2-Methyl-4-phenyl-3,4-dihydro­quinazoline

Arto Valkonen; Erkki Kolehmainen; Anna Zakrzewska; Agnieszka Skotnicka; Ryszard Gawinecki

doi:10.1107/S1600536811009664

. 2011 Mar 19;67(Pt 4):o923–o924. doi: 10.1107/S1600536811009664

2-Methyl-4-phenyl-3,4-dihydroquinazoline

Arto Valkonen ^a,^*, Erkki Kolehmainen ^a, Anna Zakrzewska ^b, Agnieszka Skotnicka ^b, Ryszard Gawinecki ^b

PMCID: PMC3099896 PMID: 21754194

Abstract

The title compound, C₁₅H₁₄N₂, was formed during the lithiation of 2-methylquinazoline with phenyllithium followed by hydrolysis of the intermediate lithium 2-methyl-4-phenyl-4H-quinazolin-3-ide. NMR spectra as well as single-crystal X-ray structural data indicate that the reaction product to have the same structure in chloroform solution as in the crystalline state. The phenyl substituent is twisted out of the plane of the 3,4-dihydroquinazoline ring system by 86.47 (7)°. In the crystal, intermolecular N—H⋯N interactions connect the molecules into infinite chains.

Related literature

For organolithium compounds and lithiation, see: Gawinecki et al. (2006 ▶); Kolehmainen et al. (2000 ▶); Wakefield (1976 ▶); Armarego (1967 ▶). For previous characterizations of the title compound, see: Suri et al. (1993 ▶). For related structures, see: Rajnikant et al. (2002 ▶).

Experimental

Crystal data

C₁₅H₁₄N₂
M _r = 222.28
Trigonal,
a = 9.5600 (4) Å
c = 11.2569 (5) Å
V = 890.97 (7) Å³
Z = 3
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 123 K
0.35 × 0.13 × 0.12 mm

Data collection

Bruker–Nonius KappaCCD with APEXII detector diffractometer
6729 measured reflections
1468 independent reflections
1215 reflections with I > 2σ(I)
R _int = 0.068

Refinement

R[F ² > 2σ(F ²)] = 0.046
wR(F ²) = 0.095
S = 1.06
1468 reflections
155 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 0.19 e Å⁻³
Δρ_min = −0.19 e Å⁻³

Data collection: COLLECT (Bruker, 2008 ▶); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997 ▶); data reduction: DENZO-SMN; program(s) used to solve structure: SIR2004 (Burla et al., 2005 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶) and Mercury (Macrae, et al., 2008 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811009664/im2274sup1.cif

e-67-0o923-sup1.cif^{(17.3KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811009664/im2274Isup2.hkl

e-67-0o923-Isup2.hkl^{(70.9KB, 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
N3—H3⋯N1ⁱ	0.88	2.04	2.908 (3)	169

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Symmetry code: (i) Inline graphic .

Acknowledgments

Academy Professor Kari Rissanen and the Academy of Finland (project No. 212588 for KR) are gratefully acknowledged for funding. Dr Katri Laihia is thanked for characterization of the NMR spectra.

supplementary crystallographic information

Comment

Addition of phenyllithium to 2-methylquinazoline takes place exclusively at the 3,4-position (neither 2-methyl-2-phenyl-1,2-dihydroquinazoline nor 2-methyl-4-phenyl-1,4-dihydroquinazoline were detected in the reaction mixture). Susceptibility of quinazolines to undergo the nucleophilic addition to their 3,4-double bonds has been reported earlier (Suri et al., 1993). It is also known that 4-substituted 3,4-dihydroquinazolines can be generated from quinazolines when treated with organometallic compounds (Armarego, 1967). Furthermore, low susceptibility of 2-methyl group to lithiation precludes 2-methylquinazoline to be used as a starting material in syntheses of the important C_exo-substituted 2-methylquinazolines (Wakefield, 1976; Kolehmainen et al., 2000; Gawinecki et al., 2006).

In crystalline state the title compound shows the 3,4-dihydroquinazoline moiety to be planar (Fig. 1). The phenyl substituent is twisted out of plane of the moiety by 86.47 (7) °, which is rather close to the twist (79.3 (1) °) found in 2-methyl-4-phenyl-3,4-dihydroquinazolinium chloride (Rajnikant et al., 2002). Intermolecular N3—H···N1 hydrogen bonds (-y, x-y + 1, z + 1/3 direction) define the supramolecular structure and connect the molecules to infinite helical chains (Fig. 2). Unfortunately, no reliable determination of the absolute structure (or handedness of helix) is possible by X-ray crystallography.

Experimental

A solution of 2-methyl-quinazoline (10.09 g, 0.07 mol) in absolute ethyl ether (100 ml) was added dropwise with stirring to a solution of phenyllithium [obtained by a standard method starting from freshly distilled bromobenzene (15.70 g, 0.1 mol), absolute ethyl ether (0.5 L) and lithium (2.80 g, 0.4 mol)]. The reaction mixture was stirred at room temperature for additional 2 h and the reaction was quenched by addition of water (0.5 L). The organic layer was combined with the ether extracts of the water layer, dried (K₂CO₃) and evaporated to dryness. The crude solid product was recrystallized from ethanol to give white crystals (51%) melting at 168–170 °C [lit. mp 168–170 °C (Suri et al., 1993)]. ¹H NMR (CDCl₃): δ (p.p.m.) = 7.26–7.34 (m, 5H, H12—H16), 7.13 (dd, 1H, H7), 7.02 (d, 1H, H8), 6.90 (dd, 1H, H6), 6.71 (d, 1H, H5), 5.67 (s, 1H, H4), 2.02 (s, 3H, CH3). ¹³C NMR (CDCl₃): δ (p.p.m.) = 153.9 (C2), 145.3 (C11), 140.6 (C9), 128.1 (C7), 127.8 (C14), 128.7 (C13, C15), 127.3 (C12, C16), 126.7 (C5), 124.1 (C6), 123.3 (C10), 58.1 (C4), 22.5 (C17).

Suitable single crystals for X-ray diffraction were obtained by very slow evaporation of analytical sample from NMR-tube, where CDCl₃ was used as a solvent.