¹³C-NMR (CDCl₃, 100 MHz; #x.yz = HMBC cross coupling to H-NMR signal): 85.51, (O—CH, #6.04), 123,43 (CH, #7.49), 129.00 (CH, #7.56), 129.75 (CH, #8.10), 131.69 (Cq), 131.88 (CH, #7.68), 137.97 (Cq), 142.14 (CH, olefin, #7.39), 148.81 (Cq), 194.02 (C=O).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2.

Table 2
Experimental details

Crystal data
Chemical formula	C₁₉H₁₂O₂
M_r	272.29
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	120
a, b, c (Å)	8.5654 (3), 20.7138 (6), 7.4518 (3)
β (°)	105.809 (3)
V (Å³)	1272.10 (8)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.09
Crystal size (mm)	0.55 × 0.35 × 0.17

Data collection
Diffractometer	Stoe IPDS 2T
No. of measured, independent and observed [I > 2σ(I)] reflections	8154, 3014, 2654
R_int	0.020
(sin θ/λ)_max (Å⁻¹)	0.658

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.042, 0.114, 1.02
No. of reflections	3014
No. of parameters	190
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.35, −0.20
Computer programs: X-AREA WinXpose (Stoe & Cie, 2020a ), X-AREA Recipe (Stoe & Cie, 2020b ), X-AREA Integrate (Stoe & Cie, 2020c ), SHELXT2014 (Sheldrick, 2015a ), SHELXL2019/2 (Sheldrick, 2015b ) and PLATON (Spek, 2009 ).

Structural data

CCDC reference: 2553510

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S2414314626004992/bt4199sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314626004992/bt4199Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314626004992/bt4199Isup3.cml

checkCIF report

Computing details top

20-Oxapentacyclo[15.2.1.0^2,16.0^3,8.0^10,15]icosa-2(16),3,5,7,10(15),11,13,18-octaen-9-one top

Crystal data top

C₁₉H₁₂O₂	F(000) = 568
M_r = 272.29	D_x = 1.422 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 8.5654 (3) Å	Cell parameters from 12059 reflections
b = 20.7138 (6) Å	θ = 2.7–28.4°
c = 7.4518 (3) Å	µ = 0.09 mm⁻¹
β = 105.809 (3)°	T = 120 K
V = 1272.10 (8) Å³	Block, colorless
Z = 4	0.55 × 0.35 × 0.17 mm

Data collection top

Stoe IPDS 2T diffractometer	R_int = 0.020
Detector resolution: 6.67 pixels mm^-1	θ_max = 27.9°, θ_min = 2.7°
rotation method, ω scans	h = −11→11
8154 measured reflections	k = −27→27
3014 independent reflections	l = −9→7
2654 reflections with I > 2σ(I)

Refinement top

Refinement on F²	Primary atom site location: dual
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.042	H-atom parameters constrained
wR(F²) = 0.114	w = 1/[σ²(F_o²) + (0.0557P)² + 0.7054P] where P = (F_o² + 2F_c²)/3
S = 1.02	(Δ/σ)_max < 0.001
3014 reflections	Δρ_max = 0.35 e Å⁻³
190 parameters	Δρ_min = −0.20 e Å⁻³
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.

