Crystallography Reports, Vol. 45, No. 4, 2000, pp. 611–614. From Kristallografiya, Vol. 45, No. 4, 2000, pp. 669–672.Original English Text Copyright © 2000 by Rajnikant, Gupta, Attar Singh.

STRUCTURE OF ORGANIC COMPOUNDS

X-ray Structure Analysis of 5N-Ethyl-8-Carboxy-9-Oxo-11-Methyl-Pyrido[2,1-b]quinazoline1

Rajnikant,2 V. R. Gupta, and Attar SinghX-ray Crystallography Laboratory, Department of Physics, University of Jammu, Jammu Tawi, 180006 India

Received March 4, 1999; in final form, April 26, 1999

Abstract—The crystal structure of 5N-ethyl-8-carboxy-9-oxo-11-methyl-pyrido[2,1-b]quinazoline(C16H16N2O3) has been determined by X-ray diffraction analysis. The compound crystallizes in the monocliniccrystal system (space group P21/c) with the unit cell parameters a = 9.775(1) Å, b = 15.868(1) Å, c =9.799(1) Å, β = 113.50(1)°, Z = 4. The benzene ring is planar, the pyrimidine ring exists in 11β-sofa conforma-tion, and the pyridone ring deviates slightly from planarity. The crystal packing exhibits intra- and intermole-cular interactions of the O–H⋅⋅⋅O, C–H⋅⋅⋅O, and C–H⋅⋅⋅N types. © 2000 MAIK “Nauka/Interperiodica”.

12 5N-ethyl-8-carboxy-9-oxo-11-methyl-pyrido[2,1-b]quinazoline has been prepared by refluxing 2,4-dim-ethyl-2,3-dihydroquinazoline and diethyl ethoxy meth-ylene malonate [1]. The present work has been under-taken as a part of our systematic research on thecrystallographic analysis of several important organicmolecules [2–12].

EXPERIMENTAL

Rectangular shaped crystals of 5N-ethyl-8-carboxy-9-oxo-11-methyl-pyrido[2,1-b]quinazoline weregrown from chloroform at room temperature. Three-dimensional intensity data were collected on an Enraf–

1 This article was submitted by the authors in English.2 Author for correspondence; e-mail: rajni_kant_verma@hot-

mail.com

1063-7745/00/4504- $20.00 © 20611

Nonius CAD4 single-crystal X-ray diffractometer atthe Indian Institute of Technology (Chennai). The unitcell parameters were refined by the least-squares proce-dure. The data were corrected for Lorentz and polariza-tion factors, but no absorption or extinction correctionswere made.

The crystal structure has been determined by directmethods using the SHELXS86 software package [13].The full-matrix least-squares refinement of the struc-ture has been carried out by using the SHELXL93 soft-ware package [14]. All the H atoms were located fromthe difference Fourier map. Three cycles of refinementof the positional and anisotropic thermal parameters forthe non-hydrogen atoms and the positional and isotro-pic thermal parameters for the hydrogen atoms yieldedR = 0.048. The crystallographic data are summarized inTable 1.

Table 1. Crystal data and experimental details

Crystal habit Light yellow rectangular Absorption coefficient, mm–1 0.777

Chemical formula C16H16N2O3 F(000) 600

Molecular weight 284.3 Crystal size, mm 0.40 × 0.25 × 0.20

Crystal system Monoclinic Refinement of unit cell 25 reflections, 26° ≤ 2θ ≤ 42°Unit cell parameters θ range for entire data collection 1° ≤ θ ≤ 70°a, Å 9.775(1) No. of measured reflections 2852

b, Å 15.868(1) No. of unique reflections 2580

c, Å 9.799(1) No. of observed reflections [F > 4σ(F)] 2578

β, deg 113.50(1) No. of parameters refined 255

Unit cell volume, Å3 1393.9 Final R-factor 0.048

Density (calculated), g/cm3 1.355 wR 0.143

No. of molecules per unit cell 4 Weighting scheme 1/[σ2(Feq)2 + 0.0774P2 + 0.35P]

Space group P21/c Final residual electron density e ⋅ Å–3 –0.21–+0.22

Wavelength λ CuKα Maximum ratio –0.105[xH(2)]

000 MAIK “Nauka/Interperiodica”

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RAJNIKANT

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.

