Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270109019544/gg3197sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270109019544/gg3197IIsup2.hkl |
CCDC reference: 742251
To a solution of the racemic secondary amine, (I) (Bartsch & Schwarz, 1983) (0.32 g, 2 mmol), in absolute pyridine (25 ml) at 277 K under an argon atmosphere were added benzoyl chloride dropwise (75 µl, 2 equivalents) and a crystal (Size? Mass?) of DMAP [Please define]. The mixture was stirred for 14 h at room temperature and the solvent and reagent excess evaporated under reduced pressure. The residue was dissolved in CH2Cl2 (50 ml), washed with water (3 × 10 ml), isolated, dried over MgSO4, and finally concentrated under reduced pressure. The resulting gum solidified on standing in the dark and was crystallized from hot 96% EtOH to give white monocrystals [yield 78%, 0.412 g; m.p. 434–435 K (Tottoli [An instrument?])]. Spectroscopic analysis: IR (NaCl neat, ν, cm-1): 3056, 2948, 2361, 2350, 2240, 1657, 1495, 1370, 1266; 1H NMR (250 MHz, CDCl3, δ, p.p.m.): 3.81 (dd, 1H, J = 2.9 and 13.9 Hz, H13), 4.74 [dd, 1H, J = 3.6 and 13.9 Hz, H15A(B)], 5.3 [t, 1H, J = 3.3 and 13.9 Hz, H15B(A)], 6.7–6.8 (m, 2H, Ar), 6.95–7.1 (m, 2H, Ar), 7.35–7.65 (m, 5H, Bz); ES—MS+: 265.2 (100) [M + H]+, 238.2 (17) [M - CN]+. Elemental analysis, calculated for C16H12N2O2: C 72.72, H 4.58, N 10.60%; found: C 73.02, H 4.48, N 10.66%.
Least-squares refinement, based on |F|, were carried out using the program MoPro (Guillot et al., 2001; Jelsch et al., 2005) using the ELMAM electron-density database (Zarychta et al., 2007). Refinement of F against all reflections. No reflection had a negative intensity. The weighted R-factor wR and goodness of fit S are based on F, and conventional R-factors R are based on F. The threshold expression of F2 > 2σ(F2) is used only for calculating R-factors(gt) and is not relevant to the choice of reflections for refinement. The reflection weights were set equal to 7.29/σ2(Fo). The Uiso(H) values were constrained to be 1.2Ueq of the parent atom.
Data collection: CrysAlis CCD (Oxford Diffraction, 2008); cell refinement: CrysAlis RED (Oxford Diffraction, 2008); data reduction: CrysAlis RED (Oxford Diffraction, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: MoPro (Guillot et al., 2001; Jelsch et al., 2005); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: MoPro (Guillot et al., 2001; Jelsch et al., 2005).
C16H12N2O2 | F(000) = 552 |
