organic compounds
3-Chloro-4-dimethylamino-5-[(1R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy]furan-2(5H)-one
aResearch Center of Chemistry & Materials, Zhanjiang Normal College, People's Republic of China, bDevelopment Center for New Materials Engineering &, Technology in Universities of Guangdong, People's Republic of China, cChemistry Science & Technology School, Zhanjiang Normal College, Zhanjiang 524048, People's Republic of China, dSchool of Chemistry and Environment, South China Normal University, Guangzhou 510006, People's Republic of China, and eResearch Institute of Tsinghua University in Shenzhen, Shenzhen 518055, People's Republic of China
*Correspondence e-mail: sxmfn@163.com
The title compound, C16H26ClNO3 contains one almost planar furanone ring [maximum deviation of 0.021 (2) Å for the O atom] with a stereogenic center (S) and one cyclohexane ring which displays a chair conformation and has three stereogenic centers [S at the C atom bearing the isopropyl group, R at the C atom attached to the O atom and R at the C atom bearing the methyl group].
Related literature
For natural products containing a 2(5H)-furanone subunit, see: Ming et al. (2002). For biologically active 2(5H)-furanones, see: Bailly et al. (2008). For the synthesis of 2(5H)-furanones with substituents in positions 3 and 4, see: Van Oeveren et al. (1994); For related structures, see: Chen et al. (1995); Martín & Mateo (1995); Gawronski et al. (1997). For the use of benzimidazoles in organic synthesis, see: Mao et al. (2010). For standard bond lengths, see: Allen et al. (1987); Orpen et al. (1989). For the structures of heterosubstituted 2(5H)-furanones, see: Gawronski et al. (1997). For the synthesis and structure of optically pure 5-(l-menthyloxy)-3,4-dichloro-2(5H)-furanone, see: Chen & Geng (1993). For a description of the Cambridge Structural Database, see: Allen (2002).
Experimental
Crystal data
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Data collection: APEX2 (Bruker, 2004); cell SAINT (Bruker, 2004); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97.
Supporting information
10.1107/S1600536811015583/si2350sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536811015583/si2350Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536811015583/si2350Isup3.cml
The optically pure precursor 3,4-dichloro-5-(S)-(l-menthyloxy)-2(5H)-furanone was prepared according to the literature procedure (Chen & Geng, 1993).
The title compond, 3-chloro-4-N,N-dimethyl-5-(S)-(l-menthyloxy)-2(5H)-furanone, was prepared by reaction of 3,4-dichloro-5-(S)-(l-menthyloxy)-2(5H)-furanone (3 mmol) and DMF (1 ml) at 80 °C, catalyzed by sodium ethanol (3 mmol) under N2 atmosphere. After stirring for 24 h, ice water was added to the mixture and then extracted by dichloromethane. The solvent was evaporated in vacuo and the precipitate was purified by silica gel
with gradient mixture of petroleum ether and ethyl acetate (Yield 21.3%). Single crystals of the title compound were obtained by slow evaporation of a solution in acetonitrile at room temperature.Data for (I): m.p.161.0–163.0 °C; IR (KBr) ν: 2953.73, 748.40, 1630.61 cm-1; 1H NMR (400 MHz, CDCl3, TMS): 0.762 (3H, d, J = 6.8 Hz, CH3-7), 0.820–0.858 (1H, m, CH-8), 0.909 (3H, s, CH3-9), 0.926 (3H, s, CH3-10), 0.956–1.170 (2H, m, CH2-6), 1.290–1.427 (2H, m, CH-2, CH-5), 1.633–1.695 (2H, m, CH2-1), 2.171–2.211 (2H, m, CH2-4), 3.186 (6H, s, CH3-11, CH3-12), 3.532–3.845 (1H, ddd, J = 4.4 Hz, 4.4 Hz, 4.4 Hz, CH-3), 5.757 (1H, s, CH-16).
All H atoms were positioned in calculated positions (C—H = 0.96 Å or 0.97 Å or 0.98 Å) and were refined using a riding model, with Uiso(H) = 1.2 Ueq(C) for methylene or methine H atoms and Uiso(H) = 1.5 Ueq(C) for methyl H atoms.