Table 2. Atomic coordinates and equivalent isotropic (isotropic for hydrogen atoms) thermal parameters (Å2)

Atom x y z Ueq/ Atom x y z Ueq/

C(1) 0.5204(2) 0.7712(1) –0.0278(2) 0.057(1) C(16) 0.4116(3) 0.4466(1) –0.2562(3) 0.062(1)

O(1) 1.1543(2) 0.4009(1) 0.3496(2) 0.079(1) C(17) 1.1039(2) 0.4718(1) 0.3288(2) 0.055(1)

C(2) 0.3694(3) 0.7822(1) –0.1095(3) 0.068(1) C(18) 0.8398(2) 0.7315(1) –0.0643(2) 0.053(1)

O(2) 1.1695(2) 0.5331(1) 0.4262(2) 0.074(1) H(1) 0.577(2) 0.812(1) 0.050(2) 0.06(1)

C(3) 0.2914(2) 0.7235(1) –0.2150(3) 0.065(1) H(2) 0.325(3) 0.832(2) –0.089(3) 0.09(1)

O(3) 0.9898(1) 0.6410(1) 0.2639(1) 0.057(1) H(3) 0.189(3) 0.731(2) –0.276(3) 0.09(1)

C(4) 0.3606(2) 0.6521(1) –0.2393(2) 0.055(1) H(4) 0.308(2) 0.611(1) –0.308(2) 0.06(1)

N(5) 0.5906(2) 0.5678(1) –0.1687(1) 0.042(1) H(6) 0.715(2) 0.418(1) –0.099(2) 0.06(1)

C(6) 0.7689(2) 0.4597(1) –0.0346(2) 0.046(1) H(7) 0.925(2) 0.379(1) 0.105(2) 0.06(1)

C(7) 0.8928(2) 0.4384(1) 0.0903(2) 0.046(1) H(11) 0.796(2) 0.716(1) 0.122(2) 0.05(1)

C(8) 0.9703(2) 0.4967(1) 0.1974(2) 0.043(1) H(151) 0.586(2) 0.477(1) –0.315(2) 0.06(1)

C(9) 0.9236(2) 0.5822(1) 0.1770(2) 0.042(1) H(152) 0.454(2) 0.544(1) –0.380(2) 0.05(1)

N(10) 0.7968(1) 0.6018(1) 0.0500(1) 0.038(1) H(161) 0.463(3) 0.410(1) –0.177(3) 0.07(1)

C(11) 0.7588(2) 0.6927(1) 0.0239(2) 0.042(1) H(162) 0.335(3) 0.477(2) –0.220(3) 0.11(1)

C(12) 0.5929(2) 0.7013(1) –0.0520(2) 0.043(1) H(163) 0.361(3) 0.409(2) –0.335(4) 0.10(1)

C(13) 0.5131(2) 0.6409(1) –0.1554(2) 0.043(1) H(17) 1.113(3) 0.586(2) 0.381(3) 0.10(1)

C(14) 0.7177(2) 0.5424(1) –0.0532(2) 0.038(1) H(181) 0.812(2) 0.703(1) –0.164(2) 0.06(1)

C(15) 0.5132(2) 0.5076(1) –0.2899(2) 0.048(1) H(182) 0.820(2) 0.790(2) –0.077(2) 0.07(1)

H(183) 0.951(3) 0.722(1) –0.004(3) 0.07(1)

* Ueq = (1/3) .

U iso* U iso

*

Uijai*a j

* ai a j⋅( )j∑i∑

Table 3. Torsion angles (deg) for non-hydrogen atoms and dihedral angles (deg) between the planes of benzene (1), pyrimi-dine (2), and pyridone (3) rings of the molecule (e.s.d.'s are given in parentheses)

C(12)–C(1)–C(2)–C(3) –0.0(3) C(6)–C(7)–C(8)–C(9) –1.7(3)

C(2)–C(1)–C(12)–C(13) –1.9(3) C(7)–C(8)–C(9)–N(10) 2.2(3)

C(1)–C(2)–C(3)–C(4) 1.4(3) C(8)–C(9)–N(10)–C(14) 0.1(2)

C(2)–C(3)–C(4)–C(13) –0.8(3) C(14)–N(10)–C(11)–C(12) 37.3(2)