Refinement. Hydrogen atoms were placed at calculated positions and were refined in the riding-model approximation with C_tertiary–H = 1.00 Å or with C–H = 0.95 Å for the remaining H atoms. U_iso(H) were set to 1.2 U_eq(C).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.25685 (15)	0.39001 (6)	0.59801 (17)	0.0202 (3)
C2	0.10665 (16)	0.37416 (7)	0.47387 (19)	0.0251 (3)
H2	0.021235	0.404937	0.449857	0.030*
C3	0.07999 (17)	0.31493 (7)	0.3858 (2)	0.0271 (3)
H3	−0.022313	0.305356	0.301377	0.033*
C4	0.20426 (17)	0.26925 (7)	0.42163 (19)	0.0251 (3)
H4	0.186619	0.228211	0.362647	0.030*
C5	0.35289 (16)	0.28386 (6)	0.54301 (18)	0.0214 (3)
H5	0.436610	0.252354	0.566258	0.026*
C6	0.38439 (15)	0.34424 (6)	0.63376 (17)	0.0185 (3)
C7	0.54171 (15)	0.35550 (6)	0.76243 (17)	0.0183 (3)
C8	0.67373 (16)	0.30275 (6)	0.82756 (19)	0.0222 (3)
H8	0.633420	0.257237	0.818979	0.027*
C9	0.80783 (16)	0.31660 (7)	0.7309 (2)	0.0243 (3)
H9	0.833944	0.291985	0.635415	0.029*
C10	0.87911 (16)	0.37041 (7)	0.80974 (19)	0.0239 (3)
H10	0.967473	0.392565	0.783467	0.029*
C11	0.78726 (15)	0.38891 (6)	0.95271 (18)	0.0209 (3)
H11	0.845070	0.419093	1.053782	0.025*
C12	0.61587 (15)	0.41033 (6)	0.83825 (17)	0.0181 (3)
C13	0.57029 (15)	0.47724 (6)	0.80355 (17)	0.0182 (3)
C14	0.69311 (16)	0.52443 (6)	0.85300 (19)	0.0224 (3)
H14	0.801901	0.511295	0.908102	0.027*
C15	0.65888 (18)	0.58935 (7)	0.8231 (2)	0.0269 (3)
H15	0.743349	0.620381	0.858885	0.032*
C16	0.50090 (19)	0.60910 (7)	0.7409 (2)	0.0281 (3)
H16	0.477393	0.653629	0.717555	0.034*
C17	0.37795 (18)	0.56411 (7)	0.6929 (2)	0.0252 (3)
H17	0.269925	0.578152	0.637738	0.030*
C18	0.40932 (15)	0.49792 (6)	0.72410 (17)	0.0194 (3)
C19	0.26232 (15)	0.45601 (6)	0.68114 (17)	0.0204 (3)
O20	0.74991 (12)	0.32597 (4)	1.01305 (13)	0.0243 (2)
O21	0.13591 (12)	0.47904 (5)	0.70074 (15)	0.0276 (2)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0187 (6)	0.0236 (6)	0.0178 (6)	−0.0009 (5)	0.0045 (5)	0.0008 (5)
C2	0.0182 (6)	0.0329 (7)	0.0226 (6)	0.0004 (5)	0.0029 (5)	−0.0011 (5)
C3	0.0197 (6)	0.0361 (8)	0.0232 (6)	−0.0056 (5)	0.0018 (5)	−0.0034 (5)
C4	0.0266 (7)	0.0264 (7)	0.0219 (6)	−0.0076 (5)	0.0061 (5)	−0.0045 (5)
C5	0.0219 (6)	0.0214 (6)	0.0212 (6)	−0.0018 (5)	0.0064 (5)	0.0001 (5)
C6	0.0188 (6)	0.0200 (6)	0.0166 (5)	−0.0023 (5)	0.0046 (5)	0.0014 (4)
C7	0.0190 (6)	0.0170 (6)	0.0183 (6)	0.0005 (4)	0.0043 (5)	0.0024 (4)
C8	0.0223 (6)	0.0170 (6)	0.0233 (6)	0.0003 (5)	−0.0005 (5)	0.0011 (5)
C9	0.0199 (6)	0.0229 (6)	0.0275 (7)	0.0062 (5)	0.0019 (5)	−0.0017 (5)
C10	0.0169 (6)	0.0247 (6)	0.0285 (7)	0.0028 (5)	0.0032 (5)	−0.0008 (5)
C11	0.0195 (6)	0.0188 (6)	0.0220 (6)	0.0004 (5)	0.0013 (5)	0.0003 (5)
C12	0.0173 (6)	0.0193 (6)	0.0174 (6)	0.0003 (4)	0.0042 (4)	0.0005 (4)
C13	0.0210 (6)	0.0184 (6)	0.0162 (6)	−0.0001 (5)	0.0067 (5)	−0.0008 (4)
C14	0.0236 (6)	0.0207 (6)	0.0238 (6)	−0.0019 (5)	0.0079 (5)	−0.0012 (5)
C15	0.0342 (7)	0.0195 (6)	0.0310 (7)	−0.0053 (5)	0.0158 (6)	−0.0020 (5)
C16	0.0400 (8)	0.0166 (6)	0.0327 (7)	0.0038 (5)	0.0185 (6)	0.0029 (5)
C17	0.0296 (7)	0.0224 (7)	0.0260 (7)	0.0071 (5)	0.0115 (5)	0.0044 (5)
C18	0.0219 (6)	0.0196 (6)	0.0174 (6)	0.0023 (5)	0.0067 (5)	0.0011 (5)
C19	0.0188 (6)	0.0242 (6)	0.0172 (6)	0.0035 (5)	0.0033 (5)	0.0028 (5)
O20	0.0263 (5)	0.0200 (5)	0.0219 (5)	−0.0009 (4)	−0.0013 (4)	0.0030 (4)
O21	0.0206 (5)	0.0312 (5)	0.0308 (5)	0.0054 (4)	0.0068 (4)	−0.0021 (4)

