C—H...O hydrogen-bonding and C—H...π inter­actions in 3-(4-fluoro­phen­yl)-1,5,7-trimethyl-1,2,3,4-tetra­hydro­pyrido[2,3-d]pyrimidine-2,4-dione

In the title compound, C₁₆H₁₄FN₃O₂, a diverse set of weak inter­molecular C—H...π, π–π and C—H...O inter­actions link the mol­ecules into sheets. The C—H...O inter­actions generate centrosymmetric rings with a graph-set motif of R₂²(14) and chains with a C(8) motif.

S1. Comment

Fused pyrido[2,3-d]pyrimidines, the 5-deza analogues of pteridines, are known to possess a variety of biological properties (Heber et al., 1993) and have been reported as dihydrofolate reductase inhibitors and antitumor and antihypertensive agents (Cody et al., 2002; Ellingboe, 1995; Dave & Shukla, 2000). In the absence of potential donor and acceptor groups in the heterocyclic compound, non-conventional weak intermolecular forces, such as C—H···π and π–π interactions, contribute to the stability of the molecular structure.

As part of a systematic investigation of heterocyclic compounds (Patel et al., 2002; Jotani et al., 2006), in the present study we report the molecular structure of the title compound, (I). A view of the molecule is shown in Fig. 1. The molecule contains a fused ring system between pyridine and pyrimidine; the C—N distances vary from 1.332 (3) to 1.470 (3) Å and the variation of the endocyclic angles at the N atoms is from 116.88 (19) to 125.28 (17)° (Table 1). A similar structural feature is also reported for piromidic acid (Song et al., 1998) and pipemidic acid (Fonseca et al., 1986). Least-square plane calculations show that the fused pyridopyrimidine ring system is planar; the dihedral angle between the two ring planes is 3.26 (11)°. The r.m.s. deviation of the atoms of the fused rings from the mean plane through the rings is 0.033 Å with a maximum deviation of 0.0599 (16) Å for atom N7.

All three methyl and the two O-atom substituents almost share the plane of the ring to which they are bonded, as shown by the torsion angles in Table 1. The plane of the flurophenyl ring (C16–C21) is almost orthogonal [75.21 (10)°] to that of the fused ring system, thus minimizing intramolecular interactions with this moiety. The F atom is not involved in any intermolecular interactions, unlike the Br···π interactions reported in the lattice inclusion compounds of 1,4,8,11-tetrabromo-5bα,6,12bα,13- tetrahydropentaleno[1,2 - b:4,5 - b']diquinoline (Rahman et al., 2004). The closest approach to atom F22 in (I) is the methyl C atom, C15 [F22···C15(x, y, -1 + z) = 3.158 (4) Å].

The packing (Fig. 2) of the molecules is mainly stabilized by C—H···O and C—H···π interactions (Table 2). Two significant C—H···π interactions exist between the C12 and C15 methyl groups and the π-electron clouds of the flurophenyl ring and the pyrimidine ring (C5/C6/N7/C8/N9/C10), respectively, in neighbouring molecules. According to a classification of Malone et al. (1997), one of the C—H···π interactions, C15—H153···Cg1^iv (Cg1 is the centre of gravity of the pyrimidine ring; all symmetry codes are as in Table 2), very much belongs to the classical geometry type-I interaction, i.e. the type T interaction with the C15—H153 bond pointing towards the center of the acceptor ring. The H153···Cg1^iv distance is 2.71 Å, the C15—H153···Cg1^iv angle is 158°, the angle of approach of the H153···Cg1^iv vector to the plane of the aromatic ring is 84.3° and the distance of the projection of the H153···Cg1^iv vector onto the ring plane from the centre of the ring is 0.029 Å. In the other C—H···π interaction, which involves the π-system of the fluorophenyl ring, C12—H123···Cg2^v (Cg2 is the centre of gravity of the fluorophenyl ring) forms a type-III geometry; the H123···Cg2^v distance is 3.00 Å, the C12—H123···Cg2^v angle is 133°, the angle of approach of the H123···Cg2^v vector to the plane of the flurophenyl ring is 86.6° and the distance of projection of the H123···Cg2^v vector onto the ring plane from the centre of the ring is 0.189 Å.

