4-Diethyl­amino-3,5-diisopropyl­benzalde­hyde

Abstract

The title benzaldehyde, C₁₇H₂₇NO, was prepared via lithia­tion of bromoaniline and reaction with DMF. In the crystal, the molecule adopts a C2-symmetrical conformation; nevertheless, two modes of disorder are present: the orientation of the aldehyde group (occupancy ratio 0.5:0.5) and of symmetry-equivalent ethyl groups [occupancy ratio 0.595 (7):0.405 (7)]. The phenyl­ene ring and the carbonyl group are essentially coplanar [C—C—C—O torsion angle = −179.0 (4)°] but the dihedral angle between the mean planes of the phenyl­ene ring and the amino group = 67.5 (2)°. This and the long [1.414 (3) Å] aniline C—N bond indicate electronic decoupling between the carbonyl and amino groups. The angle sum of 359.9 (2)° around the N atom results from steric compression-induced rehybridization.

Related literature

The title compound was prepared as an inter­mediate in the synthesis of highly solvatochromic (Detert et al., 2002 ▶; Detert & Schmitt, 2006 ▶) or acidochromic fluoro­phores (Schmitt et al., 2008 ▶, 2011 ▶). For crystal structures of anilines with a p-accetor substituent, see: Fischer et al. (2011 ▶); Moschel et al. (2011 ▶). Acceptor-substituted anilines display dual fluorescence due to the formation of TICT (twisted intra­molecular charge-transfer) states, see: Rotkiewicz et al. (1973 ▶); Okada et al. (1999 ▶). For the crystal structure of 4-dimethyl­amino­benzaldehyde, see: Gao & Zhu (2008 ▶).

Experimental

Crystal data

• C₁₇H₂₇NO

• M _r = 261.40

• Monoclinic,

• a = 11.8061 (9) Å

• b = 14.3419 (7) Å

• c = 10.7891 (8) Å

• β = 118.478 (3)°

• V = 1605.78 (19) ų

• Z = 4

• Cu Kα radiation

• μ = 0.50 mm⁻¹

• T = 173 K

• 0.50 × 0.20 × 0.05 mm

Data collection

• Enraf–Nonius CAD-4 diffractometer

• 1607 measured reflections

• 1533 independent reflections

• 1165 reflections with I > 2σ(I)

• R _int = 0.065

• 60 standard reflections every 60 min intensity decay: 3%

Refinement

• R[F ² > 2σ(F ²)] = 0.057

• wR(F ²) = 0.186

• S = 1.07

• 1533 reflections

• 117 parameters

• H-atom parameters constrained

• Δρ_max = 0.31 e Å⁻³

• Δρ_min = −0.23 e Å⁻³

Data collection: CAD-4 Software (Enraf–Nonius, 1989 ▶); cell refinement: CAD-4 Software; data reduction: CORINC (Dräger & Gattow, 1971 ▶); program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2009 ▶); software used to prepare material for publication: PLATON.

Supplementary Material

Supplementary material file. DOI: 10.1107/S1600536811047672/bt5711Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Comment

The aldehyde forms needle-shaped crystals of the monoclinic space group C2/c.The compound crystallizes in parallel layers composed of geometrical dimers with C2 symmetry and z = 2. Two modes of disorder are present. A symmetry axis through C11—C4—C1—N4 results in a C2-symmetry of the molecule - but the carboxaldehyde group is disordered (50/50). The symmetry equivalent ethyl groups are also disordered but the s.o.f. is 60/40. The planes of the amino group and the benzene ring open an angle of 67.3 (3) ° whereas the carbonyl group and the aromatic system are essentially coplanar (torsion angle C3—C4—C11—O12: -179.0 (4) °). The sum of the bond angles around the nitrogen atom in both conformers is 359.9 (2) °, corresponding to a sp² hybridization. With 1.414 (3) Å, the aniline C—N bond is much longer than the corresponding bond (1.366 (2) Å) in the sterically undisturbed dimethylaminobenzaldehyde (Gao & Zhu, 2008). This may be in part due to steric congestion, but also due to inhibited conjugation. Correspondingly, the carbonyl bond length of 1.114 (4) Å in the title compound is shorter than in the dimethylamino derivative (1.204 (2) Å, 1.212 (3) Å) and with 1.470 (4) Å the aryl-carbonyl bond C4—C11 is longer than in the reference compound (1.457 (3) Å, 1.454 (2) Å).

