organic compounds
Ethyl 2-[N-(tert-butylsulfinyl)carbamoyl]benzoate
aCNRS, LCC, 205 route de Narbonne, F-31077 Toulouse, France, bUniversité de Toulouse, UPS, INPT, LCC, F31077 Toulouse, France, and cMinakem, 145 Chemin des Lilas, F-59310 Beuvry-La-Foret, France
*Correspondence e-mail: emmanuel.gras@lcc-toulouse.fr
The title compound, C14H19NO4S, was obtained in quantitative yield by Lewis acid-catalysed of a phtalimide precursor. An intramolecular C—H⋯O hydrogen bond occurs. In the crystal, centrosymmetric dimers are formed by pairs of N—H⋯O hydrogen bonds between the sulfinyl O atoms and the carbamoyl N—H group of a neighboring molecule. C—H⋯O interactions feature in the crystal structure.
Related literature
For a related compound, see: Harpp & Back (1973). For hydrogen-bond motifs and graph-set notation, see: Etter (1990); Bernstein et al. (1995). For potential applications of the title compound in the synthesis of enones, see: Wang et al. (2005). For standard bond lengths, see: Allen et al. (1987).
Experimental
Crystal data
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Refinement
|
Data collection: CrysAlis PRO (Oxford Diffraction, 2010); cell CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: WinGX (Farrugia, 1999).
Supporting information
https://doi.org/10.1107/S1600536811047027/im2332sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536811047027/im2332Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S1600536811047027/im2332Isup3.cml
To a suspension of 100 mg (0.398 mmol) of tert-butylsulfinyl phtalimide in 5 ml of ethanol stirred at room temperature is added a solution of 24 mg (0.04 mmol) of samarium(III) trifluoromethanesulfonate in 5 ml of ethanol. After 0.5 h of stirring at room temperature a complete solubilization is observed and a full conversion is confirmed by TLC (cyclohexane/diethyl ether: 2/8). After concentration of the reaction mixture under reduced pressure, the remainings are diluted with 10 ml of dichloromethane and washed twice with water (2x5 ml). The aqueous phases are extracted twice with 10 ml of dichloromethane. The combined organic phases are dried of sodium sulfate and concentrated to dryness under reduced pressure to give 118.1 mg (100% yield) of a white solid. Crystals of (I) suitable for X-ray diffraction were grown overnight at -20 °C in a 95/5 Diethyl ether/dichloromethane mixture.
All H atoms attached to C atoms were fixed geometrically and treated as riding with C—H = 0.98 Å (methyl) or 0.95 Å (aromatic) or 0.97 Å (methylene) with Uiso(H) = 1.2Ueq(C). The H attached to nitrogen has been located on difference Fourier and its coordinates were refined using N—H restraints of 0.88 (1) Å with Uiso(H) = 1.2Ueq(N).
In the course of our studies on tert-butylsulfinyl phtalimide we have uncovered an unusual access to ethyl 2-(tert-butylsulfinylcarbamoyl)benzoate (I) based on the
activation (for example by Samarium (III) salts) of one C=O bond of the phtalimide moiety. The title compound has been obtained quantitative yield.Interestingly (I) exhibits one hydrogen donor (NH) and 5 electronegative atoms featuring available lone pairs that therefore should be able to act as hydrogen acceptors (4 oxygen and one sulfur). The combination of these donors and acceptors can induce a wide variety of hydrogen-bond patterns. A preferred one can be indicative of higher H-bond acceptor ability of one group.