Parallel to the [100] direction, each molecule is connected on each side by a pair of centrosymmetrically related C—H···O interactions to its neighbour. On one side of the reference molecule, the C18—H18···O13ⁱⁱ and C18ⁱⁱ—H18ⁱⁱ···O13 interactions complete a ring, which can be described by a graph-set motif of R²₂(14) (Fig. 3) (Bernstein et al., 1995). On the other side of the reference molecule, the C20—H20···O13ⁱⁱⁱ and C20ⁱⁱⁱ—H20ⁱⁱⁱ···O13 interactions complete another ring of the same size. Together, the interactions link the molecules into a ladder that runs parallel to the [100] direction. In addition, the molecules are linked by the C3—H3···O14ⁱ interaction into chains that run along [010] and can be described by a C(8) graph-set motif. The described chains and rings combine to form molecular sheets, which lie parallel to the (001) plane. The π–π and C—H···π interactions also occur within these sheets. The π–π interaction involves two centrosymmetrically related [at (x, y, z) and (2 - x, -y, 2 - z)] pyrimidine rings where the centroids of the two rings are separated by 3.871 (4) Å (Fig. 2).

Related literature

For related literature, see: Bernstein et al. (1995); Cody et al. (2002); Dave & Shukla (2000); Ellingboe (1995); Fonseca et al. (1986); Heber et al. (1993); Jotani et al. (2006); Malone et al. (1997); Patel et al. (2002); Rahman et al. (2004); Song et al. (1998); Thaker (2004).

S2. Experimental

The synthesis of the title compound was reported by Thaker (2004). Single crystals (m.p. 483 K) were grown by slow evaporation from a solution of the compound in ethyl acetate with a layer of ethyl alcohol and a few traces of dimethylformamide over it. The crystal density was measured by the flotation method [flotation in what?].

S3. Refinement

All H atoms were placed in geometrically idealized positions with C—H distances of 0.96 Å (methyl) or 0.93 Å (aromatic) and constrained to ride on their parent atoms with U_iso(H) values of 1.2U_eq(C) for the phenyl H atoms and 1.5U_eq(C) for the methyl H atoms.

Computing details

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software; data reduction: XCAD4 in WinGX (Farrugia, 1999); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular structure of (I), showing the atom-labelling scheme and 50% probability displacement ellipsoids.
	Fig. 2. The molecular packing of (I), showing the C—H···π interactions as dashed lines and π–π interaction as solid lines. H atoms not involved in these interactions have been omitted.
	Fig. 3. The crystal packing of (I), showing the formation of rings, chains and sheets via the C—H···O interactions. H atoms not involved in these interactions have been omitted. [Symmetry codes: (i) x - 1, y, z; (ii) x, y + 1, z; (iii) -x + 1, -y, -z + 1; (iv) x - 1, y + 1, z.]

3-(4-fluorophenyl)-1,5,7-trimethyl-1,2,3,4- tetrahydropyrido[2,3-d]pyrimidine-2,4-dione

Crystal data

C16H14FN3O2	Z = 2
Mr = 299.30	F(000) = 312
Triclinic, P1	Dx = 1.366 Mg m^−3 Dm = 1.354 Mg m^−3 Dm measured by floation method
Hall symbol: -P 1	Melting point: 483 K
a = 7.358 (7) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.377 (3) Å	Cell parameters from 25 reflections
c = 10.758 (4) Å	θ = 10–25°
α = 97.53 (3)°	µ = 0.10 mm^−1
β = 97.09 (3)°	T = 293 K
γ = 93.96 (5)°	Needle, colourless
V = 727.5 (8) Å^3	0.3 × 0.2 × 0.2 mm