Mr = 264.28 | Dx = 1.322 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 21257 reflections |
a = 11.8920 (4) Å | θ = 3.1–34.9° |
b = 7.3590 (2) Å | µ = 0.09 mm−1 |
c = 15.886 (1) Å | T = 100 K |
β = 107.200 (4)° | Prismatic, colourless |
V = 1328.06 (11) Å3 | 0.35 × 0.22 × 0.17 mm |
Z = 4 |
Oxford Diffraction Xcalibur2 diffractometer | 4047 independent reflections |
Radiation source: Enhance (Mo) X-ray Source | 2724 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.032 |
Detector resolution: 10.4508 pixels mm-1 | θmax = 30.6°, θmin = 2.7° |
ω scans | h = 0→17 |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2008) | k = 0→10 |
Tmin = 0.950, Tmax = 1.000 | l = −22→21 |
53523 measured reflections |
Refinement on F | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.061 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.023 | H-atom parameters constrained |
S = 1.01 | w = 1/[7.29σ2(Fo2)] |
4047 reflections | (Δ/σ)max = 0.029 |
181 parameters | Δρmax = 0.14 e Å−3 |
13 restraints | Δρmin = −0.10 e Å−3 |
C16H12N2O2 | V = 1328.06 (11) Å3 |
Mr = 264.28 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 11.8920 (4) Å | µ = 0.09 mm−1 |
b = 7.3590 (2) Å | T = 100 K |
c = 15.886 (1) Å | 0.35 × 0.22 × 0.17 mm |
β = 107.200 (4)° |
Oxford Diffraction Xcalibur2 diffractometer | 4047 independent reflections |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2008) | 2724 reflections with I > 2σ(I) |
Tmin = 0.950, Tmax = 1.000 | Rint = 0.032 |
53523 measured reflections |
R[F2 > 2σ(F2)] = 0.061 | 13 restraints |
wR(F2) = 0.023 | H-atom parameters constrained |
S = 1.01 | Δρmax = 0.14 e Å−3 |
4047 reflections | Δρmin = −0.10 e Å−3 |
181 parameters |
Experimental. Absorption correction: CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.32.29 (release 10-06-2008 CrysAlis171.NET) (compiled Jun 10 2008,16:49:55) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.1941 (1) | 0.0050 (2) | 0.21563 (9) | 0.0190 (2) | |
C2 | 0.1190 (1) | 0.1310 (2) | 0.23588 (9) | 0.0254 (2) | |
C3 | −0.0009 (1) | 0.1235 (2) | 0.1938 (1) | 0.0309 (2) | |
C4 | −0.0470 (1) | −0.0096 (2) | 0.13133 (10) | 0.0284 (3) | |
C5 | 0.0273 (1) | −0.1360 (2) | 0.11021 (10) | 0.0281 (3) | |
C6 | 0.1477 (1) | −0.1284 (2) | 0.15188 (10) | 0.0241 (2) | |
C7 | 0.3192 (1) | 0.0642 (2) | 0.40680 (9) | 0.0167 (2) | |
C8 | 0.2445 (1) | −0.0775 (2) | 0.41318 (9) | 0.0213 (2) | |
C9 | 0.1901 (1) | −0.0780 (2) | 0.48008 (10) | 0.0243 (3) | |
C10 | 0.2145 (1) | 0.0605 (2) | 0.54282 (10) | 0.0245 (2) | |
