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Crystal structure of 2-oxo-2-phenyl­ethyl diiso­propyl­carbamate

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aInstitute of Integrated Natural Sciences, University Koblenz - Landau, Universitätsstr. 1, 56070 Koblenz, Germany, and bInstitute of Inorganic and Analytical Chemistry, Friedrich-Schiller-University Jena, Humboldtstr. 8, 07743 Jena, Germany
*Correspondence e-mail: Imhof@uni-koblenz.de

Edited by M. Zeller, Purdue University, USA (Received 21 June 2021; accepted 6 July 2021; online 13 July 2021)

In the mol­ecular structure of the title compound, C15H21NO3, the urethane function and the benzoyl group are almost perpendicular to each other [dihedral angle 88.97 (5)°]. In the crystal structure, infinite supra­molecular layers in the bc plane are formed by weak C—H⋯O hydrogen bonds.

1. Chemical context

Phenacyl and desyl compounds have been a subject of inter­est for many years due to their use as photoremovable protecting groups (PPGs) (Givens et al., 2012[Givens, R. S., Rubina, M. & Wirz, J. (2012). Photochem. Photobiol. Sci. 11, 472-488.]; Kammari et al., 2007[Kammari, L., Plíštil, L., Wirz, J. & Klán, P. (2007). Photochem. Photobiol. Sci. 6, 50-56.]; Klán et al., 2013[Klán, P., Šolomek, T., Bochet, C. G., Blanc, A., Givens, R., Rubina, M., Popik, V., Kostikov, A. & Wirz, J. (2013). Chem. Rev. 113, 119-191.]; Sheehan & Umezawa, 1973[Sheehan, J. C. & Umezawa, K. (1973). J. Org. Chem. 38, 3771-3774.]). Carbamates are used for the protection of carb­oxy­lic acids and may also act as suitable protecting groups for amines (Speckmeier et al., 2018[Speckmeier, E., Klimkait, M. & Zeitler, K. (2018). J. Org. Chem. 83, 3738-3745.]). Speckmeier and co-workers synthesized several phenacyl urethanes, but the protection of diiso­propyl­amine by a phenacyl group has not been reported so far. The title compound was synthesized according to reported routes (Speckmeier et al., 2018[Speckmeier, E., Klimkait, M. & Zeitler, K. (2018). J. Org. Chem. 83, 3738-3745.]).

[Scheme 1]

2. Structural commentary

As expected, the carbamate functional moiety (N1/C3/O3/O2) is essentially planar (maximum deviation of 0.01 Å for C3). The same is true for the benzoyl group (C1/O1/C10–C15, maximum deviation of 0.05 Å for O1). These two planes subtend a dihedral angle of 88.97 (5)° and therefore an almost perpendicular arrangement (Fig. 1[link]). Otherwise, the bond lengths and angles are of expected values with C3—N1 [1.348 (2) Å] and C3—O2 [1.368 (2) Å] being slightly shorter than a typical C—O or C—N single bond due to the partial double-bond character of the respective bonds in a carbamate.

[Figure 1]
Figure 1
Mol­ecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level.

3. Supra­molecular features

The crystal structure of the title compound features weak hydrogen bonds (Desiraju & Steiner, 2001[Desiraju, G. R. & Steiner, T. (2001). The Weak Hydrogen Bond. Oxford Science Publications.]) of the C—H⋯O type, as shown in Table 1[link]. The inter­action C5—H5B⋯O3 links mol­ecules of the title compound into infinite chains parallel to the c-axis direction. Additional C2—H2B⋯O1 and C9—H9B⋯O2 inter­actions link these infinite chains to a supra­molecular sheet parallel to the bc plane (Fig. 2[link]). The latter inter­action is accompanied by a short C9—H9B⋯C3 contact, which makes the contact look like a non-classical hydrogen bond towards the π-system of a C=O double bond, again showing the partial double-bond character of the respective bond.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C2—H2B⋯O1i 0.99 2.70 3.605 (2) 152
C5—H5B⋯O3ii 0.98 2.62 3.578 (2) 167
C9—H9B⋯O2iii 0.98 2.68 3.599 (2) 157
Symmetry codes: (i) [x, y-1, z]; (ii) [x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]; (iii) x, y+1, z.
[Figure 2]
Figure 2
Crystal structure of the title compound showing layers of mol­ecules along the bc plane that are built up by C—H⋯O hydrogen bonds.

