3,5-Di­nitro­xytri­cyclo­[2.2.1.0^2,6]­heptane

The mol­ecule of the title compound, C₇H₇N₂O₆, has a mirror plane through three common C atoms of two five-membered rings, which show distorted envelope conformations. The nitroxy group is in a planar configuration.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.046
• wR factor = 0.112
• Data-to-parameter ratio = 6.6

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           25.98
         From the CIF: _reflns_number_total                485
         Count of symmetry unique reflns          487
         Completeness (_total/calc)             99.59%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured         0
         Fraction of Friedel pairs measured     0.000
         Are heavy atom types Z>Si present           no
          Please check that the estimate of the number of Friedel pairs is
          correct. If it is not, please give the correct count in the
          _publ_section_exptl_refinement section of the submitted CIF.

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S1. Comment

A convenient synthetic method for 3,5-disubstituted nortricyclane derivatives is not available in the literature. Most literature syntheses of 3,5-disubstituted nortricyclanes rely on the electrophilic addition of norbornadiene, which give complex reaction mixtures in which normal addition and Wagner–Meerwein rearrangement stereoisomeric product mixtures are formed (Zefirov et al., 1982).

3,5-Dibromonortricyclanes (2) and (3) (see reaction Scheme) constitute valuable precursors for the preparation of functionalized 3,5-disubstituted norbornadienes. We wish to demonstrate the synthetic potential of cyclopropyl bromides in nortricyclane structures for substitution reactions. Silver-induced nucleophilic substitution reactions of (2) and (3) may be prime tools for difficult to access 3,5-dibromonortricyclane derivatives. For this reason, a dibromonortricyclane mixture [(2) and (3)] in dry acetone was treated with two equivalents of AgClO₄ in dry acetone. After reaction, a 3,5-dinitroxynortricylane product, (5), was obtained in 11% yield as a minor isomer. NMR spectra indicate symmetry in the structure. Two symmetrical structures are possible for the dinitroxy structure. Therefore, it was not possible to establish the exact configuration of the nitroxy groups from NMR investigations. The crystal structure determination established the conformation of (5) to be endo,endo, (I).

It is interesting that both substituents in the structure are in the endo direction, in which we expect a strong dipole–dipole and van der Waals interactions as a consequence of the cis orientation of nitroxy groups. As far as we know no similar example of endo,endo substituents of nortricycane is available in the literature (Chizhov et al., 1987).

The values of the bond distances and angles agree with the literature values (Allen et al., 1987). The five-membered ring (C1–C5) adopts a distorted envelope conformations. The torsion angle C1—C2—C3—C4 is 1.8 (3)°. The nitroxy group is in a planar configuration and the N1—O1 distance [1.391 (3) Å] is in agreement with electron delocalization of the nitro group.

S2. Experimental

Recently, we have succeeded in the preparation of 3,5-dibromonortricyclane by the selective bromination of norbornadiene (Tutar et al., 1996). After completion of the reaction shown in the Scheme above, the reaction mixture was subjected to silica-gel chromatography by eluting with hexane–ethyl acetate. Five fractions were obtained, including compound (5) in a yield of 11%. This was dissolved in boiling acetone and n-hexane was added. The clear solution was cooled slowly to room temperature. After about one day, colourless prism-shaped crystals had formed.

S3. Refinement

All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms.

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens,1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. An ORTEP-3 (Farrugia, 1997) drawing of the title compound with the atom-numbering scheme. Displacement ellipsoids for non-H atoms are drawn at the 35% probability level.
	Fig. 2. A view of the crystal packing along the c axis.