Experimental

4-Bromo-N,N-diethyl-2,6-diisopropylaniline (0.76 g, 2.5 mmol) was dissolved in THF (15 ml) under nitrogen in a flame-dried Schlenk tube. The solution was cooled to195 K and n-BuLi (2.5 M in heptane, 1 ml) was added dropwise. After stirring for 1 h, dry DMF (0.2 ml, 2.5 mmol) was added carefully, stirring was continued for 15 min at 195 K, and the solution was allowed to reach room temperature. Aqueous NH₄Cl (conc. 15 ml) was added and the mixture extracted with ethyl acetate (3 * 20 ml). The pooled organic solutions were dried (Na₂SO₄), concentrated in vacuo and the product was isolated via column chromatography (SiO₂, petroleum ether / ethyl acetate = 15 / 1) R_f = 0.4 (petroleum ether / ethyl acetate = 9 / 1). The aldehyde was isolated as a yellowish oil that crystallized upon standing for several days. Yield: 0.23 g (35%)

Refinement

Hydrogen atoms attached to carbons were placed at calculated positions with C—H = 0.95 Å (aromatic) or 0.98–0.99 Å (sp³ C-atom). All H atoms were refined in the riding-model approximation with isotropic displacement parameters set at 1.2–1.5 times of the U_eq of the parent atom.

Figures

Fig. 1.

View of compound I. Displacement ellipsoids are drawn at the 50% probability level. Only major conformer is shown.

Crystal data

C17H27NO	F(000) = 576
Mr = 261.40	Dx = 1.081 Mg m−3
Monoclinic, C2/c	Cu Kα radiation, λ = 1.54178 Å
Hall symbol: -C 2yc	Cell parameters from 25 reflections
a = 11.8061 (9) Å	θ = 60–70°
b = 14.3419 (7) Å	µ = 0.50 mm−1
c = 10.7891 (8) Å	T = 173 K
β = 118.478 (3)°	Needle, colourless
V = 1605.78 (19) Å3	0.50 × 0.20 × 0.05 mm
Z = 4

Data collection

Enraf–Nonius CAD-4 diffractometer	Rint = 0.065
Radiation source: rotating anode	θmax = 70.0°, θmin = 5.3°
graphite	h = 0→14
ω/2θ scans	k = 0→17
1607 measured reflections	l = −13→11
1533 independent reflections	60 standard reflections every 60 min
1165 reflections with I > 2σ(I)	intensity decay: 3%

Refinement

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.057	H-atom parameters constrained
wR(F2) = 0.186	w = 1/[σ2(Fo2) + (0.1003P)2 + 0.8224P] where P = (Fo2 + 2Fc2)/3
S = 1.07	(Δ/σ)max < 0.001
1533 reflections	Δρmax = 0.31 e Å−3
117 parameters	Δρmin = −0.23 e Å−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0061 (10)

Special details

Experimental. 1H-NMR (400 MHz, CDCl3): 9.95 (s, 1 H, CHO), 6.61 (s, 2 H, 2-H, 6-H), 3.49 (sept, 3J = 6.9 Hz, 2 H, CH (i-Pr)), 3.11 (q, 3J = 7.1 Hz, 4 H, N-CH2), 1.22 (d, 3J = 6.9 Hz, 12 H, CH3 (iPr)), 1.04 (t, 3J = 7.1 Hz, 6 H, CH3 (Et)).13C-NMR (75 MHz, CDCl3): 192.5 (CHO), 152.3 (C-4), 150.9 (C-3, C-5), 134.3 (C-1), 126.0 (C-2, C-6), 48.9 (N-CH2), 29.2 (CH (iPr), 24.5 (CH3 (iPr)), 15.2 (CH3 (Et)).IR (ATR) ν = 2963, 2928, 2869, 2723, 1696, 1594, 1568, 1457, 1365, 1268, 1170, 1104, 1065, 941, 892, 783, 724 cm-1.HR-ESI-MS: found 262.2177, calc. 262.2171 for (M+H+).

