5,8-Dimeth­oxy-3,9-dimethyl-3a,4,9,9a-tetra­hydro-4,9-ep­oxy­naphtho­[2,3-d]isoxazole

Abstract

The title compound, C₁₅H₁₇NO₄, is the exo isomer with a syn arrangement of the O atom in the isoxazole ring to the methyl group of the bicyclic alkene. The dihedral angle between the isoxazole ring and the benzene ring is 7.42 (9)°. In the crystal, weak C—H⋯O hydrogen bonds link mol­ecules, forming a three-dimensional network. The isoxazole O atom is an acceptor for both weak hydrogen bonds.

Related literature  

For 1,3-dipolar cyclo­addition reactions of symmetrical and unsymmetrical bicyclic alkenes, see: Yip et al. (2001 ▶); Mayo et al. (2001 ▶). For a related structure, see: Lough et al. (2014 ▶).

Experimental  

Crystal data  

• C₁₅H₁₇NO₄

• M _r = 275.29

• Monoclinic,

• a = 9.0608 (12) Å

• b = 14.3998 (17) Å

• c = 10.1631 (12) Å

• β = 104.835 (3)°

• V = 1281.8 (3) ų

• Z = 4

• Mo Kα radiation

• μ = 0.10 mm⁻¹

• T = 147 K

• 0.32 × 0.16 × 0.14 mm

Data collection  

• Bruker Kappa APEX DUO CCD diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2012 ▶) T _min = 0.660, T _max = 0.746

• 11844 measured reflections

• 2937 independent reflections

• 2271 reflections with I > 2σ(I)

• R _int = 0.041

Refinement  

• R[F ² > 2σ(F ²)] = 0.039

• wR(F ²) = 0.097

• S = 1.05

• 2937 reflections

• 185 parameters

• H-atom parameters constrained

• Δρ_max = 0.28 e Å⁻³

• Δρ_min = −0.22 e Å⁻³

Data collection: APEX2 (Bruker, 2012 ▶); cell refinement: SAINT (Bruker, 2012 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2009 ▶); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▶).

Supplementary Material

CCDC reference: 995953

Additional supporting information: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1A⋯O2i	1.00	2.35	3.2928 (17)	156
C14—H14C⋯O2ii	0.98	2.59	3.5340 (19)	161

Symmetry codes: (i) ; (ii) .

supplementary crystallographic information

1. Comment

We have previously investigated the 1,3-dipolar cycloaddition reactions of symmetrical and unsymmetrical bicyclic alkenes (Yip et al., 2001; Mayo et al., 2001). When expanding this reaction with C1-substituted oxabenzonorbornadienes, the bicyclic alkene (III) reacts (see Fig. 1) with acetonitrile oxide (II) (generated in situ) in toluene, to give the cycloadducts (IV) and (V) as regioisomers in the ratio of 89:11 respectively (ratio was determined by ¹H NMR). The stereochemistry and regiochemistry of the major product (IV) was determined by this single-crystal X-ray analysis. Although different stereoisomers (exo and endo) could be formed, only the exo stereoisomer was formed with a mixture of the corresponding regioisomers. The major product (IV) obtained was found to be the product with the oxygen of the nitrile oxide syn to the C1-methyl group of the bicyclic alkene.

The molecular structure of the title compound is shown in Fig. 2. The dihedral angle between the isoxazole ring (C4/C5/C6/O2/N1 with an r.m.s. deviation 0.0125 Å) and the benzene ring (C8–C13) is 7.42 (9)°. In the crystal, weak C—H···O hydrogen bonds link molecules forming a three-dimensional network (Fig. 3). The isoxazole O atom is an acceptor for both weak hydrogen bonds. We have prepared by a similar method and carried out the structure determination of a related cycloadduct (Lough et al., 2014)

2. Experimental

A solution of nitroethane (I) (130.0 mg, 1.733 mmol) in toluene (2 ml) was added to a flame-dried flask containing bicyclic alkene (II) (140 mg, 0.642 mmol), (BOC)₂O (233.7 mg, 1.07 mmol), DMAP (9.4 mg, 0.077 mmol) and toluene (6 ml) via a cannula over 10 minutes. The reaction mixture was stirred at room temperature for 18 h. The solvent was removed by rotary evaporation, and the crude product was purified by column chromatography (EtOAc:hexanes = 1:9 to 8:2) followed by recrystallization in methanol to give cycloadduct (IV) in 70% yield. Recrystallization of a solution of the title compound in MeOH provided crystals suitable for X-ray diffraction.

