1,3-Dimethyl-2-oxo-4,6-diphenyl-1,2,3,4-tetrahydropyridine-3-carbonitrile

The crystal structure of the title compound, C₂₀H₁₈N₂O, reveals a distorted half-chair conformation of the central tetra­hydro­pyridine (THP) ring, with the cyano- and adjacent phenyl-substituted C atoms displaced by 0.329 (1) and -0.315 (1) Å, respectively, from the THP best plane. Steric interactions force the phenyl rings out of the THP plane by 49.21 (9) and 65.76 (5)°. The cyano moiety is coplanar with the THP plane.

S1. Comment

In order to study the influence of substituents of different sizes upon the structural parameters of the molecule, we report here the crystal structure of 1,3-dimethyl-2-oxo-4,6-diphenyl-1,2,3,4-tetrahydropyridine-3-carbonitrile, (I). The crystal structures of the analogous diethyl and dibenzyl derivatives of tetrahydropyridine have previously been reported (Patel et al., 2001b,c). \sch

Fig. 1. depicts the structure of the molecule of (I), and selected bond lengths and angles are given in Table 1. The structure of (I) has the same characteristic molecular dimensions as observed for similar compounds of this class (Patel et al., 2001b,c). The bonds C1—C2, C2—C3 and C3—C4 [1.548 (2), 1.554 (2) and 1.494 (2) Å, respectively] have predominantly single-bond character, whereas the C1—N1 distance of 1.361 (2) Å is a partial double bond. The lengthening of C2—C3 and C3—C4, and the contraction of the C2—C3—C4 angle, [107.9 (1)°] may be attributed to the comparatively heavy substituent at C3 (a phenyl ring). These values are similar to those found in the other derivatives of THP that we have recently reported (Patel et al., 2001b,c).

The triple-bond character of C18—N2 [1.135 (3) Å], and the C2—C18—N2 angle of 177.8 (2)° defining the linearity of the cyano moiety, are typical of this group of 3-cyano-2-pyridine compounds (Black et al., 1992; Hussain et al., 1996; Patel, 2001a).

The methyl group at C2 is out of the plane of the THP ring by 0.627 (3) Å, whereas that at N1 is coplanar with the THP plane. Both the phenyl rings are planar within themselves. Steric interactions force the phenyl rings out of the THP plane by 49.21 (9) and 65.76 (5)°, respectively. However, these dihedral angles are in a much smaller range than those reported for similar compounds (Patel et al., 2001b,c; Hursthouse et al., 1992).

The torsion angles about C2—C18 are as follows, with values for the diethyl and dibenzyl substituents, respectively, given inside the brackets: C1—C2—C18—N2 = 107 (5)° [-126 (8) and -164 (2)°] and C3—C2—C18—N2 = -136 (5)° [113 (8) and 74 (2)°]. These observations reveal that the molecular conformation in all these compounds differs significantly about the C2—C18 bond.

In summary, these results show that, although the molecule of (I) preserves the same characteristic molecular dimensions as analogous compounds, the molecular conformation is influenced by the size of the substituents. As usual in heterocyclic compounds, weak van der Waals forces are responsible for the stability of the structure.

The three Patel et al. (2001) references each need a unique identifier. The a, b and c used above need careful checking to ensure the correct citation is given in each place. Please provide any corrections necessary.

S2. Experimental

Compound (I) was synthesized according to the method of Shah (2000). Full details of the synthesis will be published elsewhere by Dave et al. Thin needle-shaped crystals of (I) were grown from chloroform-ethanol solution by slow evaporation. The crystal density was measured by flotation in an aqueous potassium iodide solution.

S3. Refinement

H atoms were treated as riding, with C—H = 0.93–0.98 Å, and U_iso(H) = 1.5U_eq(C) for methyl H and 1.2U_eq(C) for all others. Are these the correct constraints?