4. Database survey

In the CSD (ConQuest Version 2020.3.0; Groom et al., 2016[Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171-179.]), only one other carbamate with a CH2–C(O)-Ph group attached to the carbamate oxygen atom is reported (NIWQUI; Jiang et al., 2019[Jiang, H., Zhang, H., Xiong, W., Qi, C., Wu, W., Wang, L. & Cheng, R. (2019). Org. Lett. 21, 1125-1129.]). The respective compound shows a di­ethyl­amino group and a p-chloro­phenyl substituent instead of the diiso­propyl­amino group and the non-substituted phenyl group in the title compound. In contrast to the title compound, the carbamate plane and the benzoyl plane are almost coplanar. The carbonyl oxygen atoms show numerous short contacts towards different C—H groups of neighboring mol­ecules, leading to a dense three-dimensional network.

5. Synthesis and crystallization

Diiso­propyl­amine (0.05 mol, 5.05 g) and 1 equiv. of cesium carbonate (0.05 mol, 16.55 g) were placed in a Schlenk tube and dissolved in anhydrous DMSO (150 mL). The tube was sealed with a septum and two balloons filled with CO2 were bubbled through the reaction mixture within one h while stirring. After the addition of CO2, 1.1 equiv. of 2-bromo-1-phenyl­ethan-1-one (0.055 mol, 10.95 g) dissolved in a small amount of DMSO was added in one portion. The consumption of 2-bromo-1-phenyl­ethan-1-one was monitored by TLC and after 30 min the reaction mixture was poured on ice to quench the reaction. After extraction with di­chloro­methane (3×), the combined organic phases were washed with brine, separated and dried over Na2SO4. The solvent was removed in vacuo and the crude product was recrystallized from n-hexa­ne/ethanol (4:1) to afford the title compound (12.90 g; 98%) as a colorless solid, m.p. 347.5°C. 1H NMR (500 MHz, CDCl3) [ppm]: δ = 7.90 (dd, 2H), 7.55 (ddt, 1H), 7.45 (dd, J = 8.4, 7.1 Hz, 2H), 5.33 (s, 2H), 3.97 (hept, 2H), 1.25 (d, 12H); 13C NMR (126 MHz, CDCl3) [ppm]: δ = 193.91 (C=O), 154.80 (NC=O), 134.69, 133.65, 128.84, 127.83 (Car), 66.36 (O=C—O), 46.32 [(H3C)2CH–], 20.99 [(H3C)2CH–].

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link]. All hydrogen atoms were placed in idealized positions (C—H = 0.95–0.99Å) and refined using a riding model with isotropic displacement parameters calculated as Uiso(H) = 1.2×Ueq(C) for methyl­ene and hydrogen atoms of the phenyl group or 1.5×Ueq(C) for methyl groups.

Table 2
Experimental details

Crystal data
Chemical formula C15H21NO3
Mr 263.33
Crystal system, space group Monoclinic, P21/c
Temperature (K) 133
a, b, c (Å) 18.4574 (8), 5.7020 (2), 14.8058 (6)
β (°) 113.468 (1)
V3) 1429.33 (10)
Z 4
Radiation type Mo Kα
μ (mm−1) 0.09
Crystal size (mm) 0.10 × 0.10 × 0.08
 