Moreover, these features are of interest for potential applications in organocatalysis. Indeed acidic imide hydrogen atoms have been shown to favour organocatalytic processes in the formation of enones under mild reaction conditions. (Wang et al. 2005)
The
clearly establishes N–H···O contacts between the O atoms of the sulfinyl groups and the NH groups since the N···O distance falls by more than 0.2Å below he sum of the van-der-Waals radii of the atoms involved. This is strongly indicative of the presence of two intermolecular hydrogen bonds. From that point, a cyclic dimer is observed with a R22(8) graph set (Fig. 2). Interestingly although isographic to the sulfinyl group (i.e. it has the same graph set but is chemically different), the carbonyl group of the amide is not involved in any hydrogen bond. This is a clear illustration of the higher polar character of the S=O bond making the sulfinyl oxygen a better H-bond acceptor than its carbonyl counterpart.The R22(8) graph set is a six bonds ring system exhibiting a chair like conformation in which the two tert-butyl groups are in axial positions and the two carbamoyl units in equatorial positions (Fig. 2). An unexpectedly small distance (in the range of the sum of the van-der-Waals radii) is observed between the oxygen of the carboxyl group of the ester and the nitrogen. The observed conformation might be minimizing the repulsive coulombic interaction and steric repulsions. All bond lengths and angles are otherwise normal. (Allen et al. 1987) Finally as the reaction has been carried out on racemic tert-butylsulfinyl phtalimide, (I) has been obtained as a racemate. It can be seen from the
that (I) crystallizes as a (i.e. the two enantiomers forming dimers in the crystal lattice) indicating that no happens (formation of conglomerates).For a related compound, see: Harpp & Back (1973). For hydrogen-bond motifs and graph-set notation, see: Etter (1990); Bernstein et al. (1995). For potential applications of the title compound in the synthesis of enones, see: Wang et al. (2005).
For related literature, see: Allen et al. (1987).
Data collection: CrysAlis PRO (Oxford Diffraction, 2010); cell
CrysAlis PRO (Oxford Diffraction, 2010); data reduction: CrysAlis PRO (Oxford Diffraction, 2010); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: WinGX (Farrugia, 1999).C14H19NO4S | F(000) = 632 |
Mr = 297.37 | Dx = 1.317 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 9878 reflections |
a = 11.7881 (3) Å | θ = 2.9–29.0° |
b = 9.0056 (2) Å | µ = 0.23 mm−1 |
c = 16.3296 (4) Å | T = 180 K |
β = 120.091 (2)° | Block, colourless |
V = 1499.91 (7) Å3 | 0.4 × 0.25 × 0.03 mm |
Z = 4 |
Oxford-Diffraction Gemini diffractometer | 2744 independent reflections |
Radiation source: Enhance (Mo) X-ray Source | 2334 reflections with I > 2s(I) |
Graphite monochromator | Rint = 0.022 |
ω scan | θmax = 25.4°, θmin = 2.9° |
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2010) | h = −14→14 |
Tmin = 0.930, Tmax = 0.990 | k = −10→10 |