C11 | 0.2941 (1) | 0.1969 (2) | 0.53963 (9) | 0.0236 (2) | |
C12 | 0.3470 (1) | 0.1978 (2) | 0.47180 (10) | 0.0184 (2) | |
C13 | 0.4725 (1) | 0.3478 (2) | 0.40127 (9) | 0.0210 (2) | |
C14 | 0.3251 (1) | 0.0183 (2) | 0.25258 (9) | 0.0167 (2) | |
C15 | 0.4888 (1) | 0.1629 (2) | 0.36372 (9) | 0.0198 (2) | |
C16 | 0.3878 (1) | 0.4611 (2) | 0.3346 (1) | 0.0269 (3) | |
N1 | 0.3182 (1) | 0.5489 (2) | 0.28530 (9) | 0.0387 (2) | |
N2 | 0.37379 (10) | 0.0715 (2) | 0.33823 (7) | 0.0199 (2) | |
O1 | 0.38754 (8) | −0.0041 (1) | 0.20429 (6) | 0.0243 (2) | |
O2 | 0.42847 (8) | 0.3315 (1) | 0.47577 (6) | 0.0260 (2) | |
H2 | 0.15592 | 0.23887 | 0.28220 | 0.03045* | |
H3 | −0.05868 | 0.21761 | 0.21320 | 0.03710* | |
H4 | −0.14091 | −0.01898 | 0.09955 | 0.03406* | |
H5 | −0.01020 | −0.24125 | 0.06250 | 0.03372* | |
H6 | 0.20901 | −0.22495 | 0.13855 | 0.02887* | |
H8 | 0.22739 | −0.18725 | 0.36566 | 0.02554* | |
H9 | 0.13282 | −0.19104 | 0.48257 | 0.02921* | |
H10 | 0.17729 | 0.06457 | 0.59732 | 0.02943* | |
H11 | 0.31722 | 0.30276 | 0.58915 | 0.02835* | |
H13 | 0.55840 | 0.41625 | 0.42296 | 0.02514* | |
H15A | 0.51960 | 0.17382 | 0.30562 | 0.02378* | |
H15B | 0.54957 | 0.08009 | 0.41410 | 0.02378* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0192 (9) | 0.0200 (10) | 0.0156 (9) | 0.0037 (8) | 0.0033 (7) | −0.0030 (6) |
C2 | 0.0217 (6) | 0.029 (1) | 0.0222 (10) | 0.0066 (9) | 0.0026 (7) | −0.0052 (8) |
C3 | 0.0225 (6) | 0.040 (1) | 0.0262 (10) | 0.0088 (9) | 0.0010 (7) | −0.0064 (7) |
C4 | 0.0203 (10) | 0.037 (1) | 0.0239 (10) | −0.0026 (9) | 0.0022 (7) | −0.0010 (7) |
C5 | 0.0224 (6) | 0.031 (1) | 0.027 (1) | −0.0031 (9) | 0.0031 (7) | −0.0057 (8) |
C6 | 0.0227 (6) | 0.0254 (10) | 0.0210 (9) | −0.0017 (8) | 0.0032 (6) | −0.0066 (6) |
C7 | 0.0179 (7) | 0.0146 (9) | 0.0161 (5) | −0.0044 (8) | 0.0051 (3) | −0.0001 (7) |
C8 | 0.0238 (9) | 0.020 (1) | 0.0185 (9) | −0.0052 (8) | 0.0087 (7) | −0.0023 (7) |
C9 | 0.0258 (10) | 0.026 (1) | 0.0200 (9) | −0.0056 (9) | 0.0088 (7) | −0.0004 (8) |
C10 | 0.0282 (9) | 0.025 (1) | 0.0183 (9) | −0.0068 (7) | 0.0090 (7) | −0.0021 (8) |
C11 | 0.0286 (9) | 0.025 (1) | 0.0167 (9) | −0.0061 (7) | 0.0104 (8) | −0.0019 (7) |
C12 | 0.0223 (9) | 0.0160 (9) | 0.0154 (9) | −0.0023 (6) | 0.0066 (7) | −0.0025 (7) |
C13 | 0.0233 (9) | 0.023 (1) | 0.0158 (8) | 0.0005 (9) | 0.0090 (6) | 0.0026 (8) |
C14 | 0.0179 (9) | 0.0174 (9) | 0.0135 (6) | 0.0005 (8) | 0.0057 (5) | −0.0022 (6) |
C15 | 0.0169 (7) | 0.020 (1) | 0.0205 (9) | −0.0015 (6) | 0.0047 (7) | −0.0004 (7) |
