2,2-Di­methyl-5-(N-methyl-N-methoxy­amino­methyl­ene)-1,3-dioxane-4,6-dione

In the title compound, C₉H₁₃NO₅, the N-methoxy group adopts a conformation almost at right angles to the least-squares mean plane through the other two nitro­gen substit­uents, in a direction opposite to that of the axial methyl substituent on the ring of the Meldrum's acid (2,2-di­methyl-1,3-dioxane-4,6-dione) moiety. There is an indication, at the limits of precision, that delocalization of the N-atom lone pair into the Meldrum's acid ring may be favoured in the direction of one of the two carbonyl groups. The structure is otherwise very similar to that of previously reported 2,2-di­methyl-5-(N,N-di­methyl­amino­methyl­ene)-1,3-dioxane-4,6-dione [Blake et al. (1991). J. Chem. Soc. Perkin Trans. 2, pp. 2003-2010].

Key indicators

• Single-crystal X-ray study
• T = 150 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.043
• wR factor = 0.119
• Data-to-parameter ratio = 11.3

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level B:



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           24.97
         From the CIF: _reflns_number_total               1580
         TEST2: Reflns within _diffrn_reflns_theta_max
         Count of symmetry unique reflns         1828
         Completeness (_total/calc)             86.43%
          Alert B: < 90% complete (theta max?)


 0 Alert Level A = Potentially serious problem

 1 Alert Level B = Potential problem

 0 Alert Level C = Please check

---

S1. Comment

The N-methoxy group N8—O10—C11 in the title compound, (1), adopts a conformation almost at right angles to the C7—N8—C9 plane [the dihedral angle is 89.3 (2)°] in a direction opposite to that of the axial methyl substituent C2a on the Meldrum's acid ring (Fig. 1). The dihedral angle between the C4/C5/C6 and the C7/N8/C9 planes is 26.0 (6)°. By comparison with its N,N-dimethyl analogue, (2) (Blake et al., 1991), the methoxy group has comparatively little structural influence on the molecule as a whole. Thus, many of the values of the corresponding bond lengths and valence angles in (1) and (2) (including C5—C7 and C7—N8) lie within one s.u. of one another and most are within three s.u.'s. The sole significant exception appears to be the bond angles around N8. Thus, in (1), C7—N8—C9 is increased to 130.7 (2)° and C7—N8—O10 reduced to 115.1 (2)° from the corresponding values in (2), which are 123.0 (3) and 121.2 (3)°, respectively. There is an indication, at the limit of the precision of our data, that delocalization of the N7 lone pair into the Meldrum's acid ring may be favoured in the direction of C5—C4—O4. Thus C4—C5 [1.437 (4) Å] displays more double-bond character than C5—C6 [1.452 (4) Å] and C4—O4 [1.218 (3) Å] correspondingly displays more single-bond character than C6—O6 [1.208 (3) Å]. Although this feature was not observed in the structure of (2), we have previously made a similar observation in the structure of the vinylogue (3) (Blake et al., 1991). Interestingly, in this case, the preferred delocalization took place towards the other carbonyl group.

S2. Experimental

The title compound was made by treatment of N,O-dimethylhydroxylamine hydrochloride with methoxymethylene Meldrum's acid in acetonitrile solution, in the presence of triethylamine (McNab & Withell, 2000). Crystals were grown from an ethanol solution.

S3. Refinement

All H atoms were located from a ΔF synthesis, but they were included at geometrically calculated positions. From methyl H atoms C—H was fixed at 0.98 Å; for the remaining atom this distance was 0.95 Å, and U_iso(H) = xU_eq(C), with x = 1.5 for methyl H atoms and 1.2 for the other.

Computing details

Data collection: DIF4 (Stoe & Cie, 1992); cell refinement: DIF4; data reduction: REDU4 (Stoe & Cie, 1992); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2001); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2003).

Figures

Fig. 1. The molecular structure and atom-numbering scheme for 2,2-dimethyl-5-(N-methyl-N-methoxyaminomethylene)-1,3-dioxane-4,6-dione. Displacement ellipsoids are drawn at the 30% probability level.

