2-tert-Butyl-6-(cyclo­hexyl­imino­meth­yl)-4-meth­oxy­phenol

Roghayieh Jamjah; Mehdi Nekoomanesh; Tayebeh Pourjafar; Gholam Hossein Zohuri; Faramarz Afshartaromi; Behrouz Notash

doi:10.1107/S1600536811023385

. 2011 Jun 22;67(Pt 7):o1775–o1776. doi: 10.1107/S1600536811023385

2-tert-Butyl-6-(cyclohexyliminomethyl)-4-methoxyphenol

Roghayieh Jamjah ^a,^*, Mehdi Nekoomanesh ^a,^*, Tayebeh Pourjafar ^b, Gholam Hossein Zohuri ^c, Faramarz Afshartaromi ^b, Behrouz Notash ^d

PMCID: PMC3152047 PMID: 21837152

Abstract

The asymmetric unit of the title Schiff base compound, C₁₈H₂₇NO₂, contains two independent molecules in which the C=N bond lengths are 1.278 (2) and 1.280 (2) Å and the cyclohexane rings adopt chair conformations. Intramolecular O—H⋯N hydrogen bonding between hydroxy and imine groups and weak C—H⋯O hydrogen bonds help to stabilize the molecular structure.

Related literature

For general background to the synthesis and catalytic activity of the FI family of early transition metal olefin polymerization catalysts, see: Matsui & Fujita (2001 ▶); Matsui et al. (1999 ▶, 2001 ▶); Makio et al. (2002 ▶); Suzuki et al. (2006 ▶); Saito et al. (2002 ▶); Parssinen et al. (2005 ▶). For background to the synthesis of Schiff base compounds, see: Hofsløkkn & Skattebøl (1999 ▶); Wang et al. (1994 ▶); Gregson et al. (2006 ▶); Bigi et al. (2000 ▶). For the synthesis of phenoxy-imine ligands and their complexes, see: Matsukawa et al. (2001 ▶); Tohi et al. (2004 ▶); Makio et al. (2002 ▶). For related structures, see: Hiller et al. (1993 ▶); Darensbourg et al. (2005 ▶).

Experimental

Crystal data

C₁₈H₂₇NO₂
M _r = 289.41
Triclinic,
a = 10.388 (2) Å
b = 13.325 (3) Å
c = 13.766 (3) Å
α = 111.37 (3)°
β = 108.31 (3)°
γ = 92.46 (3)°
V = 1657.8 (8) Å³
Z = 4
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 120 K
0.45 × 0.45 × 0.30 mm

Data collection

Stoe IPDS II diffractometer
18474 measured reflections
8861 independent reflections
6731 reflections with I > 2σ(I)
R _int = 0.095

Refinement

R[F ² > 2σ(F ²)] = 0.059
wR(F ²) = 0.209
S = 1.09
8861 reflections
395 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.59 e Å⁻³
Δρ_min = −0.51 e Å⁻³

Data collection: X-AREA (Stoe & Cie, 2005 ▶); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811023385/xu5239sup1.cif

e-67-o1775-sup1.cif^{(29.8KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811023385/xu5239Isup2.hkl

e-67-o1775-Isup2.hkl^{(433.4KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811023385/xu5239Isup3.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
O1—H1⋯N1	0.88 (3)	1.77 (3)	2.5918 (19)	156 (3)
O3—H2⋯N2	0.90 (3)	1.73 (3)	2.5901 (19)	159 (3)
C5—H5B⋯O1	0.96	2.34	2.994 (2)	125
C6—H6B⋯O1	0.96	2.36	3.004 (2)	124
C23—H23B⋯O3	0.96	2.41	3.051 (2)	124
C24—H24B⋯O3	0.96	2.36	3.000 (2)	124

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Acknowledgments

We are grateful to the Iran Polymer and Petrochemical Institute (ippi) for financial support.

supplementary crystallographic information

Comment

In the late 1990s' Fujita group discovered and developed a new family of early transition metal catalysts [FI catalysts] (Matsui & Fujita, 2001; Matsui et al., 2001; Makio et al., 2002). These new catalysts with two phenoxy-imine chelate ligands were discovered on the basis of, ligand oriented catalyst design concept, and show high activity for olefin polymerization (Matsui et al., 1999; Suzuki et al., 2006).

FI catalysts can produce a wide variety of new polymers whose are comparable to those produced by group 4 metallocen catalysts which are unobtainable with conventional Ziegler-Natta catalysts. FI catalysts are generally comprised of transition metals (Zr, Ti, etc) (Suzuki et al., 2006) and ligand(s) with general formula of L₂MX₂ (M= Transition metal, L = ancillary ligand(s), and X= monodentate anionic ligand such as halide or amide (Matsui & Fujita, 2001; Saito et al., 2002; Parssinen et al., 2005). The basic phenoxy-imine ligand systems can be divided into two bases reactant: primary amines and salicylaldehyde derivatives.

Usually amines and some salicylaldehyde derivatives commercially are available, but some of them such as 2-hydroxy-3-tert-butyl-5-methoxy benzaldehyde and the ones with desired substituents are not commercially available and can be synthesized by straight forward synthetic methods. Formylation at the 2-position of phenols can be performed using paraformaldehyde with many established methods in high yields (typically 70–80%). Electron donating substitueants such as methoxy group at the para position of phenoxy oxygen in benzene ring enhance the rate of formulation reaction. Salicylaldehydes and primary amines are condensed into Schiff bases under standard condensation condition which can obtain with high selectivity and yields (Hofsløkkn & Skattebøl, 1999; Wang et al., 1994; Gregson et al., 2006; Bigi et al., 2000). Generally, the overall synthesis requires fewer steps and gives higher yield than those for metallocences. Rational design of the phenoxy-imine ligand and its effect on activity, thermal stability and molecular weight capabilities and molecular weight distributions that could be achieved by varying combination of R₁, R₂ and R₃ groups on the final ligand (Matsukawa et al., 2001; Tohi et al., 2004). Once again, designing the ligand frame work by addition of an electron-donating group in the R₃ position, can be impart a large electronic influence on the Zirconium and strengthening the metal-ligand interactions (Makio et al., 2002).

Herein, we report synthesis and crystal structure of new schiff base compound ((E)-2-tert-butyl-6-((cyclohexylimino)methyl)-4-methoxyphenol). The asymmetric unit of the title compound is shown in Fig. 1 and contain two molecules of schiff base compound. The bond lengths and angles are comparable to those observed for schiff base ligands (Hiller et al., 1993; Darensbourg et al., 2005). In the crystal structure of title compound, there is intramolecular bifurcated C—H···O hydrogen bondings between two methyl from t-buthyl group and hydroxy group and also intramolecular O—H···N between hydroxy and nitrogen of imine part (Table 1 & Fig. 2).

Experimental

Ligand synthesis was carried out under an atmosphere of nitrogen using oven-dried glassware. To a 100 ml flask thoroughly purged with nitrogen, 30 ml of ethanol, 1.90 g (12.0 mmol) of dried and fresh distilled cyclohexylamine and 2.08 g (10.0 mmol) of 5-methoxy 3 - t-butylsalicylaldehyde were introduced. After addition of 5 g of activated molecular sieve 3 Å, the mixture was stirred at room temperature for 12 h and then filtered. The molecular sieve 3 Å was washed with ethyl acetate (20 ml). The combined organic filtrates were concentrated in vacuum to afford a crude imine compound. Reaction solution was concentrated under reduced pressure and yellow salicylaldimine obtained. Then the product recrystallized with petroleum ether (m.p. 90°C).