Data collection

Enraf–Nonius CAD-4 diffractometer	1765 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.010
Graphite monochromator	θmax = 25.0°, θmin = 2.2°
ω–2θ scans	h = 0→8
Absorption correction: ψ scan (North et al., 1968)	k = −11→11
Tmin = 0.955, Tmax = 0.996	l = −12→12
2776 measured reflections	2 standard reflections every 60 min
2559 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.054	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.167	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.1004P)^2 + 0.1095P] where P = (Fo^2 + 2Fc^2)/3
2559 reflections	(Δ/σ)max < 0.001
202 parameters	Δρmax = 0.19 e Å^−3
0 restraints	Δρmin = −0.29 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
F22	0.7109 (4)	0.3222 (2)	0.38610 (15)	0.1229 (8)
N1	0.7323 (3)	−0.18573 (19)	1.10379 (18)	0.0540 (5)
N7	0.7673 (3)	0.02463 (17)	0.79753 (16)	0.0491 (5)
N9	0.7497 (2)	0.02478 (17)	1.01424 (16)	0.0472 (5)
O13	0.7982 (2)	−0.17994 (16)	0.66763 (15)	0.0652 (5)
O14	0.7549 (3)	0.23360 (15)	0.92862 (15)	0.0666 (5)
C2	0.7337 (3)	−0.3302 (2)	1.0933 (2)	0.0614 (6)
C3	0.7593 (4)	−0.4136 (2)	0.9821 (3)	0.0666 (7)
H3	0.7637	−0.5128	0.9800	0.080*
C4	0.7783 (3)	−0.3527 (2)	0.8744 (2)	0.0575 (6)
C5	0.7730 (3)	−0.2013 (2)	0.8825 (2)	0.0462 (5)
C6	0.7814 (3)	−0.1248 (2)	0.7741 (2)	0.0486 (5)
C8	0.7572 (3)	0.1032 (2)	0.9158 (2)	0.0477 (5)
C10	0.7516 (3)	−0.1256 (2)	1.0002 (2)	0.0450 (5)
C11	0.7040 (5)	−0.3984 (3)	1.2088 (3)	0.0862 (9)
H111	0.7895	−0.3519	1.2796	0.129*
H112	0.7229	−0.4992	1.1939	0.129*
H113	0.5807	−0.3877	1.2269	0.129*
C12	0.8057 (5)	−0.4474 (3)	0.7549 (3)	0.0831 (9)
H121	0.9206	−0.4169	0.7288	0.125*
H122	0.7071	−0.4397	0.6894	0.125*
H123	0.8068	−0.5459	0.7703	0.125*
C15	0.7326 (3)	0.1068 (2)	1.1378 (2)	0.0543 (6)
H151	0.7666	0.2073	1.1369	0.081*
H152	0.8123	0.0721	1.2027	0.081*
H153	0.6077	0.0946	1.1546	0.081*
C16	0.7561 (3)	0.1032 (2)	0.6898 (2)	0.0525 (6)
C17	0.9085 (4)	0.1354 (3)	0.6345 (2)	0.0691 (7)
H17	1.0221	0.1081	0.6666	0.083*
C18	0.8932 (5)	0.2085 (3)	0.5309 (3)	0.0860 (9)
H18	0.9954	0.2303	0.4918	0.103*
C19	0.7255 (5)	0.2481 (3)	0.4874 (2)	0.0805 (9)
C20	0.5725 (5)	0.2173 (3)	0.5402 (3)	0.0796 (8)
H20	0.4596	0.2455	0.5078	0.095*
C21	0.5872 (4)	0.1431 (3)	0.6428 (2)	0.0667 (7)
H21	0.4837	0.1201	0.6803	0.080*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
F22	0.217 (2)	0.1118 (15)	0.0566 (10)	0.0494 (15)	0.0316 (12)	0.0417 (10)
N1	0.0654 (12)	0.0403 (10)	0.0594 (11)	0.0069 (8)	0.0105 (9)	0.0148 (8)
N7	0.0652 (11)	0.0346 (9)	0.0493 (10)	0.0071 (8)	0.0120 (8)	0.0066 (7)
N9	0.0626 (11)	0.0323 (9)	0.0473 (10)	0.0057 (8)	0.0091 (8)	0.0055 (7)
O13	0.0930 (13)	0.0480 (9)	0.0561 (10)	0.0127 (8)	0.0198 (9)	−0.0002 (7)
O14	0.1088 (14)	0.0307 (8)	0.0615 (10)	0.0107 (8)	0.0122 (9)	0.0075 (7)
C2	0.0715 (16)	0.0414 (13)	0.0753 (16)	0.0070 (11)	0.0134 (13)	0.0191 (11)
C3	0.0824 (17)	0.0326 (11)	0.0892 (18)	0.0089 (11)	0.0190 (14)	0.0164 (12)
C4	0.0638 (14)	0.0353 (11)	0.0739 (16)	0.0066 (10)	0.0137 (12)	0.0037 (10)
C5	0.0492 (12)	0.0338 (10)	0.0559 (12)	0.0053 (9)	0.0080 (10)	0.0056 (9)
C6	0.0545 (13)	0.0364 (11)	0.0543 (13)	0.0071 (9)	0.0086 (10)	0.0012 (9)
C8	0.0598 (13)	0.0324 (11)	0.0508 (12)	0.0042 (9)	0.0074 (10)	0.0060 (9)
C10	0.0449 (11)	0.0348 (11)	0.0556 (13)	0.0043 (9)	0.0070 (9)	0.0074 (9)
C11	0.122 (3)	0.0570 (16)	0.090 (2)	0.0107 (16)	0.0251 (18)	0.0366 (14)
C12	0.123 (2)	0.0351 (12)	0.095 (2)	0.0146 (14)	0.0354 (18)	−0.0003 (12)
C15	0.0690 (15)	0.0441 (12)	0.0500 (12)	0.0084 (10)	0.0109 (11)	0.0027 (9)
C16	0.0725 (15)	0.0381 (11)	0.0476 (12)	0.0086 (10)	0.0086 (11)	0.0068 (9)
C17	0.0829 (18)	0.0679 (16)	0.0661 (16)	0.0200 (13)	0.0260 (14)	0.0229 (12)
C18	0.120 (3)	0.083 (2)	0.0708 (18)	0.0277 (18)	0.0464 (18)	0.0287 (15)
C19	0.143 (3)	0.0614 (16)	0.0412 (13)	0.0257 (18)	0.0148 (16)	0.0119 (11)
C20	0.104 (2)	0.0697 (17)	0.0639 (16)	0.0184 (16)	−0.0065 (16)	0.0174 (13)
C21	0.0748 (17)	0.0552 (14)	0.0713 (16)	0.0073 (12)	0.0060 (13)	0.0162 (12)