C16 | 0.030 (1) | 0.023 (1) | 0.027 (1) | 0.0037 (7) | 0.0154 (7) | 0.0016 (7) |
N1 | 0.0388 (9) | 0.032 (1) | 0.043 (1) | 0.0111 (7) | 0.0173 (7) | 0.0116 (7) |
N2 | 0.0179 (5) | 0.0248 (8) | 0.0152 (4) | −0.0030 (5) | 0.0047 (3) | −0.0037 (5) |
O1 | 0.0238 (6) | 0.0296 (7) | 0.0188 (6) | 0.0007 (6) | 0.0107 (4) | −0.0036 (5) |
O2 | 0.0366 (7) | 0.0220 (7) | 0.0191 (6) | −0.0111 (5) | 0.0156 (5) | −0.0064 (5) |
O1—C14 | 1.227 (1) | C5—C6 | 1.390 (2) |
O2—C12 | 1.370 (2) | C5—H5 | 1.083 |
O2—C13 | 1.434 (2) | C6—H6 | 1.083 |
N2—C7 | 1.424 (2) | C7—C8 | 1.393 (2) |
N2—C14 | 1.369 (2) | C7—C12 | 1.393 (2) |
N2—C15 | 1.470 (2) | C8—C9 | 1.398 (2) |
C13—C16 | 1.483 (2) | C8—H8 | 1.083 |
N1—C16 | 1.155 (2) | C9—C10 | 1.395 (2) |
C1—C2 | 1.389 (2) | C9—H9 | 1.083 |
C1—C6 | 1.401 (2) | C10—C11 | 1.391 (2) |
C1—C14 | 1.497 (2) | C10—H10 | 1.083 |
C2—C3 | 1.385 (2) | C11—C12 | 1.399 (2) |
C2—H2 | 1.083 | C11—H11 | 1.083 |
C3—C4 | 1.387 (2) | C13—C15 | 1.521 (2) |
C3—H3 | 1.083 | C13—H13 | 1.099 |
C4—C5 | 1.391 (2) | C15—H15A | 1.092 |
C4—H4 | 1.083 | C15—H15B | 1.092 |
C7—N2—C14 | 126.5 (2) | C4—C5—C6 | 119.8 (1) |
C7—N2—C15 | 113.8 (1) | C4—C5—H5 | 119.2 |
C14—N2—C15 | 119.4 (1) | C5—C6—H6 | 122.6 |
O1—C14—N2 | 120.2 (2) | C5—C4—H4 | 119.1 |
O1—C14—C1 | 119.9 (1) | C6—C5—H5 | 121.0 |
N2—C14—C1 | 119.6 (1) | C6—C1—C14 | 118.1 (1) |
C13—C16—N1 | 176.6 (2) | C7—C8—C9 | 120.4 (2) |
C13—C15—N2 | 107.5 (1) | C7—C8—H8 | 120.0 |
C15—C13—O2 | 111.7 (1) | C7—C12—C11 | 120.4 (2) |
C16—C13—O2 | 107.4 (1) | C12—C11—H11 | 118.7 |
C15—C13—C16 | 111.2 (1) | C8—C9—C10 | 119.7 (2) |
C7—C12—O2 | 123.4 (1) | C8—C9—H9 | 117.9 |
C8—C7—N2 | 121.9 (1) | C8—C7—C12 | 119.4 (1) |
C11—C12—O2 | 116.2 (1) | C9—C10—C11 | 120.1 (1) |
C12—O2—C13 | 116.6 (1) | C9—C10—H10 | 122.9 |
C12—C7—N2 | 118.6 (2) | C9—C8—H8 | 119.6 |
C1—C2—C3 | 120.1 (2) | C10—C11—C12 | 119.8 (2) |
C1—C2—H2 | 119.2 | C10—C11—H11 | 121.5 |
C1—C6—C5 | 120.2 (2) | C10—C9—H9 | 122.4 |
C1—C6—H6 | 117.2 | C11—C10—H10 | 116.9 |
C2—C3—C4 | 120.4 (2) | C13—C15—H15A | 112.3 |
C2—C3—H3 | 119.1 | C13—C15—H15B | 110.2 |
C2—C1—C6 | 119.5 (2) | C15—C13—H13 | 108.6 |
C2—C1—C14 | 122.1 (1) | C16—C13—H13 | 109.8 |
C3—C2—H2 | 120.6 | N2—C15—H15A | 108.6 |
C3—C4—C5 | 120.0 (2) | N2—C15—H15B | 107.9 |
C3—C4—H4 | 120.9 | O2—C13—H13 | 108.2 |
C4—C3—H3 | 120.3 | H15A—C15—H15B | 110.2 |
C1—C14—N2—C7 | 20.9 (1) | C8—C7—N2—C15 | −149.8 (1) |
C1—C14—N2—C15 | −152.4 (1) | C8—C7—C12—O2 | 173.3 (1) |
C2—C1—C14—N2 | 39.2 (1) | C8—C7—C12—C11 | −4.4 (1) |