15187 measured reflections | l = −19→18 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.029 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.088 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.12 | w = 1/[σ2(Fo2) + (0.0508P)2 + 0.2576P] where P = (Fo2 + 2Fc2)/3 |
2744 reflections | (Δ/σ)max < 0.001 |
188 parameters | Δρmax = 0.50 e Å−3 |
1 restraint | Δρmin = −0.28 e Å−3 |
C14H19NO4S | V = 1499.91 (7) Å3 |
Mr = 297.37 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 11.7881 (3) Å | µ = 0.23 mm−1 |
b = 9.0056 (2) Å | T = 180 K |
c = 16.3296 (4) Å | 0.4 × 0.25 × 0.03 mm |
β = 120.091 (2)° |
Oxford-Diffraction Gemini diffractometer | 2744 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2010) | 2334 reflections with I > 2s(I) |
Tmin = 0.930, Tmax = 0.990 | Rint = 0.022 |
15187 measured reflections |
R[F2 > 2σ(F2)] = 0.029 | 1 restraint |
wR(F2) = 0.088 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.12 | Δρmax = 0.50 e Å−3 |
2744 reflections | Δρmin = −0.28 e Å−3 |
188 parameters |
Experimental. 1H NMR (CDCl3, 400?MHz): 8.01 (s, 1H); 7.61–7.55 (m, 4H); 4.40 (q, J 7.2?Hz, 2H); 1.40 (t, J 7.2?Hz, 3H); 1.33 (s, 9H). 13C NMR (CDCl3, 100.6?MHz, T= 233?K): 171.8; 165.6; 136.1; 132.5; 130.5; 130.1; 129.1; 127.6; 62.0; 57.8; 22.4; 14.0. MS (DCI, NH3): 315.0; IR (cm-1): 3068; 2971; 1710; 1688; 1428; 1247; 1062; 885;805; 703. MP: 129–131 °C. |
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. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.9715 (2) | 0.8337 (3) | 0.54534 (15) | 0.0587 (6) | |
H1A | 0.8812 | 0.8463 | 0.4934 | 0.088* | |
H1B | 1.0281 | 0.8081 | 0.5195 | 0.088* | |
H1C | 1.0021 | 0.9265 | 0.5813 | 0.088* | |
C2 | 0.97629 (19) | 0.7127 (2) | 0.60890 (14) | 0.0419 (4) | |
H2A | 0.9451 | 0.6184 | 0.5733 | 0.05* | |
H2B | 1.0673 | 0.6982 | 0.6614 | 0.05* | |
C3 | 0.87361 (14) | 0.65483 (17) | 0.69751 (10) | 0.0262 (3) | |
C4 | 0.79014 (14) | 0.71356 (17) | 0.73504 (10) | 0.0241 (3) | |
C5 | 0.79902 (17) | 0.86253 (18) | 0.76008 (12) | 0.0328 (4) | |
H5 | 0.8554 | 0.9269 | 0.7507 | 0.039* | |
C6 | 0.72634 (19) | 0.9176 (2) | 0.79856 (13) | 0.0409 (4) | |
H6 | 0.7317 | 1.0197 | 0.8146 | 0.049* | |
C7 | 0.64604 (18) | 0.8236 (2) | 0.81356 (12) | 0.0386 (4) | |
H7 | 0.5965 | 0.8611 | 0.8403 | 0.046* | |
C8 | 0.63737 (16) | 0.67464 (19) | 0.78977 (11) | 0.0296 (4) | |
H8 | 0.5822 | 0.6106 | 0.8006 | 0.036* | |
C9 | 0.70872 (14) | 0.61845 (16) | 0.75018 (10) | 0.0224 (3) | |
C10 | 0.68801 (14) | 0.45713 (16) | 0.72159 (10) | 0.0224 (3) | |
C11 | 0.68034 (15) | 0.22686 (16) | 0.52516 (10) | 0.0255 (3) | |
C12 | 0.67874 (18) | 0.35133 (19) | 0.46180 (12) | 0.0344 (4) | |
H12A | 0.7299 | 0.3216 | 0.4322 | 0.052* | |
H12B | 0.7172 | 0.441 | 0.4998 | 0.052* | |
H12C | 0.5881 | 0.3717 | 0.4125 | 0.052* | |
C13 | 0.81679 (16) | 0.20074 (19) | 0.60975 (12) | 0.0350 (4) | |
H13A | 0.8755 | 0.1665 | 0.5875 | 0.052* | |
H13B | 0.8121 | 0.1253 | 0.6512 | 0.052* | |
H13C | 0.8505 | 0.2937 | 0.645 | 0.052* | |
C14 | 0.62431 (19) | 0.08368 (19) | 0.46900 (13) | 0.0410 (4) | |