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	Occ. (<1)
C1	0.5000	0.29898 (16)	0.2500	0.0301 (6)
C2	0.49043 (16)	0.25001 (12)	0.13197 (17)	0.0329 (5)
C3	0.49237 (18)	0.15335 (13)	0.13533 (18)	0.0407 (5)
H3	0.4884	0.1198	0.0574	0.049*
C4	0.5000	0.10460 (18)	0.2500	0.0445 (7)
N5	0.5000	0.39757 (14)	0.2500	0.0394 (6)
C6	0.3927 (4)	0.4517 (2)	0.2464 (5)	0.0477 (12)	0.595 (7)
H6A	0.4284	0.5063	0.3095	0.057*	0.595 (7)
H6B	0.3471	0.4125	0.2841	0.057*	0.595 (7)
C7	0.2975 (5)	0.4852 (3)	0.1028 (5)	0.0704 (16)	0.595 (7)
H7A	0.3405	0.5274	0.0668	0.106*	0.595 (7)
H7B	0.2275	0.5186	0.1082	0.106*	0.595 (7)
H7C	0.2620	0.4318	0.0391	0.106*	0.595 (7)
C6A	0.3813 (6)	0.4420 (4)	0.1519 (7)	0.0511 (19)	0.405 (7)
H6C	0.3242	0.3953	0.0827	0.061*	0.405 (7)
H6D	0.3999	0.4910	0.0997	0.061*	0.405 (7)
C7A	0.3127 (8)	0.4849 (6)	0.2250 (9)	0.084 (3)	0.405 (7)
H7D	0.2754	0.4355	0.2570	0.126*	0.405 (7)
H7E	0.2439	0.5260	0.1593	0.126*	0.405 (7)
H7F	0.3741	0.5212	0.3064	0.126*	0.405 (7)
C8	0.47720 (17)	0.29910 (13)	0.00066 (18)	0.0384 (5)
H8	0.4765	0.3678	0.0159	0.046*
C9	0.5913 (2)	0.27726 (19)	−0.0249 (2)	0.0577 (7)
H9A	0.6715	0.2966	0.0573	0.087*
H9B	0.5812	0.3111	−0.1085	0.087*
H9C	0.5941	0.2101	−0.0399	0.087*
C10	0.3504 (2)	0.27324 (18)	−0.1286 (2)	0.0535 (6)
H10A	0.3516	0.2070	−0.1502	0.080*
H10B	0.3397	0.3108	−0.2094	0.080*
H10C	0.2786	0.2853	−0.1093	0.080*
C11	0.5000	0.0021 (2)	0.2500	0.0730 (11)
H11	0.4960	−0.0251	0.1677	0.088*	0.50
O12	0.5039 (6)	−0.0493 (2)	0.3294 (5)	0.1012 (16)	0.50

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
C1	0.0306 (11)	0.0327 (12)	0.0323 (12)	0.000	0.0193 (9)	0.000
C2	0.0347 (9)	0.0379 (10)	0.0326 (9)	0.0009 (7)	0.0213 (7)	0.0008 (6)
C3	0.0542 (11)	0.0377 (10)	0.0404 (10)	0.0018 (8)	0.0309 (9)	−0.0059 (7)
C4	0.0589 (17)	0.0334 (14)	0.0487 (15)	0.000	0.0317 (13)	0.000
N5	0.0500 (13)	0.0301 (11)	0.0438 (12)	0.000	0.0272 (10)	0.000
C6	0.051 (2)	0.0404 (19)	0.046 (2)	0.0115 (16)	0.0187 (17)	−0.0043 (15)
C7	0.062 (3)	0.062 (3)	0.073 (3)	0.008 (2)	0.020 (2)	0.017 (2)
C6A	0.063 (4)	0.037 (3)	0.054 (4)	0.012 (3)	0.028 (3)	0.008 (2)
C7A	0.068 (5)	0.082 (5)	0.092 (6)	0.020 (4)	0.031 (4)	−0.032 (4)
C8	0.0425 (10)	0.0476 (11)	0.0311 (9)	−0.0020 (8)	0.0225 (8)	0.0020 (7)
C9	0.0548 (13)	0.0874 (17)	0.0472 (12)	−0.0001 (11)	0.0374 (10)	0.0050 (11)
C10	0.0519 (12)	0.0748 (15)	0.0329 (10)	−0.0049 (10)	0.0194 (9)	0.0035 (9)
C11	0.112 (3)	0.0387 (17)	0.083 (3)	0.000	0.059 (2)	0.000
O12	0.195 (5)	0.0416 (19)	0.101 (3)	−0.003 (2)	0.098 (3)	0.0176 (19)

Geometric parameters (Å, °)