3. Refinement

Hydrogen atoms were placed in calculated positions with C—H distances of 0.95–1.00 Å and included in the refinement in a riding-model approximation with U_iso(H) = 1.2U_eq(C) or 1.5U_eq(C_methyl).

Figures

Fig. 1.

The reaction scheme.

Fig. 2.

The molecular structure of the title compound showing 30% probability ellipsoids.

Fig. 3.

Part of the crystal structure with weak hydrogen bonds shown as dashed lines.

Crystal data

C15H17NO4	F(000) = 584
Mr = 275.29	Dx = 1.427 Mg m−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 9.0608 (12) Å	Cell parameters from 2761 reflections
b = 14.3998 (17) Å	θ = 2.5–27.5°
c = 10.1631 (12) Å	µ = 0.10 mm−1
β = 104.835 (3)°	T = 147 K
V = 1281.8 (3) Å3	Needle, colourless
Z = 4	0.32 × 0.16 × 0.14 mm

Data collection

Bruker Kappa APEX DUO CCD diffractometer	2271 reflections with I > 2σ(I)
Radiation source: sealed tube with Bruker Triumph monochromator	Rint = 0.041
φ and ω scans	θmax = 27.5°, θmin = 2.5°
Absorption correction: multi-scan (SADABS; Bruker, 2012)	h = −11→11
Tmin = 0.660, Tmax = 0.746	k = −18→17
11844 measured reflections	l = −11→13
2937 independent reflections

Refinement

Refinement on F2	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.039	H-atom parameters constrained
wR(F2) = 0.097	w = 1/[σ2(Fo2) + (0.0459P)2 + 0.2574P] where P = (Fo2 + 2Fc2)/3
S = 1.05	(Δ/σ)max < 0.001
2937 reflections	Δρmax = 0.28 e Å−3
185 parameters	Δρmin = −0.22 e Å−3

Special details

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.