(5)

Crystal data

C7H7N2O6	F(000) = 444
Mr = 215.15	Dx = 1.602 Mg m^−3
Orthorhombic, Cmc21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: C 2c -2	Cell parameters from 2626 reflections
a = 13.4146 (9) Å	θ = 3–26°
b = 6.6414 (5) Å	µ = 0.14 mm^−1
c = 10.0118 (6) Å	T = 293 K
V = 891.97 (10) Å^3	Prism, colorless
Z = 4	0.32 × 0.22 × 0.12 mm

Data collection

Siemens SMART CCD area-detector diffractometer	423 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.072
Graphite monochromator	θmax = 26.0°, θmin = 3.0°
Detector resolution: 8.33 pixels mm^-1	h = −12→16
ω scans	k = −8→7
2626 measured reflections	l = −12→11
485 independent reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.046	H-atom parameters constrained
wR(F^2) = 0.112	w = 1/[σ^2(Fo^2) + (0.0641P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.13	(Δ/σ)max < 0.001
485 reflections	Δρmax = 0.22 e Å^−3
74 parameters	Δρmin = −0.26 e Å^−3
1 restraint	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.023 (5)

Special details

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All e.s.d.'s are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles

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 > 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.

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
O1	0.09919 (13)	0.3326 (3)	−0.1242 (2)	0.0395 (8)
O2	0.1928 (2)	0.3300 (5)	−0.2994 (3)	0.0630 (10)
O3	0.2510 (2)	0.1972 (4)	−0.1175 (4)	0.0640 (11)
N1	0.1888 (2)	0.2810 (4)	−0.1851 (3)	0.0428 (10)
C1	0.0892 (2)	0.2661 (4)	0.0132 (3)	0.0344 (10)
C2	0.0559 (2)	0.0535 (5)	0.0289 (4)	0.0392 (11)
C3	0.00000	0.0464 (8)	0.1590 (5)	0.0443 (16)
C4	0.00000	0.2629 (7)	0.2134 (6)	0.0460 (17)
C5	0.00000	0.3707 (7)	0.0772 (5)	0.0363 (14)
H1A	0.14888	0.29156	0.06311	0.0413*
H2A	0.09476	−0.05742	−0.00351	0.0470*
H3A	0.00000	−0.06945	0.21613	0.0533*
H4A	0.05854	0.29235	0.26473	0.0552*	0.500
H5A	0.00000	0.51504	0.07740	0.0436*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0189 (10)	0.0524 (15)	0.0472 (14)	0.0014 (8)	0.0059 (10)	0.0045 (11)
O2	0.0544 (16)	0.084 (2)	0.0507 (17)	0.0037 (14)	0.0209 (13)	0.0039 (16)
O3	0.0330 (14)	0.079 (2)	0.080 (2)	0.0200 (13)	0.0061 (15)	0.006 (2)
N1	0.0275 (14)	0.0430 (17)	0.058 (2)	0.0007 (11)	0.0117 (13)	−0.0039 (14)
C1	0.0207 (14)	0.0418 (18)	0.0407 (19)	0.0025 (12)	−0.0038 (13)	−0.0010 (14)
C2	0.0354 (18)	0.0394 (18)	0.0427 (19)	0.0083 (13)	0.0002 (15)	0.0001 (14)
C3	0.038 (2)	0.055 (3)	0.040 (3)	0.0000	0.0000	0.011 (2)
C4	0.041 (3)	0.054 (3)	0.043 (3)	0.0000	0.0000	−0.008 (2)
C5	0.030 (2)	0.035 (2)	0.044 (3)	0.0000	0.0000	−0.0044 (18)

Geometric parameters (Å, º)