C7—N2—C14—O1 | −165.0 (1) | C9—C10—C11—C12 | 1.9 (1) |
C7—N2—C15—C13 | −52.8 (1) | C9—C10—C11—H11 | −177.4 |
C8—C7—N2—C14 | 36.6 (1) | C9—C8—C7—N2 | −178.4 (1) |
C7—C12—O2—C13 | 9.7 (1) | C9—C8—C7—C12 | 5.2 (1) |
C12—O2—C13—C16 | 84.3 (1) | C10—C11—C12—O2 | −177.0 (1) |
C12—O2—C13—C15 | −37.9 (1) | C10—C9—C8—H8 | 178.2 |
C12—C7—N2—C15 | 26.6 (1) | C11—C10—C9—H9 | 176.2 |
C13—C15—N2—C14 | 121.4 (1) | C11—C12—O2—C13 | −172.5 (1) |
C1—C2—C3—C4 | 0.09 (13) | C11—C12—C7—N2 | 179.1 (1) |
C1—C2—C3—H3 | 176.3 | C12—O2—C13—H13 | −157.3 |
C1—C6—C5—C4 | 0.7 (1) | C12—C11—C10—H10 | 178.9 |
C1—C6—C5—H5 | −177.8 | C12—C7—N2—C14 | −147.0 (1) |
C2—C3—C4—C5 | −0.4 (1) | C12—C7—C8—H8 | −175.5 |
C2—C3—C4—H4 | 178.1 | C14—N2—C15—H15A | −0.4 |
C2—C1—C6—C5 | −1.0 (1) | C14—N2—C15—H15B | −119.8 |
C2—C1—C6—H6 | −179.3 | C14—C1—C2—H2 | −2.9 |
C2—C1—C14—O1 | −135.0 (2) | C14—C1—C6—H6 | 7.1 |
C3—C2—C1—C6 | 0.6 (1) | C15—N2—C14—O1 | 21.7 (1) |
C3—C2—C1—C14 | 173.9 (1) | C16—C13—C15—N2 | −61.2 (1) |
C3—C4—C5—C6 | 0.00 (15) | C16—C13—C15—H15A | 58.2 |
C3—C4—C5—H5 | 178.5 | C16—C13—C15—H15B | −178.5 |
C4—C3—C2—H2 | 176.8 | N2—C7—C8—H8 | 0.9 |
C4—C5—C6—H6 | 179.0 | N2—C7—C12—O2 | −3.2 (1) |
C5—C6—C1—C14 | −174.5 (1) | N2—C15—C13—O2 | 58.8 (1) |
C5—C4—C3—H3 | −176.5 | N2—C15—C13—H13 | 178.0 |
C6—C5—C4—H4 | −178.5 | O2—C12—C11—H11 | 2.3 |
C6—C1—C2—H2 | −176.2 | O2—C13—C15—H15A | 178.1 |
C6—C1—C14—O1 | 38.4 (1) | O2—C13—C15—H15B | −58.6 |
C6—C1—C14—N2 | −147.5 (1) | H2—C2—C3—H3 | −7.0 |
C7—N2—C15—H15A | −174.5 | H3—C3—C4—H4 | 2.0 |
C7—N2—C15—H15B | 66.1 | H4—C4—C5—H5 | 0.0 |
C7—C8—C9—C10 | −2.5 (1) | H5—C5—C6—H6 | 0.5 |
C7—C8—C9—H9 | −179.9 | H8—C8—C9—H9 | 0.8 |
C7—C12—C11—C10 | 0.9 (1) | H9—C9—C10—H10 | −0.6 |
C7—C12—C11—H11 | −179.8 | H10—C10—C11—H11 | −0.4 |
C8—C9—C10—C11 | −1.0 (1) | H13—C13—C15—H15A | −62.7 |
C8—C9—C10—H10 | −177.9 | H13—C13—C15—H15B | 60.6 |
D—H···A | D—H | H···A | D···A | D—H···A |
C11—H11···O1i | 1.08 | 2.31 | 3.387 (2) | 172 |
C13—H13···O1ii | 1.10 | 2.37 | 2.902 (2) | 108 |
C13—H13···O2iii | 1.10 | 2.43 | 3.068 (2) | 115 |
C15—H15B···Cgiv | 1.09 | 2.57 | 3.633 (2) | 165 |
Symmetry codes: (i) x, −y+1/2, z+1/2; (ii) −x+1, y+1/2, −z+1/2; (iii) −x+1, −y+1, −z+1; (iv) −x+1, −y, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C16H12N2O2 |
Mr | 264.28 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 100 |
a, b, c (Å) | 11.8920 (4), 7.3590 (2), 15.886 (1) |
β (°) | 107.200 (4) |
V (Å3) | 1328.06 (11) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.35 × 0.22 × 0.17 |