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

	x	y	z	Uiso*/Ueq
O1	0.50314 (11)	0.25637 (7)	0.36251 (9)	0.0158 (2)
O2	0.59142 (11)	0.27152 (7)	0.66027 (10)	0.0199 (2)
O3	0.27204 (11)	0.49102 (7)	0.15675 (10)	0.0217 (2)
O4	0.89378 (11)	0.43196 (7)	0.37701 (10)	0.0205 (2)
N1	0.44029 (14)	0.24274 (9)	0.65909 (12)	0.0200 (3)
C1	0.39743 (15)	0.33293 (10)	0.34640 (13)	0.0147 (3)
H1A	0.2909	0.3190	0.2927	0.018*
C2	0.63942 (15)	0.30606 (9)	0.43544 (13)	0.0147 (3)
C3	0.77661 (17)	0.24375 (10)	0.46760 (15)	0.0201 (3)
H3A	0.8081	0.2309	0.3841	0.030*
H3B	0.7510	0.1853	0.5060	0.030*
H3C	0.8603	0.2743	0.5338	0.030*
C4	0.58557 (15)	0.34340 (10)	0.55933 (13)	0.0148 (3)
H4A	0.6418	0.4007	0.5992	0.018*
C5	0.41454 (15)	0.36162 (10)	0.49764 (13)	0.0141 (3)
H5A	0.3833	0.4272	0.5086	0.017*
C6	0.34470 (16)	0.29242 (10)	0.57416 (14)	0.0162 (3)
C7	0.17703 (16)	0.27995 (11)	0.55319 (15)	0.0203 (3)
H7A	0.1580	0.2282	0.6092	0.030*
H7B	0.1300	0.2665	0.4570	0.030*
H7C	0.1328	0.3369	0.5795	0.030*
C8	0.47998 (16)	0.40647 (10)	0.28645 (13)	0.0145 (3)
C9	0.42749 (16)	0.48105 (10)	0.20091 (14)	0.0163 (3)
C10	0.53678 (17)	0.53792 (10)	0.16776 (14)	0.0178 (3)
H10A	0.5052	0.5885	0.1070	0.021*
C11	0.69228 (17)	0.52157 (10)	0.22265 (14)	0.0182 (3)
H11A	0.7647	0.5609	0.1976	0.022*
C12	0.74383 (16)	0.44869 (10)	0.31354 (13)	0.0153 (3)
C13	0.63422 (15)	0.39029 (9)	0.34279 (13)	0.0144 (3)
C14	0.21634 (18)	0.57380 (10)	0.08270 (15)	0.0220 (3)
H14A	0.1046	0.5751	0.0622	0.033*
H14B	0.2481	0.5748	−0.0025	0.033*
H14C	0.2581	0.6282	0.1376	0.033*
C15	1.00530 (17)	0.47219 (11)	0.31725 (16)	0.0227 (3)
H15A	1.1070	0.4499	0.3652	0.034*
H15B	1.0019	0.5400	0.3244	0.034*
H15C	0.9835	0.4543	0.2212	0.034*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
O1	0.0159 (5)	0.0130 (5)	0.0180 (5)	−0.0010 (4)	0.0035 (4)	−0.0021 (4)
O2	0.0152 (5)	0.0255 (6)	0.0188 (5)	0.0024 (4)	0.0042 (4)	0.0073 (4)
O3	0.0169 (5)	0.0212 (6)	0.0255 (5)	0.0018 (4)	0.0029 (4)	0.0078 (4)
O4	0.0145 (5)	0.0259 (6)	0.0217 (5)	−0.0024 (4)	0.0057 (4)	0.0032 (4)
N1	0.0188 (6)	0.0216 (7)	0.0211 (6)	−0.0009 (5)	0.0077 (5)	0.0020 (5)
C1	0.0149 (7)	0.0139 (7)	0.0149 (6)	−0.0003 (5)	0.0031 (5)	−0.0003 (5)
C2	0.0140 (7)	0.0143 (7)	0.0161 (6)	−0.0012 (5)	0.0044 (5)	−0.0019 (5)
C3	0.0192 (8)	0.0183 (7)	0.0240 (7)	0.0035 (6)	0.0077 (6)	0.0010 (6)
C4	0.0161 (7)	0.0142 (7)	0.0144 (6)	0.0005 (5)	0.0043 (5)	0.0010 (5)
C5	0.0140 (7)	0.0133 (7)	0.0153 (6)	−0.0003 (5)	0.0044 (5)	−0.0005 (5)
C6	0.0197 (7)	0.0140 (7)	0.0159 (6)	−0.0006 (6)	0.0065 (5)	−0.0013 (5)
C7	0.0180 (8)	0.0220 (8)	0.0228 (7)	−0.0016 (6)	0.0088 (6)	0.0004 (6)
C8	0.0171 (7)	0.0139 (7)	0.0135 (6)	−0.0013 (5)	0.0055 (5)	−0.0025 (5)
C9	0.0171 (7)	0.0177 (7)	0.0140 (6)	0.0011 (6)	0.0035 (5)	−0.0008 (5)
C10	0.0241 (8)	0.0148 (7)	0.0149 (6)	0.0005 (6)	0.0058 (6)	0.0009 (5)
C11	0.0219 (8)	0.0173 (7)	0.0176 (7)	−0.0046 (6)	0.0092 (6)	−0.0027 (6)
C12	0.0151 (7)	0.0175 (7)	0.0144 (6)	−0.0007 (6)	0.0060 (5)	−0.0031 (5)
C13	0.0178 (7)	0.0133 (7)	0.0127 (6)	0.0007 (5)	0.0048 (5)	−0.0026 (5)
C14	0.0232 (8)	0.0204 (8)	0.0209 (7)	0.0060 (6)	0.0029 (6)	0.0048 (6)
C15	0.0165 (7)	0.0279 (8)	0.0256 (8)	−0.0038 (6)	0.0091 (6)	0.0005 (6)