Data collection: APEX2 (Bruker, 2004); cell
SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).Fig. 1. The molecular structure of the title compound. Displacement ellipsoids drawn at the 30% probability level, hydrogen atoms have been omitted for clarity. |
C16H26ClNO3 | F(000) = 680 |
Mr = 315.83 | Dx = 1.191 Mg m−3 |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 3099 reflections |
a = 7.5438 (5) Å | θ = 2.8–20.5° |
b = 8.1631 (5) Å | µ = 0.23 mm−1 |
c = 28.5953 (17) Å | T = 296 K |
V = 1760.92 (19) Å3 | Block, colourless |
Z = 4 | 0.23 × 0.22 × 0.19 mm |
Bruker APEXII area-detector diffractometer | 2922 independent reflections |
Radiation source: fine-focus sealed tube | 1951 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.049 |
ϕ and ω scans | θmax = 25.2°, θmin = 1.4° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −8→7 |
Tmin = 0.950, Tmax = 0.958 | k = −9→6 |
9112 measured reflections | l = −23→34 |
Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
Least-squares matrix: full | H-atom parameters constrained |
R[F2 > 2σ(F2)] = 0.047 | w = 1/[σ2(Fo2) + (0.055P)2] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.117 | (Δ/σ)max < 0.001 |
S = 1.02 | Δρmax = 0.15 e Å−3 |
2922 reflections | Δρmin = −0.14 e Å−3 |
196 parameters | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.016 (2) |
Primary atom site location: structure-invariant direct methods | Absolute structure: Flack (1983), 1066 Friedel pairs |
Secondary atom site location: difference Fourier map | Absolute structure parameter: −0.05 (9) |
C16H26ClNO3 | V = 1760.92 (19) Å3 |
Mr = 315.83 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 7.5438 (5) Å | µ = 0.23 mm−1 |
b = 8.1631 (5) Å | T = 296 K |
c = 28.5953 (17) Å | 0.23 × 0.22 × 0.19 mm |
Bruker APEXII area-detector diffractometer | 2922 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 1951 reflections with I > 2σ(I) |
Tmin = 0.950, Tmax = 0.958 | Rint = 0.049 |
9112 measured reflections |
R[F2 > 2σ(F2)] = 0.047 | H-atom parameters constrained |
wR(F2) = 0.117 | Δρmax = 0.15 e Å−3 |
S = 1.02 | Δρmin = −0.14 e Å−3 |
2922 reflections | Absolute structure: Flack (1983), 1066 Friedel pairs |
196 parameters | Absolute structure parameter: −0.05 (9) |
0 restraints |
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 | 0.4580 (5) | 0.8674 (4) | 0.45480 (10) | 0.0785 (11) | |
H1A | 0.3934 | 0.7827 | 0.4714 | 0.094* | |
H1B | 0.5740 | 0.8773 | 0.4691 | 0.094* | |
C2 | 0.4806 (4) | 0.8152 (4) | 0.40327 (9) | 0.0628 (9) | |
H2 | 0.5491 | 0.9020 | 0.3880 | 0.075* | |
C3 | 0.2995 (4) | 0.8133 (3) | 0.37990 (9) | 0.0525 (8) | |