Geometric parameters (Å, º) top

C1—C2	1.4036 (18)	C10—C11	1.5355 (19)
C1—C6	1.4159 (17)	C10—H10	0.9500
C1—C19	1.4963 (18)	C11—O20	1.4432 (15)
C2—C3	1.381 (2)	C11—C12	1.5483 (17)
C2—H2	0.9500	C11—H11	1.0000
C3—C4	1.394 (2)	C12—C13	1.4440 (17)
C3—H3	0.9500	C13—C14	1.4096 (18)
C4—C5	1.3796 (19)	C13—C18	1.4107 (17)
C4—H4	0.9500	C14—C15	1.3814 (19)
C5—C6	1.4123 (18)	C14—H14	0.9500
C5—H5	0.9500	C15—C16	1.386 (2)
C6—C7	1.4441 (17)	C15—H15	0.9500
C7—C12	1.3480 (17)	C16—C17	1.378 (2)
C7—C8	1.5522 (17)	C16—H16	0.9500
C8—O20	1.4409 (16)	C17—C18	1.4042 (18)
C8—C9	1.540 (2)	C17—H17	0.9500
C8—H8	1.0000	C18—C19	1.4906 (18)
C9—C10	1.3285 (19)	C19—O21	1.2278 (16)
C9—H9	0.9500

C2—C1—C6	119.28 (12)	C11—C10—H10	127.6
C2—C1—C19	113.97 (11)	O20—C11—C10	100.93 (10)
C6—C1—C19	126.75 (11)	O20—C11—C12	99.97 (10)
C3—C2—C1	121.62 (13)	C10—C11—C12	106.10 (10)
C3—C2—H2	119.2	O20—C11—H11	115.9
C1—C2—H2	119.2	C10—C11—H11	115.9
C2—C3—C4	119.54 (12)	C12—C11—H11	115.9
C2—C3—H3	120.2	C7—C12—C13	131.30 (12)
C4—C3—H3	120.2	C7—C12—C11	104.91 (11)
C5—C4—C3	119.78 (13)	C13—C12—C11	122.90 (11)
C5—C4—H4	120.1	C14—C13—C18	118.27 (12)
C3—C4—H4	120.1	C14—C13—C12	118.21 (11)
C4—C5—C6	122.01 (13)	C18—C13—C12	123.52 (11)
C4—C5—H5	119.0	C15—C14—C13	121.50 (13)
C6—C5—H5	119.0	C15—C14—H14	119.3
C5—C6—C1	117.76 (11)	C13—C14—H14	119.3
C5—C6—C7	118.88 (11)	C14—C15—C16	119.81 (13)
C1—C6—C7	123.32 (11)	C14—C15—H15	120.1
C12—C7—C6	131.48 (12)	C16—C15—H15	120.1
C12—C7—C8	104.01 (11)	C17—C16—C15	119.99 (13)
C6—C7—C8	124.22 (11)	C17—C16—H16	120.0
O20—C8—C9	100.72 (10)	C15—C16—H16	120.0
O20—C8—C7	99.55 (10)	C16—C17—C18	121.26 (13)
C9—C8—C7	107.17 (10)	C16—C17—H17	119.4
O20—C8—H8	115.7	C18—C17—H17	119.4
C9—C8—H8	115.7	C17—C18—C13	119.14 (12)
C7—C8—H8	115.7	C17—C18—C19	114.88 (12)
C10—C9—C8	105.11 (12)	C13—C18—C19	125.80 (11)
C10—C9—H9	127.4	O21—C19—C18	117.95 (12)
C8—C9—H9	127.4	O21—C19—C1	118.36 (12)
C9—C10—C11	104.82 (12)	C18—C19—C1	123.40 (11)
C9—C10—H10	127.6	C8—O20—C11	94.80 (9)