(1)

Crystal data

C9H13NO5	Z = 2
Mr = 215.20	F(000) = 228
Triclinic, P1	Dx = 1.379 Mg m^−3
a = 6.477 (5) Å	Mo Kα radiation, λ = 0.71073 Å
b = 7.769 (5) Å	Cell parameters from 14 reflections
c = 11.675 (12) Å	θ = 5.5–12.3°
α = 98.04 (7)°	µ = 0.11 mm^−1
β = 100.50 (7)°	T = 150 K
γ = 112.71 (5)°	Cube, colourless
V = 518.4 (7) Å^3	0.23 × 0.19 × 0.19 mm

Data collection

Stoe Stadi-4 four-circle diffractometer	Rint = 0.022
Radiation source: fine-focus sealed tube	θmax = 25.0°, θmin = 2.9°
Graphite monochromator	h = −7→6
ω–2θ scans	k = −8→9
2066 measured reflections	l = 0→13
1580 independent reflections	3 standard reflections every 60 min
1259 reflections with I > 2σ(I)	intensity decay: +−12%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.044	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.119	H atoms treated by a mixture of independent and constrained refinement
S = 1.12	w = 1/[σ^2(Fo^2) + (0.0399P)^2 + 0.537P] where P = (Fo^2 + 2Fc^2)/3
1580 reflections	(Δ/σ)max < 0.001
140 parameters	Δρmax = 0.21 e Å^−3
0 restraints	Δρmin = −0.24 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.

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
O1	−0.0150 (3)	1.2135 (2)	0.23415 (15)	0.0270 (4)
C2	−0.0116 (5)	1.1785 (3)	0.3508 (2)	0.0255 (6)
C2A	0.2275 (5)	1.2909 (4)	0.4349 (2)	0.0309 (6)
H2A1	0.2245	1.2676	0.5134	0.046*
H2A2	0.2743	1.4253	0.4389	0.046*
H2A3	0.3355	1.2512	0.4060	0.046*
C2B	−0.1916 (5)	1.2329 (4)	0.3897 (3)	0.0341 (7)
H2B1	−0.1941	1.2158	0.4694	0.051*
H2B2	−0.3410	1.1528	0.3360	0.051*
H2B3	−0.1545	1.3647	0.3886	0.051*
O3	−0.0887 (3)	0.9764 (2)	0.34389 (16)	0.0271 (4)
C4	0.0039 (4)	0.8786 (4)	0.2788 (2)	0.0244 (6)
O4	−0.0448 (3)	0.7140 (2)	0.28763 (17)	0.0328 (5)
C5	0.1327 (4)	0.9775 (3)	0.2019 (2)	0.0227 (6)
C6	0.0990 (4)	1.1398 (3)	0.1683 (2)	0.0240 (6)
O6	0.1558 (3)	1.2128 (2)	0.08764 (16)	0.0315 (5)
C7	0.2555 (4)	0.9123 (3)	0.1341 (2)	0.0236 (6)
H7	0.2831	0.9702	0.0706	0.028*
N8	0.3388 (4)	0.7853 (3)	0.14329 (19)	0.0261 (5)
C9	0.3595 (5)	0.6835 (4)	0.2379 (3)	0.0319 (6)
H9A	0.2318	0.5590	0.2164	0.048*
H9B	0.3580	0.7551	0.3116	0.048*
H9C	0.5023	0.6696	0.2480	0.048*
O10	0.4618 (3)	0.7640 (2)	0.05947 (17)	0.0317 (5)
C11	0.3105 (5)	0.6064 (4)	−0.0407 (2)	0.0294 (6)
H11A	0.3958	0.5915	−0.0976	0.044*
H11B	0.1842	0.6322	−0.0781	0.044*
H11C	0.2510	0.4906	−0.0130	0.044*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0348 (10)	0.0247 (9)	0.0281 (10)	0.0194 (8)	0.0095 (8)	0.0047 (8)
C2	0.0311 (14)	0.0195 (13)	0.0266 (14)	0.0110 (11)	0.0101 (12)	0.0031 (10)
C2A	0.0319 (15)	0.0277 (14)	0.0299 (15)	0.0119 (12)	0.0063 (13)	0.0014 (12)
C2B	0.0347 (16)	0.0338 (15)	0.0361 (16)	0.0176 (13)	0.0133 (13)	0.0007 (12)
O3	0.0323 (10)	0.0213 (9)	0.0303 (10)	0.0110 (8)	0.0154 (8)	0.0049 (7)
C4	0.0276 (13)	0.0222 (13)	0.0237 (13)	0.0118 (11)	0.0055 (11)	0.0040 (10)
O4	0.0404 (11)	0.0202 (10)	0.0414 (11)	0.0120 (8)	0.0177 (9)	0.0112 (8)
C5	0.0274 (13)	0.0170 (12)	0.0236 (13)	0.0105 (11)	0.0052 (11)	0.0029 (10)
C6	0.0266 (13)	0.0179 (12)	0.0256 (14)	0.0098 (11)	0.0045 (11)	0.0005 (10)
O6	0.0471 (12)	0.0258 (10)	0.0299 (10)	0.0192 (9)	0.0163 (9)	0.0124 (8)
C7	0.0267 (13)	0.0169 (12)	0.0252 (13)	0.0071 (11)	0.0073 (11)	0.0038 (10)
N8	0.0320 (12)	0.0223 (11)	0.0288 (12)	0.0143 (10)	0.0132 (10)	0.0047 (9)
C9	0.0355 (15)	0.0278 (14)	0.0382 (16)	0.0175 (12)	0.0107 (13)	0.0114 (12)
O10	0.0313 (10)	0.0287 (10)	0.0390 (11)	0.0150 (8)	0.0176 (9)	0.0021 (8)
C11	0.0352 (15)	0.0269 (14)	0.0300 (15)	0.0178 (12)	0.0096 (12)	0.0034 (11)