H3 | 0.2272 | 0.7270 | 0.3942 | 0.063* | |
C4 | 0.2051 (5) | 0.9754 (3) | 0.38525 (9) | 0.0701 (10) | |
H4A | 0.0895 | 0.9685 | 0.3705 | 0.084* | |
H4B | 0.2724 | 1.0599 | 0.3693 | 0.084* | |
C5 | 0.1815 (6) | 1.0237 (4) | 0.43669 (11) | 0.0804 (11) | |
H5 | 0.1112 | 0.9379 | 0.4519 | 0.096* | |
C6 | 0.3610 (7) | 1.0271 (4) | 0.45991 (11) | 0.0893 (12) | |
H6A | 0.4316 | 1.1140 | 0.4462 | 0.107* | |
H6B | 0.3462 | 1.0514 | 0.4929 | 0.107* | |
C7 | 0.0799 (7) | 1.1841 (5) | 0.44127 (12) | 0.1207 (16) | |
H7A | 0.0713 | 1.2137 | 0.4737 | 0.181* | |
H7B | −0.0369 | 1.1710 | 0.4285 | 0.181* | |
H7C | 0.1413 | 1.2688 | 0.4245 | 0.181* | |
C8 | 0.5869 (5) | 0.6562 (4) | 0.39706 (11) | 0.0718 (10) | |
H8 | 0.5775 | 0.6257 | 0.3640 | 0.086* | |
C9 | 0.5161 (5) | 0.5122 (4) | 0.42518 (12) | 0.0989 (14) | |
H9A | 0.5293 | 0.5345 | 0.4580 | 0.148* | |
H9B | 0.5814 | 0.4151 | 0.4173 | 0.148* | |
H9C | 0.3930 | 0.4960 | 0.4181 | 0.148* | |
C10 | 0.7855 (5) | 0.6823 (6) | 0.40726 (13) | 0.1098 (14) | |
H10A | 0.8276 | 0.7752 | 0.3899 | 0.165* | |
H10B | 0.8507 | 0.5865 | 0.3981 | 0.165* | |
H10C | 0.8019 | 0.7016 | 0.4401 | 0.165* | |
C11 | 0.2476 (5) | 0.4116 (4) | 0.31317 (11) | 0.0793 (11) | |
H11A | 0.3620 | 0.3966 | 0.3272 | 0.119* | |
H11B | 0.1923 | 0.3069 | 0.3087 | 0.119* | |
H11C | 0.1751 | 0.4777 | 0.3333 | 0.119* | |
C12 | 0.3298 (6) | 0.3891 (4) | 0.23027 (11) | 0.0928 (12) | |
H12A | 0.2355 | 0.3726 | 0.2082 | 0.139* | |
H12B | 0.3670 | 0.2853 | 0.2426 | 0.139* | |
H12C | 0.4280 | 0.4411 | 0.2149 | 0.139* | |
C13 | 0.2303 (4) | 0.6503 (3) | 0.26159 (9) | 0.0495 (7) | |
C14 | 0.2256 (4) | 0.7458 (3) | 0.22286 (9) | 0.0530 (8) | |
C15 | 0.1758 (4) | 0.9092 (4) | 0.23489 (11) | 0.0588 (8) | |
C16 | 0.1844 (4) | 0.7605 (3) | 0.30258 (10) | 0.0529 (8) | |
H16 | 0.0818 | 0.7180 | 0.3198 | 0.063* | |
Cl1 | 0.26385 (14) | 0.70164 (12) | 0.16516 (3) | 0.0940 (4) | |
N1 | 0.2678 (3) | 0.4928 (3) | 0.26825 (8) | 0.0609 (7) | |
O1 | 0.3317 (3) | 0.7719 (2) | 0.33142 (6) | 0.0524 (5) | |
O2 | 0.1456 (3) | 0.9169 (2) | 0.28218 (6) | 0.0627 (6) | |
O3 | 0.1584 (3) | 1.0295 (3) | 0.21086 (7) | 0.0817 (7) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.098 (3) | 0.095 (3) | 0.0424 (19) | −0.022 (2) | −0.0045 (19) | −0.0019 (18) |
C2 | 0.075 (3) | 0.077 (2) | 0.0371 (18) | −0.022 (2) | −0.0020 (17) | 0.0055 (15) |
C3 | 0.062 (2) | 0.0594 (16) | 0.0362 (16) | −0.0128 (16) | 0.0064 (15) | −0.0012 (12) |
C4 | 0.095 (3) | 0.0667 (18) | 0.0485 (18) | −0.0030 (19) | 0.0067 (19) | −0.0073 (14) |
C5 | 0.116 (4) | 0.075 (2) | 0.050 (2) | 0.001 (2) | 0.010 (2) | −0.0140 (16) |
C6 | 0.137 (4) | 0.086 (2) | 0.045 (2) | −0.017 (3) | 0.002 (2) | −0.0115 (18) |