H14A | 0.5337 | 0.1007 | 0.4186 | 0.062* | |
H14B | 0.6261 | 0.0055 | 0.5114 | 0.062* | |
H14C | 0.6772 | 0.053 | 0.441 | 0.062* | |
N1 | 0.63756 (12) | 0.43515 (13) | 0.62653 (8) | 0.0215 (3) | |
H101 | 0.6177 (16) | 0.5099 (14) | 0.5890 (10) | 0.026* | |
O1 | 0.89198 (11) | 0.75638 (12) | 0.64578 (8) | 0.0332 (3) | |
O2 | 0.92023 (11) | 0.53207 (12) | 0.71343 (9) | 0.0365 (3) | |
O3 | 0.70681 (12) | 0.35692 (12) | 0.77681 (7) | 0.0352 (3) | |
O4 | 0.44238 (10) | 0.30802 (11) | 0.49210 (7) | 0.0278 (3) | |
S1 | 0.57360 (4) | 0.27051 (4) | 0.57391 (2) | 0.02149 (13) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0548 (13) | 0.0834 (16) | 0.0556 (12) | 0.0132 (12) | 0.0408 (11) | 0.0184 (12) |
C2 | 0.0404 (10) | 0.0503 (11) | 0.0517 (11) | 0.0016 (8) | 0.0355 (9) | −0.0005 (9) |
C3 | 0.0211 (8) | 0.0294 (9) | 0.0285 (8) | −0.0069 (6) | 0.0128 (6) | −0.0054 (6) |
C4 | 0.0244 (8) | 0.0265 (8) | 0.0219 (7) | −0.0029 (6) | 0.0119 (6) | −0.0028 (6) |
C5 | 0.0379 (9) | 0.0297 (9) | 0.0376 (9) | −0.0096 (7) | 0.0239 (8) | −0.0078 (7) |
C6 | 0.0533 (12) | 0.0303 (9) | 0.0514 (11) | −0.0087 (8) | 0.0353 (10) | −0.0161 (8) |
C7 | 0.0458 (11) | 0.0393 (10) | 0.0439 (10) | −0.0035 (8) | 0.0325 (9) | −0.0124 (8) |
C8 | 0.0317 (9) | 0.0352 (9) | 0.0277 (8) | −0.0055 (7) | 0.0192 (7) | −0.0033 (7) |
C9 | 0.0215 (7) | 0.0265 (8) | 0.0162 (7) | −0.0014 (6) | 0.0073 (6) | −0.0015 (6) |
C10 | 0.0196 (7) | 0.0265 (8) | 0.0226 (7) | −0.0011 (6) | 0.0116 (6) | 0.0008 (6) |
C11 | 0.0301 (8) | 0.0229 (8) | 0.0280 (8) | 0.0013 (6) | 0.0180 (7) | −0.0009 (6) |
C12 | 0.0413 (10) | 0.0367 (10) | 0.0358 (9) | 0.0056 (7) | 0.0272 (8) | 0.0076 (7) |
C13 | 0.0321 (9) | 0.0341 (9) | 0.0390 (9) | 0.0102 (7) | 0.0180 (8) | 0.0038 (7) |
C14 | 0.0496 (11) | 0.0339 (9) | 0.0465 (10) | −0.0044 (8) | 0.0294 (9) | −0.0145 (8) |
N1 | 0.0263 (7) | 0.0169 (6) | 0.0204 (6) | −0.0014 (5) | 0.0111 (5) | 0.0015 (5) |
O1 | 0.0352 (7) | 0.0354 (6) | 0.0407 (6) | 0.0007 (5) | 0.0276 (6) | 0.0012 (5) |
O2 | 0.0307 (6) | 0.0293 (6) | 0.0570 (8) | 0.0010 (5) | 0.0275 (6) | −0.0006 (5) |
O3 | 0.0486 (7) | 0.0286 (6) | 0.0267 (6) | −0.0010 (5) | 0.0177 (5) | 0.0059 (5) |
O4 | 0.0244 (6) | 0.0241 (5) | 0.0290 (6) | −0.0026 (4) | 0.0090 (5) | −0.0013 (4) |
S1 | 0.0251 (2) | 0.01767 (19) | 0.0227 (2) | −0.00142 (13) | 0.01277 (16) | 0.00053 (13) |
C1—C2 | 1.486 (3) | C9—C10 | 1.508 (2) |
C1—H1A | 0.98 | C10—O3 | 1.2150 (18) |
C1—H1B | 0.98 | C10—N1 | 1.3699 (19) |
C1—H1C | 0.98 | C11—C12 | 1.519 (2) |
C2—O1 | 1.451 (2) | C11—C13 | 1.524 (2) |
C2—H2A | 0.99 | C11—C14 | 1.527 (2) |
C2—H2B | 0.99 | C11—S1 | 1.8373 (16) |
C3—O2 | 1.2036 (19) | C12—H12A | 0.98 |
C3—O1 | 1.3343 (19) | C12—H12B | 0.98 |
C3—C4 | 1.493 (2) | C12—H12C | 0.98 |
C4—C5 | 1.391 (2) | C13—H13A | 0.98 |
C4—C9 | 1.398 (2) | C13—H13B | 0.98 |
C5—C6 | 1.384 (2) | C13—H13C | 0.98 |
C5—H5 | 0.95 | C14—H14A | 0.98 |
C6—C7 | 1.380 (3) | C14—H14B | 0.98 |
C6—H6 | 0.95 | C14—H14C | 0.98 |
C7—C8 | 1.386 (2) | N1—S1 | 1.6898 (12) |