Data collection
Diffractometer Nonius KappaCCD
Absorption correction Multi-scan (SADABS; Krause et al., 2015[Krause, L., Herbst-Irmer, R., Sheldrick, G. M. & Stalke, D. (2015). J. Appl. Cryst. 48, 3-10.])
Tmin, Tmax 0.674, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections 13968, 3280, 2464
Rint 0.040
(sin θ/λ)max−1) 0.649
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.049, 0.113, 1.04
No. of reflections 3280
No. of parameters 177
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.27, −0.21
Computer programs: COLLECT (Nonius 1998[Nonius (1998). COLLECT. Nonius BV, Delft, The Netherlands.]), DENZO (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]), SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), SHELXL2018/3 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]), ORTEP-3 (Farrugia, 2012[Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849-854.]) and Mercury (Macrae et al., 2020[Macrae, C. F., Sovago, I., Cottrell, S. J., Galek, P. T. A., McCabe, P., Pidcock, E., Platings, M., Shields, G. P., Stevens, J. S., Towler, M. & Wood, P. A. (2020). J. Appl. Cryst. 53, 226-235.]).

Supporting information


Computing details top

Data collection: COLLECT (Nonius 1998); cell refinement: DENZO (Otwinowski & Minor, 1997); data reduction: DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015); molecular graphics: ORTEP-3 (Farrugia, 2012); software used to prepare material for publication: Mercury (Macrae et al., 2020).