C6—C1—C2—C3	0.1 (2)	O20—C11—C12—C13	156.23 (11)
C19—C1—C2—C3	−179.44 (12)	C10—C11—C12—C13	−99.23 (13)
C1—C2—C3—C4	0.6 (2)	C7—C12—C13—C14	−158.24 (14)
C2—C3—C4—C5	−0.7 (2)	C11—C12—C13—C14	9.31 (18)
C3—C4—C5—C6	0.0 (2)	C7—C12—C13—C18	22.2 (2)
C4—C5—C6—C1	0.66 (19)	C11—C12—C13—C18	−170.22 (12)
C4—C5—C6—C7	178.52 (12)	C18—C13—C14—C15	−0.79 (19)
C2—C1—C6—C5	−0.71 (18)	C12—C13—C14—C15	179.66 (12)
C19—C1—C6—C5	178.77 (12)	C13—C14—C15—C16	−0.7 (2)
C2—C1—C6—C7	−178.47 (12)	C14—C15—C16—C17	1.4 (2)
C19—C1—C6—C7	1.0 (2)	C15—C16—C17—C18	−0.6 (2)
C5—C6—C7—C12	164.97 (13)	C16—C17—C18—C13	−0.9 (2)
C1—C6—C7—C12	−17.3 (2)	C16—C17—C18—C19	174.62 (12)
C5—C6—C7—C8	−7.79 (18)	C14—C13—C18—C17	1.60 (18)
C1—C6—C7—C8	169.95 (12)	C12—C13—C18—C17	−178.87 (12)
C12—C7—C8—O20	37.21 (12)	C14—C13—C18—C19	−173.43 (12)
C6—C7—C8—O20	−148.37 (11)	C12—C13—C18—C19	6.10 (19)
C12—C7—C8—C9	−67.23 (13)	C17—C18—C19—O21	−30.25 (17)
C6—C7—C8—C9	107.18 (13)	C13—C18—C19—O21	144.96 (13)
O20—C8—C9—C10	−34.00 (13)	C17—C18—C19—C1	143.51 (12)
C7—C8—C9—C10	69.61 (13)	C13—C18—C19—C1	−41.28 (19)
C8—C9—C10—C11	−0.28 (13)	C2—C1—C19—O21	28.98 (17)
C9—C10—C11—O20	34.44 (13)	C6—C1—C19—O21	−150.53 (13)
C9—C10—C11—C12	−69.40 (13)	C2—C1—C19—C18	−144.76 (12)
C6—C7—C12—C13	−6.8 (2)	C6—C1—C19—C18	35.74 (19)
C8—C7—C12—C13	167.04 (13)	C9—C8—O20—C11	53.20 (11)
C6—C7—C12—C11	−175.99 (13)	C7—C8—O20—C11	−56.47 (10)
C8—C7—C12—C11	−2.16 (13)	C10—C11—O20—C8	−53.57 (11)
O20—C11—C12—C7	−33.43 (12)	C12—C11—O20—C8	55.14 (11)
C10—C11—C12—C7	71.12 (12)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3···O20ⁱ	0.95	2.51	3.3886 (17)	153
C10—H10···O21ⁱⁱ	0.95	2.48	3.3963 (18)	162

Symmetry codes: (i) x−1, y, z−1; (ii) x+1, y, z.

References

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