5-[(E)-Meth­oxy(phen­yl)methyl­idene]-1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazole

Biplab Maji; Guillaume Berionni; Herbert Mayr; Peter Mayer

doi:10.1107/S1600536812045692

. 2012 Nov 10;68(Pt 12):o3307. doi: 10.1107/S1600536812045692

5-[(E)-Methoxy(phenyl)methylidene]-1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazole

Biplab Maji ^a, Guillaume Berionni ^a, Herbert Mayr ^a, Peter Mayer ^a,^*

PMCID: PMC3588847 PMID: 23468812

Abstract

In the title compound, C₂₈H₂₃N₃O, the 1,2,4-triazole ring deviates slightly from planarity adopting a ^N3 T _C2 conformation which is distorted towards an E _C2 conformation. The plane around the ethylene unit makes a dihedral angle of 17.32 (11)° with the mean plane [r.m.s. deviation = 0.036 (1) Å] of the 1,2,4-triazole fragment. The dihedral angles between the four phenyl rings and the 1,2,4-triazole ring are 31.01 (10), 49.01 (8), 78.55 (6) and 41.51 (9)°. In the crystal, molecules are linked along [100] by weak C—H⋯O hydrogen bonds.

Related literature

For chemical background, see: Arduengo et al. (1991 ▶); Enders et al. (2007 ▶); Biju et al. (2011 ▶); Breslow (1958 ▶). For puckering analysis, see: Cremer & Pople (1975 ▶). For a related structure, see: Nair et al. (2008 ▶).

Experimental

Crystal data

C₂₈H₂₃N₃O
M _r = 417.49
Monoclinic,
a = 5.8831 (2) Å
b = 10.5560 (2) Å
c = 35.0548 (8) Å
β = 93.749 (1)°
V = 2172.31 (10) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 200 K
0.35 × 0.09 × 0.04 mm

Data collection

Nonius KappaCCD diffractometer
12170 measured reflections
3797 independent reflections
2601 reflections with I > 2σ(I)
R _int = 0.058

Refinement

R[F ² > 2σ(F ²)] = 0.045
wR(F ²) = 0.116
S = 1.02
3797 reflections
290 parameters
H-atom parameters constrained
Δρ_max = 0.14 e Å⁻³
Δρ_min = −0.17 e Å⁻³

Data collection: COLLECT (Nonius, 1998) ▶; cell refinement: SCALEPACK (Otwinowski & Minor, 1997 ▶); data reduction: DENZO (Otwinowski & Minor, 1997 ▶) and SCALEPACK; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶); software used to prepare material for publication: PLATON (Spek, 2009 ▶).

Supplementary Material

Click here for additional data file.^{(29.6KB, cif)}

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812045692/lx2259sup1.cif

e-68-o3307-sup1.cif^{(29.6KB, cif)}

Click here for additional data file.^{(186.2KB, hkl)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812045692/lx2259Isup2.hkl

e-68-o3307-Isup2.hkl^{(186.2KB, hkl)}

Click here for additional data file.^{(8.5KB, cml)}

Supplementary material file. DOI: 10.1107/S1600536812045692/lx2259Isup3.cml

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
C20—H20⋯O1ⁱ	0.95	2.43	3.162 (3)	134

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Symmetry code: (i) Inline graphic .

Acknowledgments

The authors thank Professor Peter Klüfers for generous allocation of diffractometer time.

supplementary crystallographic information

Comment

Umpolung reactions of aldehydes catalyzed by N-heterocyclic carbenes [Arduengo et al. (1991)] belong to the most important organocatalytic CC bond-forming reactions [Enders et al. (2007), Biju et al. (2011)]. An acyl anion equivalent, the so called Breslow intermediate [Breslow (1958)] was proposed to be the key intermediate of these transformations.

To understand the structure of these intermediates, we report herein the crystal structure of the title compound.

In the title molecule (Fig. 1), the 1,2,4-triazole fragment is nearly planar, with a mean deviation of 0.036 (1) Å from the least-squares plane defined by the five constituent atoms.

The asymmetric unit contains one molecule of the title compound which is shown in Figure 1.

Puckering analysis [Cremer et al. (1975)] reveals that the 4,5-dihydro-1H-1,2,4-triazole ring adopts a ^N3T_C2 conformation which is distorted towards a E_C2 conformation. In a related structure [Nair et al. (2008)] of a compound which is different from the title compound only through the substituent connected by a double bond with the 4,5-dihydro-1H-1,2,4-triazole ring, the latter ring is planar and not puckered. The methoxy(phenyl)methylene group is bound to the 4,5-dihydro-1H-1,2,4-triazole ring in a distance of 1.358 (3) Å which indicates a double bond. However, the plane of the heterocycle and the plane around the methylene atom are not coplanar but enclose a dihedral angle of 17.32 (11)°. In the related structure, the corresponding dihedral angle is 42.5 (4)°. The plane of the phenyl ring bound to the methylene atom is not coplanar with the plane around the methylene atom as well (dihedral angle 34.14 (10)°). The dihedral angles between the four phenyl rings and the mean plane of the 1,2,4-triazole ring are 31.01 (10)° [the C3-C8 phenyl ring], 49.01 (8)° [the C9-C14 phenyl ring], 78.55 (6)° [the C15-C20 phenyl ring] and 41.51 (9)° [the C22-C27 phenyl ring]. In the crystal packing, molecules are connected by weak C–H···O hydrogen bonds (Table 1).

Experimental

To an oven dried Schlenk-flask charged with NaH (48 mg, 2.0 mmol), tBuOK (11 mg, 98 mol), and 5-(methoxy(phenyl)methyl)-1,3,4-triphenyl-4H-1,2,4-triazolium chloride (454 mg, 1.00 mmol) was added dry THF (15 ml) under nitrogen and the reaction mixture was allowed to stir for 4 h in the dark. The solvent was then removed under vacuum, and the residue was suspended in dry toluene (20 ml) and filtered through a celite pad under nitrogen. Then the solvent was evaporated to give 296 mg (0.709 mmol, 71%) of the title compound as 10:1 mixture of E:Z isomers. Crystals suitable for X-ray crystallography were grown by cooling down a saturated acetonitrile solution at -30 °C under argon for 48 h.