(S)-1,5-Dibenzyl-3-tert-butyl­imidazol­idin-4-one

Jian-Feng Zheng; Jian-Nan Guo; Su-Yu Huang; Bo Teng; Li-Ren Jin

doi:10.1107/S1600536808018461

. 2008 Jun 25;64(Pt 7):o1330. doi: 10.1107/S1600536808018461

(S)-1,5-Dibenzyl-3-tert-butylimidazolidin-4-one

Jian-Feng Zheng ^a,^*, Jian-Nan Guo ^a, Su-Yu Huang ^a, Bo Teng ^a, Li-Ren Jin ^a

PMCID: PMC2961886 PMID: 21202954

Abstract

The title compound, C₂₁H₂₆N₂O, was obtained as an unexpected by-product when attempting to prepare (S)-2-benzyl-N-tert-butyl-1,2,3,4-tetrahydroisoquinoline-3-carboxamide from (S)-2-benzylamino-N-tert-butyl-3-phenylpropanamide and dimethoxymethane. The molecules are linked by weak C—H⋯O hydrogen bonds, generating linear chains parallel to the b axis. C—H⋯π interactions provide further stability for the crystal structure. The planes of the two phenyl rings make a dihedral angle of 84.1 (1)°. The absolute configuration was known from the starting material.

Related literature

For related literature, see: Allen et al. (1987 ▶); Pavel et al. (1993 ▶); Jin et al. 2005 ▶.

Experimental

Crystal data

C₂₁H₂₆N₂O
M _r = 322.44
Orthorhombic,
a = 9.4112 (6) Å
b = 11.4713 (7) Å
c = 17.0556 (11) Å
V = 1841.3 (2) Å³
Z = 4
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 173 (2) K
0.62 × 0.45 × 0.23 mm

Data collection

Bruker APEX CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2001 ▶) T _min = 0.957, T _max = 0.984
8034 measured reflections
2047 independent reflections
1824 reflections with I > 2σ(I)
R _int = 0.023

Refinement

R[F ² > 2σ(F ²)] = 0.042
wR(F ²) = 0.107
S = 1.00
2047 reflections
217 parameters
H-atom parameters constrained
Δρ_max = 0.34 e Å⁻³
Δρ_min = −0.18 e Å⁻³

Data collection: SMART (Bruker, 2001 ▶); cell refinement: SAINT (Bruker, 2001 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEPIII (Farrugia, 1997 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808018461/bt2725sup1.cif

e-64-o1330-sup1.cif^{(21.3KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808018461/bt2725Isup2.hkl

e-64-o1330-Isup2.hkl^{(100.7KB, 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
C6—H6A⋯O4ⁱ	0.99	2.48	3.439 (4)	164
C17—H17⋯Cgⁱⁱ	0.95	2.68	3.621 (4)	169

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Symmetry codes: (i) Inline graphic ; (ii) . Cg is the centroid of the C7–C12 phenyl ring.

Acknowledgments

The authors acknowledge the Natural Science Foundation of Fujian Province of China (No. U0650024), Xiamen Science Foundation (No.3502Z20055019) and NFFTBS (No. J0630429) for financial support. We also thank Mr Z.-B. Wei and Mr T.-B. Wen for technical assistance.

supplementary crystallographic information

Comment

In our studies on the synthesis of (S)—N-tert-butyl-tetrahydroisoquinoline- 3-carboxamide, a key intermediate for the synthesis of Nelfinavir and Saquinavir, two of the most clinically efficacious anti-AIDS drugs, we attempted to prepare (S)-2-benzyl-N-tert-butyl-1,2,3,4-tetrahydroisoquinoline- 3-carboxamide from (S)-2-(benzylamino)-N-tert-butyl-3 -phenylpropanamide and dimethoxymethane. During this experiment, the title compound, (I), was isolated unexpectedly.

The two planes of phenyl rings make a dihedral angle of 84.1 (1)° (Fig. 1). The absolute configuration (S) of the stereocentre C5 remains unchanged during the synthetic procedure. An X-ray crystal structure determination of the molecular structure of compound (I) was carried out to determine its conformation. The bond lengths are within normal ranges (Allen et al., 1987).

The packing is shown in Fig. 2. The occurrence of weak C—H···O hydrogen bond interactions leads to the formation of linear chains parallel to the b axis. The packing is further stabilized by C—H···π interactions (Fig. 2) with typical geometry (Pavel et al., 1993).

Experimental

The title compound was prepared by a method based on one described by Jin et al. (2005). To a solution of (S)-2-(benzylamino)-N-tert-butyl- 3-phenylpropanamide (11.8 g, 38.1 mmol) in dichloromethane (400 ml) was added dropwise boron trifluoride etherate (13.5 ml, 79.6 mmol) and dimethoxymethane (6.02 g, 79.1 mmol). The mixture was heated to reflux for 48 h. The reaction was quenched by addition of water (90 ml). The solution was adjusted to pH 8 with a 27% aqueous ammonia solution. The organic layer was separated, and the aqueous phase was extracted with dichloromethane. The combined organic phases were washed with brine and dried over Na₂SO₄. After filtration and evaporation of the solvents under reduced pressure, the residue was flash chromatographic purification on silica gel (ethyl acetate / petroleum ether = 1 / 4) yielded the product as a white solid. Single crystals were obtained by slow evaporation of a mixture of petroleum ether / dichloromethane solution.