C(3)–C(4)–C(13)–C(12) –1.1(3) C(9)–N(10)–C(14)–C(6) –2.8(2)

C(14)–N(5)–C(13)–C(12) 23.5(2) C(11)–N(10)–C(14)–N(5) –9.5(2)

C(13)–N(5)–C(14)–N(10) –23.1(2) N(10)–C(11)–C(12)–C(13) –36.0(2)

C(14)–C(6)–C(7)–C(8) –1.1(3) C(1)–C(12)–C(13)–C(4) 2.4(3)

C(7)–C(6)–C(14)–N(10) 3.3(3) C(11)–C(12)–C(13)–N(5) 8.6(3)

Plane Plane Angle

1 2 16.12(5)

1 3 28.61(5)

2 3 12.77(5)

CRYSTALLOGRAPHY REPORTS Vol. 45 No. 4 2000

X-RAY STRUCTURE ANALYSIS 613

RESULTS AND DISCUSSION

The final atomic coordinates and equivalent isotro-pic thermal parameters for the non-hydrogen (isotropicfor hydrogen) atoms are given in Table 2. The endocy-clic torsion angles and dihedral angles between differ-ent least-squares planes are listed in Table 3. A generalview of the molecule and the atomic numbering scheme[15] is shown in the figure.

The bond distances of the molecule, on the whole,agree with the values reported for some analogousstructures containing quinazoline or pyrimidine rings[16–19]. The mean value [1.392(2) Å] of the twoC(sp2)–N bonds, i.e., N(5)–C(13) [1.419(2) Å] andN(5)–C(14) [1.366(2) Å], is in agreement with the stan-dard mean value of 1.385 Å[20]; the length of the bondN(5)–C(13) is close to the values obtained in E- and Z-isomers of 1-(-2-amino-1-cyano-2-thioethylene)pyri-dinium-ylide [21]. The C(9)=O(3) bond length [1.255(2)Å] is greater than its theoretical value [1.199 Å], and itmay probably be due to the strong intramolecularO(2)–H(17)⋅⋅⋅O(3) hydrogen bond. The benzene ring is

C(3)

C(4)

C(2)

C(1)

C(13)

C(12)

C(11)

C(18)

C(16)

C(15) C(6)C(7)

C(8)

C(9)

C(17)

O(1)

O(2)

O(3)

N(10)

A general view of the molecule and atomic numberingscheme.

N(5)

C(14)

Table 4. Inter- and intramolecular hydrogen bonds

BondD–H···A H···A, Å D···A, Å D–H···A,

deg

C(11)–H(111)···O(3) 2.19(2) 2.658(2) 109(1)

C(18)–H(183)···O(3) 2.81(2) 3.285(2) 109(2)

O(2)–H(17)···O(3) 1.56(3) 2.514(2) 156(3)

C(15)–H(152)···O(2)(i) 2.67(2) 3.426(2) 131(1)

C(4)–H(4)···O(2)(i) 2.70(2) 3.594(2) 159(2)

C(16)–H(162)···N(10)(ii) 2.78(4) 3.479(4) 123(2)

Note: Symmetrical transformations: (i) –1 + x, y, −1 + z; (ii) 1 – x,1 – y, –z).

CRYSTALLOGRAPHY REPORTS Vol. 45 No. 4 200

perfectly planar, and the pyridone ring deviates slightlyfrom planarity [the maximum deviation is –0.023 Å forthe C(14) atom]. The pyrimidine ring has an 11β-sofaconformation with the asymmetry parameter ∆Cs[C(11)] = 0.87 [22]. The dihedral angle between theleast squares plane of benzene and pyridone rings is28.61(5)°, indicating that the molecule is somewhatfolded, may be due to the sofa conformation of the pyri-midine ring.

The molecular packing in the crystal is of the her-ring-bone type. The following intra- and intermolecu-lar bonds have been found to contribute to the stabilityof the crystal structure: O–H···O, C–H···O, andC−H···N (Table 4).

ACKNOWLEDGMENTS

Rajnikant is grateful to Dr. K. L. Dhar, Scientist,Natural Products Chemistry Division, RegionalResearch Laboratory, Jammu Tawi, for supplying thesamples. He further acknowledges the financial supportreceived under Special Assistance Program (SAP) ofthe University Grants Commission (DSA-Phase III),Government of India, New Delhi.

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