2-oxo-2-phenylethyl diisopropylcarbamate top
Crystal data top
C15H21NO3F(000) = 568
Mr = 263.33Dx = 1.224 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 18.4574 (8) ÅCell parameters from 13968 reflections
b = 5.7020 (2) Åθ = 2.8–27.5°
c = 14.8058 (6) ŵ = 0.09 mm1
β = 113.468 (1)°T = 133 K
V = 1429.33 (10) Å3Prism, colourless
Z = 40.10 × 0.10 × 0.08 mm
Data collection top
Nonius KappaCCD
diffractometer
2464 reflections with I > 2σ(I)
phi + ω – scansRint = 0.040
Absorption correction: multi-scan
(SADABS; Krause et al., 2015)
θmax = 27.5°, θmin = 2.8°
Tmin = 0.674, Tmax = 0.746h = 2323
13968 measured reflectionsk = 57
3280 independent reflectionsl = 1918
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.049H-atom parameters constrained
wR(F2) = 0.113 w = 1/[σ2(Fo2) + (0.0368P)2 + 0.6743P]
where P = (Fo2 + 2Fc2)/3
S = 1.04(Δ/σ)max < 0.001
3280 reflectionsΔρmax = 0.27 e Å3
177 parametersΔρmin = 0.21 e Å3
0 restraintsExtinction correction: SHELXL2018/3 (Sheldrick 2015)
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0093 (16)
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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.38605 (6)0.7949 (2)0.38826 (9)0.0338 (3)
O20.27936 (6)0.4581 (2)0.32610 (8)0.0280 (3)
O30.24228 (6)0.6202 (2)0.17458 (8)0.0285 (3)
N10.17054 (7)0.6836 (3)0.26709 (9)0.0285 (3)
C10.41005 (8)0.6137 (3)0.36687 (11)0.0234 (3)
C20.35448 (8)0.4079 (3)0.32488 (12)0.0257 (3)
H2A0.3485140.3773900.2564500.031*
H2B0.3768660.2655600.3644610.031*
C30.23136 (8)0.5945 (3)0.24965 (11)0.0249 (3)
C40.16762 (9)0.6747 (4)0.36534 (12)0.0371 (4)
H40.2116330.5705860.4077180.044*
C50.18152 (13)0.9155 (5)0.41331 (15)0.0605 (7)
H5A0.2287940.9857870.4098620.091*
H5B0.1889870.8998950.4823860.091*
H5C0.1357341.0159300.3786310.091*
C60.09072 (11)0.5665 (4)0.36026 (15)0.0452 (5)
H6A0.0465720.6703050.3229930.068*
H6B0.0930710.5459400.4270830.068*
H6C0.0830000.4137590.3274310.068*
C70.11069 (9)0.8271 (3)0.19039 (11)0.0278 (4)
H70.0741780.8872350.2200310.033*
C80.06055 (9)0.6780 (3)0.10240 (12)0.0319 (4)
H8A0.0196020.7759180.0543760.048*
H8B0.0356430.5511610.1244220.048*
H8C0.0941280.6109900.0717290.048*
C90.14496 (11)1.0413 (3)0.16096 (14)0.0405 (5)
H9A0.1762970.9917620.1242300.061*
H9B0.1787891.1267410.2201910.061*
H9C0.1019401.1436370.1194430.061*
C100.49370 (8)0.5861 (3)0.37810 (11)0.0248 (3)
C110.51983 (9)0.3863 (3)0.34607 (12)0.0315 (4)
H110.4843540.2605460.3172320.038*
C120.59781 (10)0.3710 (4)0.35634 (13)0.0420 (5)
H120.6155860.2346650.3343880.050*
C130.64925 (10)0.5519 (4)0.39804 (13)0.0478 (6)
H130.7025290.5403310.4048750.057*
C140.62389 (10)0.7512 (4)0.43024 (13)0.0437 (5)
H140.6597360.8762520.4588720.052*
C150.54637 (9)0.7686 (3)0.42078 (12)0.0327 (4)
H150.5291430.9049670.4434060.039*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0316 (6)0.0311 (6)0.0386 (7)0.0050 (5)0.0140 (5)0.0076 (5)
O20.0204 (5)0.0369 (6)0.0260 (6)0.0011 (5)0.0087 (4)0.0069 (5)
O30.0261 (5)0.0375 (7)0.0229 (6)0.0009 (5)0.0108 (4)0.0031 (5)
N10.0201 (6)0.0433 (8)0.0219 (7)0.0018 (6)0.0081 (5)0.0037 (6)
C10.0248 (7)0.0269 (8)0.0182 (7)0.0041 (6)0.0080 (6)0.0014 (6)