Geometric parameters (Å, º)

O1—C1	1.4420 (16)	C5—C6	1.5001 (19)
O1—C2	1.4550 (16)	C5—H5A	1.0000
O2—N1	1.4278 (16)	C6—C7	1.490 (2)
O2—C4	1.4487 (16)	C7—H7A	0.9800
O3—C9	1.3719 (17)	C7—H7B	0.9800
O3—C14	1.4309 (17)	C7—H7C	0.9800
O4—C12	1.3680 (17)	C8—C9	1.387 (2)
O4—C15	1.4282 (17)	C8—C13	1.3877 (19)
N1—C6	1.2744 (19)	C9—C10	1.391 (2)
C1—C8	1.5118 (18)	C10—C11	1.396 (2)
C1—C5	1.5605 (18)	C10—H10A	0.9500
C1—H1A	1.0000	C11—C12	1.397 (2)
C2—C3	1.4997 (19)	C11—H11A	0.9500
C2—C13	1.5288 (19)	C12—C13	1.3903 (19)
C2—C4	1.5580 (18)	C14—H14A	0.9800
C3—H3A	0.9800	C14—H14B	0.9800
C3—H3B	0.9800	C14—H14C	0.9800
C3—H3C	0.9800	C15—H15A	0.9800
C4—C5	1.5381 (18)	C15—H15B	0.9800
C4—H4A	1.0000	C15—H15C	0.9800
C1—O1—C2	97.72 (10)	C7—C6—C5	123.78 (12)
N1—O2—C4	109.89 (10)	C6—C7—H7A	109.5
C9—O3—C14	116.97 (11)	C6—C7—H7B	109.5
C12—O4—C15	116.97 (11)	H7A—C7—H7B	109.5
C6—N1—O2	109.07 (11)	C6—C7—H7C	109.5
O1—C1—C8	101.45 (10)	H7A—C7—H7C	109.5
O1—C1—C5	101.24 (10)	H7B—C7—H7C	109.5
C8—C1—C5	106.07 (11)	C9—C8—C13	122.42 (13)
O1—C1—H1A	115.4	C9—C8—C1	132.02 (13)
C8—C1—H1A	115.4	C13—C8—C1	105.43 (12)
C5—C1—H1A	115.4	O3—C9—C8	116.40 (12)
O1—C2—C3	111.39 (11)	O3—C9—C10	126.44 (13)
O1—C2—C13	100.84 (10)	C8—C9—C10	117.16 (13)
C3—C2—C13	120.13 (12)	C9—C10—C11	120.80 (13)
O1—C2—C4	100.42 (10)	C9—C10—H10A	119.6
C3—C2—C4	116.36 (11)	C11—C10—H10A	119.6
C13—C2—C4	104.91 (11)	C10—C11—C12	121.55 (13)
C2—C3—H3A	109.5	C10—C11—H11A	119.2
C2—C3—H3B	109.5	C12—C11—H11A	119.2
H3A—C3—H3B	109.5	O4—C12—C13	118.06 (12)
C2—C3—H3C	109.5	O4—C12—C11	124.58 (13)
H3A—C3—H3C	109.5	C13—C12—C11	117.35 (13)
H3B—C3—H3C	109.5	C8—C13—C12	120.62 (13)
O2—C4—C5	105.12 (11)	C8—C13—C2	104.85 (12)
O2—C4—C2	111.31 (11)	C12—C13—C2	134.47 (13)
C5—C4—C2	102.75 (10)	O3—C14—H14A	109.5
O2—C4—H4A	112.3	O3—C14—H14B	109.5
C5—C4—H4A	112.3	H14A—C14—H14B	109.5
C2—C4—H4A	112.3	O3—C14—H14C	109.5
C6—C5—C4	100.96 (11)	H14A—C14—H14C	109.5