C7 | 0.174 (4) | 0.106 (3) | 0.082 (3) | 0.036 (3) | 0.010 (3) | −0.038 (2) |
C8 | 0.070 (3) | 0.093 (3) | 0.053 (2) | −0.005 (2) | −0.0094 (19) | 0.0014 (18) |
C9 | 0.118 (4) | 0.096 (3) | 0.083 (3) | 0.003 (3) | −0.010 (3) | 0.025 (2) |
C10 | 0.069 (3) | 0.178 (4) | 0.083 (3) | −0.002 (3) | −0.016 (2) | 0.003 (3) |
C11 | 0.090 (3) | 0.0654 (17) | 0.082 (2) | 0.004 (2) | −0.013 (2) | 0.0145 (17) |
C12 | 0.101 (3) | 0.078 (2) | 0.099 (3) | 0.025 (2) | −0.005 (2) | −0.029 (2) |
C13 | 0.047 (2) | 0.0554 (16) | 0.0464 (16) | −0.0003 (15) | −0.0049 (16) | −0.0037 (14) |
C14 | 0.052 (2) | 0.0640 (17) | 0.0426 (18) | −0.0003 (15) | −0.0025 (15) | −0.0071 (14) |
C15 | 0.052 (2) | 0.0674 (19) | 0.057 (2) | −0.0010 (17) | −0.0063 (18) | 0.0047 (17) |
C16 | 0.057 (2) | 0.0535 (16) | 0.0482 (17) | −0.0012 (15) | −0.0009 (17) | −0.0027 (14) |
Cl1 | 0.1203 (10) | 0.1131 (7) | 0.0485 (5) | 0.0028 (6) | 0.0062 (5) | −0.0091 (4) |
N1 | 0.065 (2) | 0.0527 (13) | 0.0646 (16) | 0.0081 (13) | −0.0033 (15) | −0.0077 (12) |
O1 | 0.0491 (14) | 0.0721 (11) | 0.0360 (10) | −0.0039 (10) | −0.0030 (10) | −0.0042 (9) |
O2 | 0.0772 (17) | 0.0524 (11) | 0.0586 (14) | 0.0124 (11) | −0.0053 (12) | −0.0035 (10) |
O3 | 0.0903 (19) | 0.0725 (13) | 0.0823 (16) | 0.0021 (13) | −0.0102 (15) | 0.0247 (12) |
C1—C6 | 1.502 (5) | C9—H9A | 0.9600 |
C1—C2 | 1.544 (4) | C9—H9B | 0.9600 |
C1—H1A | 0.9700 | C9—H9C | 0.9600 |
C1—H1B | 0.9700 | C10—H10A | 0.9600 |
C2—C3 | 1.521 (4) | C10—H10B | 0.9600 |
C2—C8 | 1.536 (5) | C10—H10C | 0.9600 |
C2—H2 | 0.9800 | C11—N1 | 1.453 (3) |
C3—O1 | 1.447 (3) | C11—H11A | 0.9600 |
C3—C4 | 1.511 (4) | C11—H11B | 0.9600 |
C3—H3 | 0.9800 | C11—H11C | 0.9600 |
C4—C5 | 1.533 (4) | C12—N1 | 1.454 (4) |
C4—H4A | 0.9700 | C12—H12A | 0.9600 |
C4—H4B | 0.9700 | C12—H12B | 0.9600 |
C5—C6 | 1.509 (6) | C12—H12C | 0.9600 |
C5—C7 | 1.523 (5) | C13—N1 | 1.331 (3) |
C5—H5 | 0.9800 | C13—C14 | 1.354 (3) |
C6—H6A | 0.9700 | C13—C16 | 1.518 (4) |
C6—H6B | 0.9700 | C14—C15 | 1.428 (4) |
C7—H7A | 0.9600 | C14—Cl1 | 1.713 (3) |
C7—H7B | 0.9600 | C15—O3 | 1.205 (3) |
C7—H7C | 0.9600 | C15—O2 | 1.373 (3) |
C8—C9 | 1.521 (4) | C16—O1 | 1.387 (3) |
C8—C10 | 1.541 (5) | C16—O2 | 1.434 (3) |
C8—H8 | 0.9800 | C16—H16 | 0.9800 |
C6—C1—C2 | 112.7 (3) | C2—C8—H8 | 106.8 |
C6—C1—H1A | 109.0 | C10—C8—H8 | 106.8 |
C2—C1—H1A | 109.0 | C8—C9—H9A | 109.5 |
C6—C1—H1B | 109.0 | C8—C9—H9B | 109.5 |
C2—C1—H1B | 109.0 | H9A—C9—H9B | 109.5 |
H1A—C1—H1B | 107.8 | C8—C9—H9C | 109.5 |
C3—C2—C8 | 114.2 (3) | H9A—C9—H9C | 109.5 |
C3—C2—C1 | 108.8 (3) | H9B—C9—H9C | 109.5 |
C8—C2—C1 | 113.7 (3) | C8—C10—H10A | 109.5 |