Geometric parameters (Å, º)

F22—C19	1.364 (3)	C11—H111	0.9600
N1—C10	1.332 (3)	C11—H112	0.9600
N1—C2	1.346 (3)	C11—H113	0.9600
N7—C8	1.397 (3)	C12—H121	0.9600
N7—C6	1.404 (3)	C12—H122	0.9600
N7—C16	1.450 (3)	C12—H123	0.9600
N9—C8	1.371 (3)	C15—H151	0.9600
N9—C10	1.399 (3)	C15—H152	0.9600
N9—C15	1.470 (3)	C15—H153	0.9600
O13—C6	1.218 (3)	C16—C17	1.366 (4)
O14—C8	1.214 (2)	C16—C21	1.378 (4)
C2—C3	1.382 (3)	C17—C18	1.381 (3)
C2—C11	1.503 (3)	C17—H17	0.9300
C3—C4	1.375 (4)	C18—C19	1.358 (4)
C3—H3	0.9300	C18—H18	0.9300
C4—C5	1.414 (3)	C19—C20	1.352 (5)
C4—C12	1.508 (3)	C20—C21	1.377 (4)
C5—C10	1.400 (3)	C20—H20	0.9300
C5—C6	1.452 (3)	C21—H21	0.9300
C10—N1—C2	116.88 (19)	H111—C11—H113	109.5
C8—N7—C6	125.28 (17)	H112—C11—H113	109.5
C8—N7—C16	117.23 (16)	C4—C12—H121	109.5
C6—N7—C16	117.45 (17)	C4—C12—H122	109.5
C8—N9—C10	123.17 (18)	H121—C12—H122	109.5
C8—N9—C15	116.29 (17)	C4—C12—H123	109.5
C10—N9—C15	120.50 (17)	H121—C12—H123	109.5
N1—C2—C3	122.4 (2)	H122—C12—H123	109.5
N1—C2—C11	116.7 (2)	N9—C15—H151	109.5
C3—C2—C11	120.9 (2)	N9—C15—H152	109.5
C4—C3—C2	121.2 (2)	H151—C15—H152	109.5
C4—C3—H3	119.4	N9—C15—H153	109.5
C2—C3—H3	119.4	H151—C15—H153	109.5
C3—C4—C5	117.4 (2)	H152—C15—H153	109.5
C3—C4—C12	119.6 (2)	C17—C16—C21	120.5 (2)
C5—C4—C12	123.0 (2)	C17—C16—N7	121.1 (2)
C10—C5—C4	117.3 (2)	C21—C16—N7	118.5 (2)
C10—C5—C6	119.90 (18)	C16—C17—C18	119.8 (3)
C4—C5—C6	122.80 (19)	C16—C17—H17	120.1
O13—C6—N7	119.09 (19)	C18—C17—H17	120.1
O13—C6—C5	125.39 (19)	C19—C18—C17	118.6 (3)
N7—C6—C5	115.52 (18)	C19—C18—H18	120.7
O14—C8—N9	122.80 (19)	C17—C18—H18	120.7
O14—C8—N7	120.92 (18)	C20—C19—C18	122.8 (2)
N9—C8—N7	116.27 (17)	C20—C19—F22	118.6 (3)
N1—C10—N9	115.49 (18)	C18—C19—F22	118.5 (3)
N1—C10—C5	124.89 (18)	C19—C20—C21	118.7 (3)