C6—C5—C1	112.71 (11)	H14B—C14—H14C	109.5
C4—C5—C1	101.07 (11)	O4—C15—H15A	109.5
C6—C5—H5A	113.6	O4—C15—H15B	109.5
C4—C5—H5A	113.6	H15A—C15—H15B	109.5
C1—C5—H5A	113.6	O4—C15—H15C	109.5
N1—C6—C7	121.36 (13)	H15A—C15—H15C	109.5
N1—C6—C5	114.85 (13)	H15B—C15—H15C	109.5
C4—O2—N1—C6	−3.33 (15)	O1—C1—C8—C13	−32.41 (13)
C2—O1—C1—C8	51.19 (11)	C5—C1—C8—C13	72.97 (13)
C2—O1—C1—C5	−57.97 (11)	C14—O3—C9—C8	172.37 (12)
C1—O1—C2—C3	−179.30 (11)	C14—O3—C9—C10	−8.0 (2)
C1—O1—C2—C13	−50.69 (11)	C13—C8—C9—O3	−177.44 (12)
C1—O1—C2—C4	56.86 (11)	C1—C8—C9—O3	−2.2 (2)
N1—O2—C4—C5	2.76 (13)	C13—C8—C9—C10	2.9 (2)
N1—O2—C4—C2	−107.78 (12)	C1—C8—C9—C10	178.11 (13)
O1—C2—C4—O2	78.42 (12)	O3—C9—C10—C11	178.30 (13)
C3—C2—C4—O2	−41.92 (16)	C8—C9—C10—C11	−2.1 (2)
C13—C2—C4—O2	−177.29 (11)	C9—C10—C11—C12	−0.8 (2)
O1—C2—C4—C5	−33.63 (12)	C15—O4—C12—C13	161.27 (12)
C3—C2—C4—C5	−153.97 (12)	C15—O4—C12—C11	−19.88 (19)
C13—C2—C4—C5	70.66 (12)	C10—C11—C12—O4	−176.08 (12)
O2—C4—C5—C6	−1.30 (13)	C10—C11—C12—C13	2.8 (2)
C2—C4—C5—C6	115.27 (11)	C9—C8—C13—C12	−0.9 (2)
O2—C4—C5—C1	−117.31 (11)	C1—C8—C13—C12	−177.18 (12)
C2—C4—C5—C1	−0.74 (13)	C9—C8—C13—C2	176.63 (12)
O1—C1—C5—C6	−71.58 (13)	C1—C8—C13—C2	0.31 (13)
C8—C1—C5—C6	−177.12 (11)	O4—C12—C13—C8	176.95 (12)
O1—C1—C5—C4	35.38 (12)	C11—C12—C13—C8	−1.98 (19)
C8—C1—C5—C4	−70.15 (13)	O4—C12—C13—C2	0.3 (2)
O2—N1—C6—C7	−178.46 (12)	C11—C12—C13—C2	−178.59 (14)
O2—N1—C6—C5	2.48 (16)	O1—C2—C13—C8	31.49 (13)
C4—C5—C6—N1	−0.72 (15)	C3—C2—C13—C8	154.22 (12)
C1—C5—C6—N1	106.32 (14)	C4—C2—C13—C8	−72.49 (13)
C4—C5—C6—C7	−179.75 (13)	O1—C2—C13—C12	−151.53 (15)
C1—C5—C6—C7	−72.71 (17)	C3—C2—C13—C12	−28.8 (2)
O1—C1—C8—C9	151.77 (14)	C4—C2—C13—C12	104.49 (17)
C5—C1—C8—C9	−102.85 (16)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1A···O2i	1.00	2.35	3.2928 (17)	156
C14—H14C···O2ii	0.98	2.59	3.5340 (19)	161

Symmetry codes: (i) x−1/2, −y+1/2, z−1/2; (ii) −x+1, −y+1, −z+1.