C3—C2—H2 | 106.5 | C8—C10—H10B | 109.5 |
C8—C2—H2 | 106.5 | H10A—C10—H10B | 109.5 |
C1—C2—H2 | 106.5 | C8—C10—H10C | 109.5 |
O1—C3—C4 | 112.3 (2) | H10A—C10—H10C | 109.5 |
O1—C3—C2 | 105.8 (2) | H10B—C10—H10C | 109.5 |
C4—C3—C2 | 111.7 (3) | N1—C11—H11A | 109.5 |
O1—C3—H3 | 109.0 | N1—C11—H11B | 109.5 |
C4—C3—H3 | 109.0 | H11A—C11—H11B | 109.5 |
C2—C3—H3 | 109.0 | N1—C11—H11C | 109.5 |
C3—C4—C5 | 112.1 (2) | H11A—C11—H11C | 109.5 |
C3—C4—H4A | 109.2 | H11B—C11—H11C | 109.5 |
C5—C4—H4A | 109.2 | N1—C12—H12A | 109.5 |
C3—C4—H4B | 109.2 | N1—C12—H12B | 109.5 |
C5—C4—H4B | 109.2 | H12A—C12—H12B | 109.5 |
H4A—C4—H4B | 107.9 | N1—C12—H12C | 109.5 |
C6—C5—C7 | 113.5 (3) | H12A—C12—H12C | 109.5 |
C6—C5—C4 | 108.8 (3) | H12B—C12—H12C | 109.5 |
C7—C5—C4 | 111.2 (3) | N1—C13—C14 | 132.7 (3) |
C6—C5—H5 | 107.7 | N1—C13—C16 | 120.7 (2) |
C7—C5—H5 | 107.7 | C14—C13—C16 | 106.5 (2) |
C4—C5—H5 | 107.7 | C13—C14—C15 | 110.3 (2) |
C1—C6—C5 | 112.2 (3) | C13—C14—Cl1 | 131.5 (2) |
C1—C6—H6A | 109.2 | C15—C14—Cl1 | 118.2 (2) |
C5—C6—H6A | 109.2 | O3—C15—O2 | 120.4 (3) |
C1—C6—H6B | 109.2 | O3—C15—C14 | 130.7 (3) |
C5—C6—H6B | 109.2 | O2—C15—C14 | 108.9 (2) |
H6A—C6—H6B | 107.9 | O1—C16—O2 | 110.2 (2) |
C5—C7—H7A | 109.5 | O1—C16—C13 | 108.4 (2) |
C5—C7—H7B | 109.5 | O2—C16—C13 | 105.1 (2) |
H7A—C7—H7B | 109.5 | O1—C16—H16 | 111.0 |
C5—C7—H7C | 109.5 | O2—C16—H16 | 111.0 |
H7A—C7—H7C | 109.5 | C13—C16—H16 | 111.0 |
H7B—C7—H7C | 109.5 | C13—N1—C11 | 123.0 (2) |
C9—C8—C2 | 114.1 (3) | C13—N1—C12 | 121.6 (3) |
C9—C8—C10 | 110.4 (3) | C11—N1—C12 | 115.4 (2) |
C2—C8—C10 | 111.6 (3) | C16—O1—C3 | 116.8 (2) |
C9—C8—H8 | 106.8 | C15—O2—C16 | 109.0 (2) |
Experimental details
Crystal data | |
Chemical formula | C16H26ClNO3 |
Mr | 315.83 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 296 |
a, b, c (Å) | 7.5438 (5), 8.1631 (5), 28.5953 (17) |
V (Å3) | 1760.92 (19) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.23 |
Crystal size (mm) | 0.23 × 0.22 × 0.19 |
Data collection | |
Diffractometer | Bruker APEXII area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.950, 0.958 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 9112, 2922, 1951 |
Rint | 0.049 |
(sin θ/λ)max (Å−1) | 0.599 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.047, 0.117, 1.02 |
No. of reflections | 2922 |
No. of parameters | 196 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.15, −0.14 |
Absolute structure | Flack (1983), 1066 Friedel pairs |
Absolute structure parameter | −0.05 (9) |
Computer programs: APEX2 (Bruker, 2004), SAINT (Bruker, 2004), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).