C7—H7 | 0.95 | N1—H101 | 0.860 (9) |
C8—C9 | 1.388 (2) | O4—S1 | 1.4898 (11) |
C8—H8 | 0.95 | ||
C2—C1—H1A | 109.5 | O3—C10—C9 | 123.02 (13) |
C2—C1—H1B | 109.5 | N1—C10—C9 | 113.63 (12) |
H1A—C1—H1B | 109.5 | C12—C11—C13 | 112.22 (14) |
C2—C1—H1C | 109.5 | C12—C11—C14 | 111.10 (13) |
H1A—C1—H1C | 109.5 | C13—C11—C14 | 110.86 (14) |
H1B—C1—H1C | 109.5 | C12—C11—S1 | 111.09 (11) |
O1—C2—C1 | 107.28 (15) | C13—C11—S1 | 106.33 (10) |
O1—C2—H2A | 110.3 | C14—C11—S1 | 104.89 (11) |
C1—C2—H2A | 110.3 | C11—C12—H12A | 109.5 |
O1—C2—H2B | 110.3 | C11—C12—H12B | 109.5 |
C1—C2—H2B | 110.3 | H12A—C12—H12B | 109.5 |
H2A—C2—H2B | 108.5 | C11—C12—H12C | 109.5 |
O2—C3—O1 | 124.39 (15) | H12A—C12—H12C | 109.5 |
O2—C3—C4 | 124.08 (14) | H12B—C12—H12C | 109.5 |
O1—C3—C4 | 111.52 (13) | C11—C13—H13A | 109.5 |
C5—C4—C9 | 119.75 (14) | C11—C13—H13B | 109.5 |
C5—C4—C3 | 119.63 (14) | H13A—C13—H13B | 109.5 |
C9—C4—C3 | 120.52 (13) | C11—C13—H13C | 109.5 |
C6—C5—C4 | 120.43 (15) | H13A—C13—H13C | 109.5 |
C6—C5—H5 | 119.8 | H13B—C13—H13C | 109.5 |
C4—C5—H5 | 119.8 | C11—C14—H14A | 109.5 |
C7—C6—C5 | 119.79 (16) | C11—C14—H14B | 109.5 |
C7—C6—H6 | 120.1 | H14A—C14—H14B | 109.5 |
C5—C6—H6 | 120.1 | C11—C14—H14C | 109.5 |
C6—C7—C8 | 120.32 (16) | H14A—C14—H14C | 109.5 |
C6—C7—H7 | 119.8 | H14B—C14—H14C | 109.5 |
C8—C7—H7 | 119.8 | C10—N1—S1 | 122.17 (10) |
C7—C8—C9 | 120.43 (15) | C10—N1—H101 | 120.2 (11) |
C7—C8—H8 | 119.8 | S1—N1—H101 | 115.6 (11) |
C9—C8—H8 | 119.8 | C3—O1—C2 | 116.06 (13) |
C8—C9—C4 | 119.29 (14) | O4—S1—N1 | 104.78 (6) |
C8—C9—C10 | 116.97 (14) | O4—S1—C11 | 106.78 (7) |
C4—C9—C10 | 123.68 (13) | N1—S1—C11 | 100.38 (7) |
O3—C10—N1 | 123.21 (14) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H101···O4i | 0.86 (1) | 2.00 (1) | 2.857 (2) | 173 (2) |
C5—H5···O2ii | 0.95 | 2.59 | 3.469 (3) | 155 |
C13—H13C···O2 | 0.98 | 2.37 | 3.345 (2) | 174 |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+2, y+1/2, −z+3/2. |
Experimental details
Crystal data | |
Chemical formula | C14H19NO4S |
Mr | 297.37 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 180 |
a, b, c (Å) | 11.7881 (3), 9.0056 (2), 16.3296 (4) |
β (°) | 120.091 (2) |
V (Å3) | 1499.91 (7) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.23 |
Crystal size (mm) | 0.4 × 0.25 × 0.03 |
Data collection | |
Diffractometer | Oxford-Diffraction Gemini |
Absorption correction | Multi-scan (CrysAlis PRO; Oxford Diffraction, 2010) |
Tmin, Tmax | 0.930, 0.990 |
No. of measured, independent and observed [I > 2s(I)] reflections | 15187, 2744, 2334 |
Rint | 0.022 |
(sin θ/λ)max (Å−1) | 0.602 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.029, 0.088, 1.12 |
No. of reflections | 2744 |
No. of parameters | 188 |
No. of restraints | 1 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.50, −0.28 |
Computer programs: CrysAlis PRO (Oxford Diffraction, 2010), SIR92 (Altomare et al., 1994), SHELXL97 (Sheldrick, 2008), Mercury (Macrae et al., 2008), WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H101···O4i | 0.86 (1) | 2.00 (1) | 2.857 (2) | 173 (2) |