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software (Enraf-Nonius, 1989); data reduction: MolEN (Nonius, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick 1990); program(s) used to refine structure: SHELXL97 (Sheldrick 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. A view of the molecular structure of (I) showing 50% probability displacement ellipsoids. H atoms have been omitted for clarity.

1,3-dimethyl-2-oxo-4,6-diphenyl-1,2,3,4-tetrahydropyridine-3-carbonitrile

Crystal data

C20H18N2O	F(000) = 640
Mr = 302.36	Dx = 1.214 Mg m^−3 Dm = 1.204 Mg m^−3 Dm measured by flotation
Monoclinic, P21/c	Cu Kα radiation, λ = 1.54180 Å
a = 13.738 (3) Å	Cell parameters from 25 reflections
b = 7.4751 (16) Å	θ = 25–35°
c = 17.1566 (18) Å	µ = 0.60 mm^−1
β = 110.117 (13)°	T = 293 K
V = 1654.4 (5) Å^3	Needle, colourless
Z = 4	0.2 × 0.1 × 0.1 mm

Data collection

Enraf-Nonius CAD-4 diffractometer	2548 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.029
Graphite monochromator	θmax = 68.0°, θmin = 3.4°
ω/2θ scans	h = 0→16
Absorption correction: empirical (using intensity measurements) via ψ scan (North et al., 1968)	k = 0→8
Tmin = 0.931, Tmax = 0.942	l = −20→19
3141 measured reflections	2 standard reflections every 60 min
3141 independent reflections	intensity decay: 1%

Refinement

Refinement on F^2	H-atom parameters constrained
Least-squares matrix: full
R[F^2 > 2σ(F^2)] = 0.046	(Δ/σ)max = 0.034
wR(F^2) = 0.141	Δρmax = 0.36 or 0.46? e Å^−3
S = 1.06	Δρmin = −0.23 or −0.18? e Å^−3
3010 reflections	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
220 parameters	Extinction coefficient: 0.0042 (5)

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.

