tert-Butyl 3-benzyl-3-[(E)-2-benzyl­idene-3-oxocyclo­pent­yl]-2-oxoindoline-1-carboxyl­ate

Zhen Qiao; Li Liu; Dong Wang

doi:10.1107/S160053681100691X

. 2011 Mar 12;67(Pt 4):o858. doi: 10.1107/S160053681100691X

tert-Butyl 3-benzyl-3-[(E)-2-benzylidene-3-oxocyclopentyl]-2-oxoindoline-1-carboxylate

Zhen Qiao ^a, Li Liu ^a,^*, Dong Wang ^a

PMCID: PMC3099990 PMID: 21754139

Abstract

In the title compound, C₃₂H₃₁NO₄, the dihedral angles between the indoline ring and the two phenyl rings are 48.11 (9) and 66.55 (9)°. The molecular conformation is stabilized by a weak intramolecular π–π stacking interaction [centroid–centroid distance = 3.6377 (7) Å]. The crystal structure is stabilized by intermolecular C—H⋯O hydrogen bonds, which form chains along the b axis.

Related literature

For the preparation of chiral 3,3-disubstituted 2-oxindoles, see: Cozzi et al. (2009 ▶); Qiao et al. (2010 ▶); Zhou et al. (2010 ▶). For bond-length data, see: Allen et al. (1987 ▶).

Experimental

Crystal data

C₃₂H₃₁NO₄
M _r = 493.58
Orthorhombic,
a = 7.8695 (16) Å
b = 11.893 (2) Å
c = 28.346 (6) Å
V = 2652.9 (9) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 173 K
0.35 × 0.26 × 0.12 mm

Data collection

Rigaku Saturn724+ diffractometer
Absorption correction: multi-scan (CrystalClear; Rigaku, 2008 ▶) T _min = 0.525, T _max = 1.000
9151 measured reflections
2967 independent reflections
2651 reflections with I > 2σ(I)
R _int = 0.088

Refinement

R[F ² > 2σ(F ²)] = 0.055
wR(F ²) = 0.132
S = 1.05
2967 reflections
334 parameters
H-atom parameters constrained
Δρ_max = 0.20 e Å⁻³
Δρ_min = −0.23 e Å⁻³

Data collection: CrystalClear (Rigaku, 2008 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELTXL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S160053681100691X/rz2560sup1.cif

e-67-0o858-sup1.cif^{(26.1KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S160053681100691X/rz2560Isup2.hkl

e-67-0o858-Isup2.hkl^{(145.6KB, hkl)}

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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C21—H21A⋯O4ⁱ	1.00	2.37	3.295 (4)	153
C28—H28A⋯O4ⁱ	0.95	2.47	3.401 (4)	165

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Symmetry code: (i) Inline graphic .

supplementary crystallographic information

Comment

Recently, as important substructures, chiral 3,3-disubstituted 2-oxindoles have constituted a ubiquitous class of heterocycles found in numerous natural products, marketed drugs, and drug candidates. Though a handful of synthetic methods are available for creating the single quaternary carbon centers at the C-3 position with complete control, the challenge still lies primarily in the efficient construction of a vicinal chiral tertiary carbon centre. Meanwhile, the direct catalytic asymmetric substitution of alcohols represents a highly challenging and persistent problem for synthetic methodology. Because of the inert leaving ability of the hydroxyl group, the catalytic activation of alcohols is generally difficult (Cozzi et al., 2009). By using our method we can overcome the problem mentioned above (Qiao et al., 2010; Zhou et al., 2010). We report here the crystal structure of the title compound.

In title compound (Fig. 1), all bond lengths are normal (Allen et al., 1987). The dihedral angle between the indoline (C6—C13/N1) and the C15—C20 and C27—C32 phenyl rings are 48.11 (9) and 66.55 (9) °, respectively. A weak intramolecular π—π interaction is indicated by the distance of 3.6377 (7) Å between the centroids of the pyrrole ring (N1/C6/C11–13) and C15—C20 phenyl ring. In the crystal structure, weak C—H···O intermolecular hydrogen interactions link molecules into chains along the b axis (Table 1).

Experimental

To a solution of catalyst salt 9-amino-9-deoxyepiquinine (20 mol %) in the combination with TFA (40 mol %) in 1 ml DCM, 5 min s later, the Baylis-Hillman adduct 2-(hydroxy(phenyl)methyl)cyclopent-2-enone (0.2 mmol) and tert-butyl 3-benzyl-2-oxoindoline-1-carboxylate (0.2 mmol) was added. The resulting reaction mixture was heated at 30° C and stirred for 96 h till completion as judged by TLC. Then the reaction mixture was purified by column chromatography over silica gel (gradient petroleum ether/EtOAc 6:1 v/v) to afford the title compound in 32% yield. Single crystals suitable for X-ray measurements were obtained by recrystallization from acetonitrile at room temperature.