Geometric parameters (Å, º)

O1—C6	1.369 (3)	C5—C7	1.394 (3)
O1—C2	1.424 (3)	C5—C6	1.453 (4)
C2—O3	1.437 (3)	C6—O6	1.208 (3)
C2—C2B	1.505 (4)	C7—N8	1.302 (3)
C2—C2A	1.512 (4)	N8—O10	1.400 (3)
O3—C4	1.368 (3)	N8—C9	1.462 (4)
C4—O4	1.218 (3)	O10—C11	1.443 (4)
C4—C5	1.437 (4)
C6—O1—C2	117.3 (2)	C7—C5—C4	126.2 (2)
O1—C2—O3	109.6 (2)	C7—C5—C6	113.1 (2)
O1—C2—C2B	105.6 (2)	C4—C5—C6	119.3 (2)
O3—C2—C2B	106.5 (2)	O6—C6—O1	117.1 (2)
O1—C2—C2A	111.0 (2)	O6—C6—C5	127.1 (2)
O3—C2—C2A	111.0 (2)	O1—C6—C5	115.7 (2)
C2B—C2—C2A	112.8 (2)	N8—C7—C5	132.0 (2)
C4—O3—C2	118.43 (19)	C7—N8—O10	115.1 (2)
O4—C4—O3	115.9 (2)	C7—N8—C9	130.6 (2)
O4—C4—C5	127.8 (2)	O10—N8—C9	113.4 (2)
O3—C4—C5	116.1 (2)	N8—O10—C11	109.7 (2)
C6—O1—C2—O3	−52.7 (3)	C2—O1—C6—O6	−158.7 (2)
C6—O1—C2—C2B	−167.1 (2)	C2—O1—C6—C5	22.9 (3)
C6—O1—C2—C2A	70.3 (3)	C7—C5—C6—O6	3.5 (4)
O1—C2—O3—C4	47.6 (3)	C4—C5—C6—O6	−164.0 (3)
C2B—C2—O3—C4	161.4 (2)	C7—C5—C6—O1	−178.3 (2)
C2A—C2—O3—C4	−75.4 (3)	C4—C5—C6—O1	14.2 (3)
C2—O3—C4—O4	171.2 (2)	C4—C5—C7—N8	−20.9 (5)
C2—O3—C4—C5	−13.1 (3)	C6—C5—C7—N8	172.6 (3)
O4—C4—C5—C7	−9.7 (5)	C5—C7—N8—O10	−177.6 (2)
O3—C4—C5—C7	175.2 (2)	C5—C7—N8—C9	−9.2 (5)
O4—C4—C5—C6	156.1 (3)	C7—N8—O10—C11	−95.7 (3)
O3—C4—C5—C6	−19.1 (3)	C9—N8—O10—C11	93.9 (3)