Data collection | |
Diffractometer | Oxford Diffraction Xcalibur2 diffractometer |
Absorption correction | Multi-scan (CrysAlis RED; Oxford Diffraction, 2008) |
Tmin, Tmax | 0.950, 1.000 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 53523, 4047, 2724 |
Rint | 0.032 |
(sin θ/λ)max (Å−1) | 0.717 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.061, 0.023, 1.01 |
No. of reflections | 4047 |
No. of parameters | 181 |
No. of restraints | 13 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.14, −0.10 |
Computer programs: CrysAlis CCD (Oxford Diffraction, 2008), CrysAlis RED (Oxford Diffraction, 2008), SHELXS97 (Sheldrick, 2008), MoPro (Guillot et al., 2001; Jelsch et al., 2005), SHELXTL (Sheldrick, 2008).
O1—C14 | 1.227 (1) | N2—C14 | 1.369 (2) |
O2—C12 | 1.370 (2) | N2—C15 | 1.470 (2) |
O2—C13 | 1.434 (2) | C13—C16 | 1.483 (2) |
N2—C7 | 1.424 (2) | N1—C16 | 1.155 (2) |
C7—N2—C14 | 126.5 (2) | N2—C14—C1 | 119.6 (1) |
C7—N2—C15 | 113.8 (1) | C13—C16—N1 | 176.6 (2) |
C14—N2—C15 | 119.4 (1) | C13—C15—N2 | 107.5 (1) |
O1—C14—N2 | 120.2 (2) | C15—C13—O2 | 111.7 (1) |
O1—C14—C1 | 119.9 (1) | C16—C13—O2 | 107.4 (1) |
C1—C14—N2—C7 | 20.9 (1) | C7—C12—O2—C13 | 9.7 (1) |
C1—C14—N2—C15 | −152.4 (1) | C12—O2—C13—C16 | 84.3 (1) |
C2—C1—C14—N2 | 39.2 (1) | C12—O2—C13—C15 | −37.9 (1) |
C7—N2—C14—O1 | −165.0 (1) | C12—C7—N2—C15 | 26.6 (1) |
C7—N2—C15—C13 | −52.8 (1) | C13—C15—N2—C14 | 121.4 (1) |
C8—C7—N2—C14 | 36.6 (1) |
D—H···A | D—H | H···A | D···A | D—H···A |
C11—H11···O1i | 1.083 | 2.310 | 3.387 (2) | 172.35 |
C13—H13···O1ii | 1.099 | 2.369 | 2.902 (2) | 107.90 |
C13—H13···O2iii | 1.099 | 2.431 | 3.068 (2) | 115.43 |
C15—H15B···Cgiv | 1.092 | 2.567 | 3.633 (2) | 165.33 |
Symmetry codes: (i) x, −y+1/2, z+1/2; (ii) −x+1, y+1/2, −z+1/2; (iii) −x+1, −y+1, −z+1; (iv) −x+1, −y, −z+1. |
1,4-Benzoxazines and their derivatives have attracted much attention over the past few decades (Bartsch & Schwarz, 1982). Amongst these systems cyano-substituted oxazines have been extensively studied (Bartsch & Schwarz, 1983) and cycloaddition reactions with the cyano group reviewed (Myers & Sircar, 1970). More recently, [3 + 2] cycloadditions of donor–acceptor cyclopropanes and nitriles have found interesting applications in the field of glycal chemistry (Yu & Pagenkopf, 2003). Recently, as part of a more complex 3,4-dihydropyrrole sugar-fused synthesis, we isolated the title N-acylated oxine, (II), from the known racemic oxine, (I) (Bartsch & Schwarz, 1983).