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
O1	0.77347 (14)	0.2377 (2)	0.43189 (12)	0.0884 (8)	1.013 (6)
N1	0.82256 (11)	−0.0167 (2)	0.38443 (9)	0.0534 (4)
N2	0.73306 (17)	−0.2059 (3)	0.56059 (12)	0.0863 (6)
C5	0.79970 (13)	−0.1966 (2)	0.35755 (10)	0.0479 (4)
C4	0.70478 (12)	−0.2589 (2)	0.34080 (10)	0.0481 (4)
H4	0.6907	−0.3777	0.3247	0.058*
C3	0.61949 (13)	−0.1424 (2)	0.34718 (10)	0.0467 (4)
H3	0.5991	−0.0641	0.2984	0.056*
C2	0.66548 (14)	−0.0194 (2)	0.42420 (11)	0.0512 (4)
C1	0.75905 (15)	0.0806 (3)	0.41405 (12)	0.0574 (5)
C20	0.90697 (17)	0.0788 (3)	0.36906 (14)	0.0701 (6)
H20A	0.9462	−0.0035	0.3486	0.105*
H20B	0.9514	0.1315	0.4199	0.105*
H20C	0.8788	0.1710	0.3286	0.105*
C12	0.88503 (13)	−0.3076 (2)	0.34924 (10)	0.0485 (4)
C13	0.97872 (15)	−0.3286 (3)	0.41369 (12)	0.0635 (5)
H13	0.9908	−0.2663	0.4631	0.076*
C14	1.05406 (16)	−0.4411 (3)	0.40519 (14)	0.0718 (6)
H14	1.1167	−0.4534	0.4488	0.086*
C15	1.03754 (16)	−0.5343 (3)	0.33358 (15)	0.0681 (6)
H15	1.0883	−0.6111	0.3285	0.082*
C16	0.94566 (16)	−0.5142 (3)	0.26894 (13)	0.0630 (5)
H16	0.9343	−0.5772	0.2199	0.076*
C17	0.86985 (14)	−0.4009 (2)	0.27638 (11)	0.0521 (4)
H17	0.8081	−0.3872	0.2320	0.062*
C6	0.52275 (12)	−0.2408 (2)	0.34581 (10)	0.0453 (4)
C7	0.52640 (13)	−0.3973 (2)	0.38960 (11)	0.0489 (4)
H7	0.5902	−0.4470	0.4201	0.059*
C8	0.43610 (14)	−0.4808 (3)	0.38843 (12)	0.0562 (5)
H8	0.4398	−0.5859	0.4183	0.067*
C9	0.34157 (14)	−0.4106 (3)	0.34381 (13)	0.0640 (5)
H9	0.2811	−0.4657	0.3443	0.077*
C10	0.33677 (15)	−0.2578 (3)	0.29831 (17)	0.0760 (7)
H10	0.2727	−0.2106	0.2666	0.091*
C11	0.42643 (15)	−0.1743 (3)	0.29955 (14)	0.0661 (5)
H11	0.4221	−0.0707	0.2685	0.079*
C18	0.70442 (15)	−0.1267 (3)	0.50049 (12)	0.0578 (5)
C19	0.58755 (18)	0.1167 (3)	0.43317 (15)	0.0721 (6)
H19A	0.5620	0.1874	0.3836	0.108*
H19B	0.6207	0.1932	0.4797	0.108*
H19C	0.5308	0.0552	0.4419	0.108*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.1115 (14)	0.0549 (10)	0.1181 (15)	−0.0284 (8)	0.0642 (11)	−0.0326 (9)
N1	0.0604 (9)	0.0502 (9)	0.0569 (8)	−0.0159 (7)	0.0296 (7)	−0.0095 (7)
N2	0.0972 (15)	0.1006 (16)	0.0549 (10)	−0.0116 (12)	0.0182 (10)	0.0084 (10)
C5	0.0538 (9)	0.0494 (9)	0.0436 (8)	−0.0082 (8)	0.0207 (7)	−0.0062 (7)
C4	0.0505 (9)	0.0482 (9)	0.0490 (9)	−0.0073 (7)	0.0213 (7)	−0.0094 (7)
C3	0.0545 (9)	0.0441 (9)	0.0439 (8)	−0.0028 (7)	0.0199 (7)	0.0018 (7)
C2	0.0629 (10)	0.0438 (9)	0.0532 (9)	−0.0020 (8)	0.0279 (8)	−0.0031 (7)
C1	0.0715 (12)	0.0470 (10)	0.0590 (10)	−0.0134 (9)	0.0292 (9)	−0.0095 (8)
C20	0.0729 (13)	0.0680 (13)	0.0803 (14)	−0.0278 (11)	0.0404 (11)	−0.0133 (11)
C12	0.0491 (9)	0.0521 (10)	0.0494 (9)	−0.0088 (7)	0.0234 (7)	−0.0033 (7)
C13	0.0592 (11)	0.0770 (14)	0.0533 (10)	−0.0043 (10)	0.0181 (9)	−0.0077 (10)
C14	0.0522 (11)	0.0845 (15)	0.0765 (13)	0.0015 (10)	0.0193 (10)	0.0058 (12)
C15	0.0623 (12)	0.0640 (12)	0.0905 (15)	0.0002 (10)	0.0423 (11)	0.0014 (11)
C16	0.0734 (13)	0.0620 (12)	0.0680 (12)	−0.0109 (10)	0.0427 (10)	−0.0106 (9)
C17	0.0556 (10)	0.0564 (10)	0.0497 (9)	−0.0102 (8)	0.0251 (8)	−0.0047 (8)
C6	0.0461 (9)	0.0450 (9)	0.0459 (8)	0.0028 (7)	0.0171 (7)	0.0025 (7)
C7	0.0468 (9)	0.0471 (9)	0.0522 (9)	0.0036 (7)	0.0165 (7)	0.0052 (7)
C8	0.0592 (11)	0.0522 (10)	0.0627 (11)	−0.0042 (8)	0.0280 (9)	0.0031 (8)
C9	0.0482 (10)	0.0673 (13)	0.0819 (13)	−0.0059 (9)	0.0294 (9)	−0.0069 (11)
C10	0.0444 (10)	0.0729 (14)	0.1014 (17)	0.0118 (10)	0.0134 (10)	0.0086 (13)
C11	0.0555 (11)	0.0585 (12)	0.0763 (13)	0.0086 (9)	0.0122 (9)	0.0191 (10)
C18	0.0653 (11)	0.0619 (12)	0.0491 (10)	−0.0101 (9)	0.0233 (9)	−0.0072 (9)
C19	0.0837 (14)	0.0550 (12)	0.0917 (15)	0.0041 (10)	0.0481 (13)	−0.0091 (11)