N9—C10—C5	119.63 (19)	C19—C20—H20	120.7
C2—C11—H111	109.5	C21—C20—H20	120.7
C2—C11—H112	109.5	C20—C21—C16	119.7 (3)
H111—C11—H112	109.5	C20—C21—H21	120.2
C2—C11—H113	109.5	C16—C21—H21	120.2
C10—N1—C2—C3	1.9 (4)	C16—N7—C8—N9	173.76 (19)
C10—N1—C2—C11	−177.6 (2)	C2—N1—C10—N9	−179.98 (19)
N1—C2—C3—C4	−2.3 (4)	C2—N1—C10—C5	0.0 (3)
C11—C2—C3—C4	177.1 (2)	C8—N9—C10—N1	−176.10 (19)
C2—C3—C4—C5	0.7 (4)	C15—N9—C10—N1	1.7 (3)
C2—C3—C4—C12	−179.9 (2)	C8—N9—C10—C5	3.9 (3)
C3—C4—C5—C10	1.0 (3)	C15—N9—C10—C5	−178.32 (19)
C12—C4—C5—C10	−178.3 (2)	C4—C5—C10—N1	−1.5 (3)
C3—C4—C5—C6	−176.5 (2)	C6—C5—C10—N1	176.16 (19)
C12—C4—C5—C6	4.1 (4)	C4—C5—C10—N9	178.52 (18)
C8—N7—C6—O13	−176.4 (2)	C6—C5—C10—N9	−3.8 (3)
C16—N7—C6—O13	5.8 (3)	C8—N7—C16—C17	105.8 (3)
C8—N7—C6—C5	4.0 (3)	C6—N7—C16—C17	−76.2 (3)
C16—N7—C6—C5	−173.85 (18)	C8—N7—C16—C21	−75.1 (3)
C10—C5—C6—O13	−179.4 (2)	C6—N7—C16—C21	102.9 (2)
C4—C5—C6—O13	−1.9 (4)	C21—C16—C17—C18	0.0 (4)
C10—C5—C6—N7	0.2 (3)	N7—C16—C17—C18	179.1 (2)
C4—C5—C6—N7	177.66 (19)	C16—C17—C18—C19	0.7 (4)
C10—N9—C8—O14	179.8 (2)	C17—C18—C19—C20	−0.9 (5)
C15—N9—C8—O14	1.9 (3)	C17—C18—C19—F22	179.1 (2)
C10—N9—C8—N7	−0.1 (3)	C18—C19—C20—C21	0.3 (4)
C15—N9—C8—N7	−177.94 (18)	F22—C19—C20—C21	−179.7 (2)
C6—N7—C8—O14	176.1 (2)	C19—C20—C21—C16	0.5 (4)
C16—N7—C8—O14	−6.1 (3)	C17—C16—C21—C20	−0.6 (4)
C6—N7—C8—N9	−4.0 (3)	N7—C16—C21—C20	−179.7 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3···O14^i	0.93	2.36	3.280 (4)	168
C18—H18···O13^ii	0.93	2.45	3.305 (5)	153
C20—H20···O13^iii	0.93	2.49	3.274 (5)	142
C15—H153···Cg1^iv	0.96	2.71	3.617 (4)	158
C12—H123···Cg2^i	0.96	3.00	3.716 (5)	133

Symmetry codes: (i) x, y−1, z; (ii) −x+2, −y, −z+1; (iii) −x+1, −y, −z+1; (iv) −x+1, −y, −z+2.