The molecular structure of (II) exists in a half-chair conformation, as depicted with the atomic numbering scheme in Fig. 1. The amide atom N2 is almost exactly in the plane defined by three neighbouring C atoms (C7, C14 and C15), with all four atoms within 0.05 Å of the plane. The sum of the valence angles around the N atom of 359.7° demonstrates clear sp2 hybridization (328° for sp3 and 360° for sp2). The other geometric parameters of (II) (Table 1) are normal and compare well with those found in other crystal structures (Bartsch & Schwarz, 1983; Black et al., 1987; Garbauskas et al., 1985; Heine et al., 1988; Feng et al., 2007). Compound (II) also exhibits a slight shortening of the carbonyl-N bond (1.369 Å), indicative of partial double-bond character; this is typical behaviour for amides.
The crystal structure of (II) is presented in Fig. 2. Molecules of (II) are linked into a three-dimensional framework by three weak C–H···O hydrogen bonds (Table 2). [A C—H···π interaction is shown in Fig. 2 - please give brief details here.]
Initially, in the independent atom model (IAM) refinement, a conventional spherical neutral atom model was applied. Scale factors, atomic positions and displacement parameters for all atoms were refined using the MOPRO program (Guillot et al., 2001; Jelsch et al., 2005) until convergence. In the experimental library multipolar atom model (ELMAM) refinement, the same parameters were varied but a multipolar charged atom model was applied. The electron-density parameters were transferred from the ELMAM library (Pichon-Pesme et al., 2004; Zarychta et al., 2007) and subsequently kept fixed. Riding constraints on H-atom isotropic displacement parameters were applied similarly in both refinements, which were carried out with the same diffraction data and using all reflections. The H–X distances were constrained to standard values in neutron diffraction studies (Allen, 1986) in the IAM and ELMAM refinements. The ELMAM refinement shows a slight improvement in statistical indexes when compared with the IAM refinement. The I>2σ(I) crystallographic factors are reduced from 7.32 to 6.09% for R(F) and from 2.22 to 2.19% for wR2(F). The minimum and maximum peaks in the residual electron density are -0.095 and +0.148 e Å-3 after the IAM refinement, and -0.103 and +0.139 e Å-3 after the ELMAN refinement. The improvement is not significant and indicates that the random noise in the residual Fourier map is here larger than the effect of not modelling the bonding electron density.
The largest effect of the multipole transfer on the crystallographic structure is observed on the atomic thermal motion (Jelsch et al., 1998). The average value of Ueq (geometric mean of eigenvalues Ui) derived from the IAM refinement is 0.0247 Å2, which is slightly higher than the value of 0.0218 Å2 from the ELMAM refinement. The correlation coefficient between both Ueq sets is only 95%. With the IAM spherical atom model, the displacement parameters are incorrect as they incorporate some significant deformation electron density, due to improper deconvolution between these two features (Jelsch et al., 1998). The transfered multipolar refinement changes the values of the Uij thermal parameters and improves their accuracy.
When no rigid bond restrains are applied, the r.m.s. of the Hirshfeld (1976) test is 0.0042Å2 for spherical atom and 0.0040Å2 for multipolar atom models. As the Hirshfeld test was not satisfied, rigid bond restraints were applied in the refinement. The Hishfeld test may not systematically improve a lot in a multipolar atom refinement compared to a spherical atom model. This is partly because the bonding electron density shared between two atoms is generally located in the middle of the bond and the two Uij values are similarly perturbed along the bond direction when a spherical atom model is used. Also, the Uij values may be mainly affected by the errors in the diffraction data which explains the necessity here to use rigid bond restrains even in the multipolar refinement. The improvement of residual electron-density maps, of R factors and of thermal Uij parameters is limited in the case of this structure due to the predominance of errors in the diffraction data versus errors in electron-density modelling.