Geometric parameters (Å, º)

O1—C1	1.212 (2)	C14—C15	1.362 (3)
N1—C1	1.361 (2)	C14—H14	0.9300
N1—C5	1.421 (2)	C15—C16	1.372 (3)
N1—C20	1.461 (2)	C15—H15	0.9300
N2—C18	1.135 (3)	C16—C17	1.382 (3)
C5—C4	1.320 (2)	C16—H16	0.9300
C5—C12	1.482 (2)	C17—H17	0.9300
C4—C3	1.494 (2)	C6—C11	1.380 (2)
C4—H4	0.9300	C6—C7	1.382 (2)
C3—C6	1.512 (2)	C7—C8	1.383 (2)
C3—C2	1.555 (2)	C7—H7	0.9300
C3—H3	0.9800	C8—C9	1.366 (3)
C2—C18	1.470 (3)	C8—H8	0.9300
C2—C19	1.522 (3)	C9—C10	1.372 (3)
C2—C1	1.548 (2)	C9—H9	0.9300
C20—H20A	0.9600	C10—C11	1.374 (3)
C20—H20B	0.9600	C10—H10	0.9300
C20—H20C	0.9600	C11—H11	0.9300
C12—C17	1.383 (2)	C19—H19A	0.9600
C12—C13	1.387 (3)	C19—H19B	0.9600
C13—C14	1.380 (3)	C19—H19C	0.9600
C13—H13	0.9300
C1—N1—C5	121.87 (14)	C15—C14—H14	119.7
C1—N1—C20	117.20 (16)	C13—C14—H14	119.7
C5—N1—C20	120.27 (15)	C14—C15—C16	119.7 (2)
C4—C5—N1	119.75 (16)	C14—C15—H15	120.2
C4—C5—C12	122.43 (16)	C16—C15—H15	120.2
N1—C5—C12	117.83 (14)	C15—C16—C17	120.35 (19)
C5—C4—C3	121.28 (16)	C15—C16—H16	119.8
C5—C4—H4	119.4	C17—C16—H16	119.8
C3—C4—H4	119.4	C16—C17—C12	120.56 (18)
C4—C3—C6	115.00 (14)	C16—C17—H17	119.7
C4—C3—C2	107.90 (13)	C12—C17—H17	119.7
C6—C3—C2	113.52 (13)	C11—C6—C7	117.76 (16)
C4—C3—H3	106.6	C11—C6—C3	119.83 (16)
C6—C3—H3	106.6	C7—C6—C3	122.41 (15)
C2—C3—H3	106.6	C6—C7—C8	120.64 (16)
C18—C2—C19	109.14 (16)	C6—C7—H7	119.7
C18—C2—C1	107.56 (15)	C8—C7—H7	119.7
C19—C2—C1	109.21 (15)	C9—C8—C7	120.66 (18)
C18—C2—C3	110.55 (14)	C9—C8—H8	119.7
C19—C2—C3	112.75 (16)	C7—C8—H8	119.7
C1—C2—C3	107.49 (13)	C8—C9—C10	119.31 (18)
O1—C1—N1	122.78 (18)	C8—C9—H9	120.3
O1—C1—C2	120.61 (18)	C10—C9—H9	120.3
N1—C1—C2	116.61 (15)	C9—C10—C11	120.10 (18)