C1—C2	1.411 (2)	C6A—C7A	1.505 (10)
C1—C2i	1.411 (2)	C6A—H6C	0.9900
C1—N5	1.414 (3)	C6A—H6D	0.9900
C2—C3	1.387 (3)	C7A—H7D	0.9800
C2—C8	1.522 (2)	C7A—H7E	0.9800
C3—C4	1.386 (2)	C7A—H7F	0.9800
C3—H3	0.9500	C8—C10	1.527 (3)
C4—C3i	1.386 (2)	C8—C9	1.530 (3)
C4—C11	1.470 (4)	C8—H8	1.0000
N5—C6Ai	1.441 (6)	C9—H9A	0.9800
N5—C6A	1.441 (6)	C9—H9B	0.9800
N5—C6i	1.470 (4)	C9—H9C	0.9800
N5—C6	1.470 (4)	C10—H10A	0.9800
C6—C7	1.495 (6)	C10—H10B	0.9800
C6—H6A	0.9900	C10—H10C	0.9800
C6—H6B	0.9900	C11—O12i	1.114 (4)
C7—H7A	0.9800	C11—O12	1.114 (4)
C7—H7B	0.9800	C11—H11	0.9500
C7—H7C	0.9800
C2—C1—C2i	120.3 (2)	C7A—C6A—H6D	109.2
C2—C1—N5	119.86 (11)	H6C—C6A—H6D	107.9
C2i—C1—N5	119.86 (11)	C6A—C7A—H7D	109.5
C3—C2—C1	118.74 (16)	C6A—C7A—H7E	109.5
C3—C2—C8	118.68 (15)	H7D—C7A—H7E	109.5
C1—C2—C8	122.58 (17)	C6A—C7A—H7F	109.5
C4—C3—C2	121.39 (17)	H7D—C7A—H7F	109.5
C4—C3—H3	119.3	H7E—C7A—H7F	109.5
C2—C3—H3	119.3	C2—C8—C10	111.02 (15)
C3i—C4—C3	119.4 (2)	C2—C8—C9	111.38 (15)
C3i—C4—C11	120.29 (12)	C10—C8—C9	110.43 (16)
C3—C4—C11	120.29 (12)	C2—C8—H8	108.0
C1—N5—C6Ai	116.2 (2)	C10—C8—H8	108.0
C1—N5—C6A	116.2 (2)	C9—C8—H8	108.0
C6Ai—N5—C6A	127.5 (5)	C8—C9—H9A	109.5
C1—N5—C6i	121.86 (16)	C8—C9—H9B	109.5
C6A—N5—C6i	108.1 (3)	H9A—C9—H9B	109.5
C1—N5—C6	121.86 (16)	C8—C9—H9C	109.5
C6Ai—N5—C6	108.1 (3)	H9A—C9—H9C	109.5
C6i—N5—C6	116.3 (3)	H9B—C9—H9C	109.5
N5—C6—C7	114.2 (4)	C8—C10—H10A	109.5
N5—C6—H6A	108.7	C8—C10—H10B	109.5
C7—C6—H6A	108.7	H10A—C10—H10B	109.5
N5—C6—H6B	108.7	C8—C10—H10C	109.5
C7—C6—H6B	108.7	H10A—C10—H10C	109.5
H6A—C6—H6B	107.6	H10B—C10—H10C	109.5
N5—C6A—C7A	112.0 (6)	O12i—C11—C4	131.4 (3)
N5—C6A—H6C	109.2	O12—C11—C4	131.4 (3)
C7A—C6A—H6C	109.2	O12—C11—H11	114.3
N5—C6A—H6D	109.2	C4—C11—H11	114.3
C2i—C1—C2—C3	−0.85 (12)	C1—N5—C6—C7	−97.8 (3)
N5—C1—C2—C3	179.15 (12)	C6Ai—N5—C6—C7	123.5 (4)
C2i—C1—C2—C8	178.76 (17)	C6A—N5—C6—C7	−4.4 (4)
N5—C1—C2—C8	−1.24 (17)	C6i—N5—C6—C7	82.2 (3)
C1—C2—C3—C4	1.7 (2)	C1—N5—C6A—C7A	107.0 (5)
C8—C2—C3—C4	−177.89 (13)	C6Ai—N5—C6A—C7A	−73.0 (5)
C2—C3—C4—C3i	−0.89 (12)	C6i—N5—C6A—C7A	−111.7 (5)
C2—C3—C4—C11	179.11 (12)	C6—N5—C6A—C7A	−2.0 (4)
C2—C1—N5—C6Ai	−112.2 (3)	C3—C2—C8—C10	61.2 (2)
C2i—C1—N5—C6Ai	67.8 (3)	C1—C2—C8—C10	−118.38 (18)
C2—C1—N5—C6A	67.8 (3)	C3—C2—C8—C9	−62.3 (2)
C2i—C1—N5—C6A	−112.2 (3)	C1—C2—C8—C9	118.10 (18)
C2—C1—N5—C6i	−67.7 (2)	C3i—C4—C11—O12i	−179.0 (4)
C2i—C1—N5—C6i	112.3 (2)	C3—C4—C11—O12i	1.0 (4)
C2—C1—N5—C6	112.3 (2)	C3i—C4—C11—O12	1.0 (4)
C2i—C1—N5—C6	−67.7 (2)	C3—C4—C11—O12	−179.0 (4)

Symmetry codes: (i) −x+1, y, −z+1/2.