O1—N1	1.391 (3)	C3—C4	1.538 (7)
O1—C1	1.451 (4)	C4—C5	1.540 (8)
O2—N1	1.191 (4)	C1—H1A	0.9588
O3—N1	1.210 (4)	C2—H2A	0.9590
C1—C2	1.489 (4)	C3—H3A	0.9587
C1—C5	1.525 (4)	C4—H4A	0.9587
C2—C3	1.504 (6)	C5—H5A	0.9586
C2—C2^i	1.500 (4)
O1···C4^ii	3.410 (5)	O3···H2A^iv	2.8704
O1···O1^i	2.661 (2)	N1···O3^iv	2.958 (4)
O1···C4^iii	3.410 (5)	C2···O3	3.148 (4)
O1···O3^iv	3.147 (3)	C4···O1^ix	3.410 (5)
O2···O3^iv	3.136 (5)	C4···O1^x	3.410 (5)
O3···N1^v	2.958 (4)	H1A···O3	2.3535
O3···O1^v	3.147 (3)	H1A···H4A	2.3544
O3···O2^v	3.136 (5)	H1A···O2^xi	2.6565
O3···C2	3.148 (4)	H2A···O3^v	2.8704
O1···H3A^vi	2.7167	H3A···O1^xii	2.7167
O1···H3A^vii	2.7167	H3A···O1^xiii	2.7167
O1···H4A^iii	2.7818	H4A···H1A	2.3544
O2···H1A^viii	2.6565	H4A···O1^x	2.7818
O3···H1A	2.3535	H4A···O3^xi	2.8147
O3···H4A^viii	2.8147
N1—O1—C1	114.9 (2)	O1—C1—H1A	111.30
O1—N1—O2	113.1 (3)	C2—C1—H1A	111.26
O1—N1—O3	117.7 (3)	C5—C1—H1A	110.85
O2—N1—O3	129.2 (3)	C1—C2—H2A	121.97
O1—C1—C2	114.6 (3)	C3—C2—H2A	122.69
O1—C1—C5	109.4 (3)	C2^i—C2—H2A	122.93
C2—C1—C5	98.8 (3)	C2—C3—H3A	122.82
C1—C2—C3	105.7 (3)	C4—C3—H3A	122.63
C1—C2—C2^i	107.5 (3)	C2^i—C3—H3A	122.82
C2^i—C2—C3	60.1 (2)	C3—C4—H4A	112.38
C2—C3—C4	106.1 (4)	C3—C4—H4A^i	112.38
C2—C3—C2^i	59.8 (3)	C5—C4—H4A	112.32
C2^i—C3—C4	106.1 (4)	C5—C4—H4A^i	112.32
C3—C4—C5	97.0 (4)	H4A—C4—H4A^i	110.00
C1—C5—C4	99.2 (3)	C1—C5—H5A	117.16
C1—C5—C1^i	103.4 (3)	C4—C5—H5A	117.58
C1^i—C5—C4	99.2 (3)	C1^i—C5—H5A	117.16
C1—O1—N1—O2	176.9 (3)	C2—C1—C5—C1^i	−46.8 (3)
C1—O1—N1—O3	−3.9 (4)	O1—C1—C2—C3	−150.8 (2)
N1—O1—C1—C2	−82.8 (3)	C1—C2—C3—C2^i	101.4 (3)
N1—O1—C1—C5	167.4 (2)	C2^i—C2—C3—C4	−99.6 (3)
O1—C1—C2—C2^i	−87.9 (3)	C1—C2—C2^i—C3	−98.4 (4)
C5—C1—C2—C3	−34.7 (3)	C1—C2—C2^i—C1^i	0.0 (4)
C5—C1—C2—C2^i	28.3 (4)	C1—C2—C3—C4	1.8 (3)
O1—C1—C5—C4	175.1 (2)	C2—C3—C4—C5	31.27 (18)
O1—C1—C5—C1^i	73.3 (3)	C3—C4—C5—C1	−52.7 (2)
C2—C1—C5—C4	55.1 (3)

Symmetry codes: (i) −x, y, z; (ii) −x, −y+1, z−1/2; (iii) x, −y+1, z−1/2; (iv) −x+1/2, y+1/2, z; (v) −x+1/2, y−1/2, z; (vi) −x, −y, z−1/2; (vii) x, −y, z−1/2; (viii) −x+1/2, −y+1/2, z−1/2; (ix) −x, −y+1, z+1/2; (x) x, −y+1, z+1/2; (xi) −x+1/2, −y+1/2, z+1/2; (xii) −x, −y, z+1/2; (xiii) x, −y, z+1/2.