C20.0227 (7)0.0278 (8)0.0264 (8)0.0023 (6)0.0095 (6)0.0021 (6)
C30.0199 (7)0.0310 (8)0.0211 (7)0.0038 (6)0.0055 (6)0.0007 (6)
C40.0257 (8)0.0627 (13)0.0251 (8)0.0034 (8)0.0125 (7)0.0044 (8)
C50.0611 (13)0.0909 (18)0.0325 (10)0.0377 (13)0.0217 (10)0.0224 (11)
C60.0487 (11)0.0512 (12)0.0475 (11)0.0061 (9)0.0314 (9)0.0003 (9)
C70.0218 (7)0.0317 (9)0.0269 (8)0.0026 (6)0.0065 (6)0.0008 (7)
C80.0251 (7)0.0352 (9)0.0289 (8)0.0006 (7)0.0041 (7)0.0019 (7)
C90.0418 (10)0.0327 (10)0.0417 (10)0.0035 (8)0.0108 (8)0.0002 (8)
C100.0227 (7)0.0335 (9)0.0174 (7)0.0036 (6)0.0069 (6)0.0035 (6)
C110.0278 (8)0.0404 (10)0.0257 (8)0.0066 (7)0.0101 (7)0.0001 (7)
C120.0323 (9)0.0672 (13)0.0276 (9)0.0201 (9)0.0133 (7)0.0047 (9)
C130.0209 (8)0.0923 (17)0.0311 (10)0.0091 (10)0.0111 (7)0.0159 (10)
C140.0265 (8)0.0666 (14)0.0318 (10)0.0123 (9)0.0051 (7)0.0068 (9)
C150.0288 (8)0.0404 (10)0.0252 (8)0.0038 (7)0.0068 (7)0.0003 (7)
Geometric parameters (Å, º) top
O1—C11.2149 (19)C7—C91.517 (2)
O2—C31.3684 (18)C7—C81.522 (2)
O2—C21.4230 (17)C7—H71.0000
O3—C31.2148 (18)C8—H8A0.9800
N1—C31.348 (2)C8—H8B0.9800
N1—C71.4764 (19)C8—H8C0.9800
N1—C41.478 (2)C9—H9A0.9800
C1—C101.494 (2)C9—H9B0.9800
C1—C21.519 (2)C9—H9C0.9800
C2—H2A0.9900C10—C151.392 (2)
C2—H2B0.9900C10—C111.392 (2)
C4—C51.520 (3)C11—C121.389 (2)
C4—C61.522 (2)C11—H110.9500
C4—H41.0000C12—C131.371 (3)
C5—H5A0.9800C12—H120.9500
C5—H5B0.9800C13—C141.384 (3)
C5—H5C0.9800C13—H130.9500
C6—H6A0.9800C14—C151.385 (2)
C6—H6B0.9800C14—H140.9500
C6—H6C0.9800C15—H150.9500
C3—O2—C2114.64 (12)N1—C7—C8111.27 (13)
C3—N1—C7119.12 (13)C9—C7—C8112.63 (14)
C3—N1—C4122.37 (13)N1—C7—H7106.3
C7—N1—C4117.83 (13)C9—C7—H7106.3
O1—C1—C10121.89 (14)C8—C7—H7106.3
O1—C1—C2120.45 (14)C7—C8—H8A109.5
C10—C1—C2117.64 (13)C7—C8—H8B109.5
O2—C2—C1110.00 (13)H8A—C8—H8B109.5
O2—C2—H2A109.7C7—C8—H8C109.5
C1—C2—H2A109.7H8A—C8—H8C109.5
O2—C2—H2B109.7H8B—C8—H8C109.5
C1—C2—H2B109.7C7—C9—H9A109.5
H2A—C2—H2B108.2C7—C9—H9B109.5
O3—C3—N1125.75 (14)H9A—C9—H9B109.5
O3—C3—O2122.46 (14)C7—C9—H9C109.5
N1—C3—O2111.72 (13)H9A—C9—H9C109.5
N1—C4—C5111.30 (16)H9B—C9—H9C109.5
N1—C4—C6111.37 (14)C15—C10—C11119.50 (15)
C5—C4—C6111.69 (16)C15—C10—C1118.42 (15)
N1—C4—H4107.4C11—C10—C1122.07 (14)
C5—C4—H4107.4C12—C11—C10119.92 (17)
C6—C4—H4107.4C12—C11—H11120.0
C4—C5—H5A109.5C10—C11—H11120.0
C4—C5—H5B109.5C13—C12—C11120.25 (18)
H5A—C5—H5B109.5C13—C12—H12119.9
C4—C5—H5C109.5C11—C12—H12119.9
H5A—C5—H5C109.5C12—C13—C14120.29 (16)
H5B—C5—H5C109.5C12—C13—H13119.9
C4—C6—H6A109.5C14—C13—H13119.9
C4—C6—H6B109.5C13—C14—C15120.11 (18)
H6A—C6—H6B109.5C13—C14—H14119.9
C4—C6—H6C109.5C15—C14—H14119.9
H6A—C6—H6C109.5C14—C15—C10119.93 (18)
H6B—C6—H6C109.5C14—C15—H15120.0
N1—C7—C9113.40 (13)C10—C15—H15120.0
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2B···O1i0.992.703.605 (2)152
C5—H5B···O3ii0.982.623.578 (2)167
C9—H9B···O2iii0.982.683.599 (2)157
Symmetry codes: (i) x, y1, z; (ii) x, y+3/2, z+1/2; (iii) x, y+1, z.
 

Acknowledgements

Financial support of the PhD project of VM by Lohmann GmbH & Co. KG, Neuwied, Germany, is gratefully acknowledged.

References

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