C5—H5···O2ii | 0.9500 | 2.5900 | 3.469 (3) | 155.00 |
C13—H13C···O2 | 0.9800 | 2.3700 | 3.345 (2) | 174.00 |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+2, y+1/2, −z+3/2. |
Acknowledgements
Minakem is acknowledged for PhD funding (for AH). Dr J.-C. Daran is warmly acknowledged for his kind help during the preparation of this paper.
References
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In the course of our studies on tert-butylsulfinyl phtalimide we have uncovered an unusual access to ethyl 2-(tert-butylsulfinylcarbamoyl)benzoate (I) based on the Lewis acid activation (for example by Samarium (III) salts) of one C=O bond of the phtalimide moiety. The title compound has been obtained quantitative yield.
Interestingly (I) exhibits one hydrogen donor (NH) and 5 electronegative atoms featuring available lone pairs that therefore should be able to act as hydrogen acceptors (4 oxygen and one sulfur). The combination of these donors and acceptors can induce a wide variety of hydrogen-bond patterns. A preferred one can be indicative of higher H-bond acceptor ability of one group.
Moreover, these features are of interest for potential applications in organocatalysis. Indeed acidic imide hydrogen atoms have been shown to favour organocatalytic processes in the formation of enones under mild reaction conditions. (Wang et al. 2005)
The crystal structure clearly establishes N–H···O contacts between the O atoms of the sulfinyl groups and the NH groups since the N···O distance falls by more than 0.2Å below he sum of the van-der-Waals radii of the atoms involved. This is strongly indicative of the presence of two intermolecular hydrogen bonds. From that point, a cyclic dimer is observed with a R22(8) graph set (Fig. 2). Interestingly although isographic to the sulfinyl group (i.e. it has the same graph set but is chemically different), the carbonyl group of the amide is not involved in any hydrogen bond. This is a clear illustration of the higher polar character of the S=O bond making the sulfinyl oxygen a better H-bond acceptor than its carbonyl counterpart.
The R22(8) graph set is a six bonds ring system exhibiting a chair like conformation in which the two tert-butyl groups are in axial positions and the two carbamoyl units in equatorial positions (Fig. 2). An unexpectedly small distance (in the range of the sum of the van-der-Waals radii) is observed between the oxygen of the carboxyl group of the ester and the nitrogen. The observed conformation might be minimizing the repulsive coulombic interaction and steric repulsions. All bond lengths and angles are otherwise normal. (Allen et al. 1987) Finally as the reaction has been carried out on racemic tert-butylsulfinyl phtalimide, (I) has been obtained as a racemate. It can be seen from the crystal structure that (I) crystallizes as a racemic compound (i.e. the two enantiomers forming dimers in the crystal lattice) indicating that no spontaneous resolution happens (formation of conglomerates).