N1—C20—H20A	109.5	C9—C10—H10	119.9
N1—C20—H20B	109.5	C11—C10—H10	119.9
H20A—C20—H20B	109.5	C10—C11—C6	121.49 (19)
N1—C20—H20C	109.5	C10—C11—H11	119.3
H20A—C20—H20C	109.5	C6—C11—H11	119.3
H20B—C20—H20C	109.5	N2—C18—C2	177.8 (2)
C17—C12—C13	118.25 (17)	C2—C19—H19A	109.5
C17—C12—C5	119.38 (15)	C2—C19—H19B	109.5
C13—C12—C5	122.30 (16)	H19A—C19—H19B	109.5
C14—C13—C12	120.59 (19)	C2—C19—H19C	109.5
C14—C13—H13	119.7	H19A—C19—H19C	109.5
C12—C13—H13	119.7	H19B—C19—H19C	109.5
C15—C14—C13	120.6 (2)
C1—N1—C5—C4	17.3 (3)	C4—C5—C12—C13	−126.4 (2)
C20—N1—C5—C4	−153.18 (18)	N1—C5—C12—C13	53.8 (2)
C1—N1—C5—C12	−162.90 (16)	C17—C12—C13—C14	−0.6 (3)
C20—N1—C5—C12	26.7 (2)	C5—C12—C13—C14	176.27 (19)
N1—C5—C4—C3	1.8 (2)	C12—C13—C14—C15	−0.4 (3)
C12—C5—C4—C3	−178.07 (14)	C13—C14—C15—C16	0.9 (3)
C5—C4—C3—C6	−166.41 (16)	C14—C15—C16—C17	−0.3 (3)
C5—C4—C3—C2	−38.6 (2)	C15—C16—C17—C12	−0.7 (3)
C4—C3—C2—C18	−62.22 (18)	C13—C12—C17—C16	1.1 (3)
C6—C3—C2—C18	66.46 (19)	C5—C12—C17—C16	−175.85 (16)
C4—C3—C2—C19	175.31 (15)	C4—C3—C6—C11	−137.37 (18)
C6—C3—C2—C19	−56.0 (2)	C2—C3—C6—C11	97.7 (2)
C4—C3—C2—C1	54.90 (18)	C4—C3—C6—C7	42.6 (2)
C6—C3—C2—C1	−176.42 (14)	C2—C3—C6—C7	−82.3 (2)
C5—N1—C1—O1	−174.80 (19)	C11—C6—C7—C8	−1.7 (3)
C20—N1—C1—O1	−4.1 (3)	C3—C6—C7—C8	178.33 (16)
C5—N1—C1—C2	5.1 (3)	C6—C7—C8—C9	0.2 (3)
C20—N1—C1—C2	175.85 (17)	C7—C8—C9—C10	1.5 (3)
C18—C2—C1—O1	−102.1 (2)	C8—C9—C10—C11	−1.7 (4)
C19—C2—C1—O1	16.2 (3)	C9—C10—C11—C6	0.1 (4)
C3—C2—C1—O1	138.8 (2)	C7—C6—C11—C10	1.5 (3)
C18—C2—C1—N1	77.9 (2)	C3—C6—C11—C10	−178.5 (2)
C19—C2—C1—N1	−163.74 (18)	C19—C2—C18—N2	−12 (6)
C3—C2—C1—N1	−41.1 (2)	C1—C2—C18—N2	107 (6)
C4—C5—C12—C17	50.4 (2)	C3—C2—C18—N2	−136 (6)
N1—C5—C12—C17	−129.39 (17)