Acknowledgements
The work was supported by the National Natural Science Foundation of China (grant No. 20772035) and the Natural Science Foundation of Guangdong Province, China (grant No. 5300082).
References
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2(5H)-Furanones, also known as crotonolactones or butenolides, have attracted increasing attention of many organic chemists due to their presence as a subunit in many natural products (Ming et al., 2002). This core unit is the key structure to induce a variety of biological phenomena like antifungal, anti-inflamatory, antibacterial, and HIV-1 anti-integrase (Bailly et al., 2008). In recent years, chiral 2(5H)-furanones with substituents in positions 3 and 4 have been synthesized in several laboratories (Van Oeveren et al., 1994) and their crystal structures have been reported (Chen et al., 1995; Martín & Mateo, 1995; Gawronski et al., 1997).
Meanwhile, benzimidazoles were widely used in various areas, especially serving as key intermediate in organic synthesis (Mao et al., 2010). In our initial study, we focused on the Michael addition-elimination reaction of 3,4-dichloro-5-(S)-(l-menthyloxy)-2(5H)-furanone and nucleophilic reagent imidazole. On the basis of the experiment, no target molecule was obtained, but the unexpected product, 3-chloro-4-N,N-dimethyl-5-(S)-(l-menthyloxy)-2(5H)-furanone that came from reaction of 3,4-dichloro-5-(S)-(l-menthyloxy)-2(5H)-furanone and the solvent N,N-dimethylformamide was given.
In the title compound (Fig. 1), the cyclohexane ring displays a chair conformation and has three stereogenic centers (C2(S), C3(R), C5(R)), and the planar core structure subunit, the furanone ring exhibits a C16(S) center with a maximum deviation of 0.021 (2) Å of O2 from the mean plane of the five atoms defining the plane, r.m.s deviation is 0.0158 Å.
Cl substitution at C14 causes significant torsion around the C13—N1 bond. The C14—C13—N1—C12 torsion angle amounts to 5.2 (5)°, this indicates a significant twist around the C13—N1 bond resulting from Cl substitution at C14.
At the same time, N1 is only 0.034 (5) Å from the furanone ring plane. This is one manifestation of the extensive conjugation of the N1 lone pair, the C13═C14 double bond and the C15 carbonyl bond. The geometrical consequence is a shortening of the N1—C13 bond to an value of 1.331 (3) Å, which might be compared with the average value of 1.355 (14) Å for the C—N bond in C═C—N—(C)2 system (Orpen et al., 1989; Gawronski et al., 1997). The shortening of the N1—C13 bond is accompanied by the lengthening of the formally C13═C14 double bond to an value of 1.354 (3) Å, as compared with the value of 1.323 (13) Å quoted for cyclopentene and with 1.340 (13) Å in conjugated systems (Orpen et al., 1989).
And the most striking geometrical change due to conjugation is found in the furanone ring. Comparison with the non-fused furanones which contain oxygen function at C(4) (22 observations subtracted from the Cambridge Structural Database 14) (Allen, 2002) reveals significant shortening of the formally single C(sp2)—C(sp2) bond to an value of 1.428 (4) Å and simultaneous lengthening of the C(carbonyl)—O bond to an value of 1.373 (3) Å. In non-fused furanones the two bonds have the mean values of 1.466 (26) Å and 1.362 (16) Å, respectively (Allen et al., 1987; Gawronski et al., 1997). This might indicate that the essential part of the electron delocalization is concentrated in the N1, C13, C14, C15 and O3 region, and takes place at the expense of delocalization within the ester function.