1-(1-Hydr­oxy-9H-carbazol-2-yl)-3-methyl­but-2-en-1-one

Matthias Zeller; Makuteswaran Sridharan; Karnam J Rajendra Prasad; Aimable Ngendahimana

doi:10.1107/S1600536810000322

. 2010 Jan 9;66(Pt 2):o297–o298. doi: 10.1107/S1600536810000322

1-(1-Hydroxy-9H-carbazol-2-yl)-3-methylbut-2-en-1-one

Matthias Zeller ^a,^*, Makuteswaran Sridharan ^b, Karnam J Rajendra Prasad ^b, Aimable Ngendahimana ^a

PMCID: PMC2979736 PMID: 21579731

Abstract

The title compound, C₁₇H₁₅NO₂, was prepared as one of two products of the AlCl₃/POCl₃-catalysed reaction of 9-carbazol-1-ol with 3,3-dimethyacrylic acid. It crystallizes with two crystallographically independent molecules, A and B, which are virtually superimposable but not related by any translational or other pseudosymmetry. Both independent molecules are almost planar [r.m.s. deviations from planarity = 0.053 (1) and 0.079 (1) Å in A and B, respectively] and contain an intramolecular O—H⋯O hydrogen bond. Each type of molecules is connected via pairs of N—H⋯O hydrogen bonds, forming centrosymmetric A ₂ and B ₂ dimers which are, in turn, arranged in offset π-stacks extending along the a-axis direction. The offset of the dimers and the tilt angle of the molecules allows the formation of alternating C—H⋯π interactions between A and B molecules of parallel stacks.

Related literature

For synthetic strategies for the synthesis of carbazole and its derivatives, see: Chakraborty (1993 ▶). For the isolation of pyranocarbazoles from various plant species, see: Knölker & Reddy (2002 ▶, and references therein). For the synthesis of related compounds, see: Kavitha & Rajendra Prasad (2003a ▶,b ▶); Patel (1982 ▶). For the structure of the second product of the reaction yielding the title compound, see: Sridharan et al. (2008 ▶).

Experimental

Crystal data

C₁₇H₁₅NO₂
M _r = 265.30
Triclinic,
a = 6.3416 (9) Å
b = 15.202 (2) Å
c = 15.462 (3) Å
α = 115.216 (5)°
β = 95.042 (5)°
γ = 101.922 (4)°
V = 1293.2 (4) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 100 K
0.31 × 0.19 × 0.16 mm

Data collection

Bruker SMART APEX CCD diffractometer
Absorption correction: multi-scan (APEX2; Bruker, 2007 ▶) T _min = 0.749, T _max = 0.986
13387 measured reflections
6364 independent reflections
4788 reflections with I > 2σ(I)
R _int = 0.026

Refinement

R[F ² > 2σ(F ²)] = 0.048
wR(F ²) = 0.123
S = 1.01
6364 reflections
367 parameters
H-atom parameters constrained
Δρ_max = 0.35 e Å⁻³
Δρ_min = −0.25 e Å⁻³

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL and Mercury (Macrae et al., 2008 ▶); software used to prepare material for publication: SHELXTL, PLATON (Spek, 2009 ▶) and publCIF (McMahon & Westrip, 2008 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810000322/bv2136sup1.cif

e-66-0o297-sup1.cif^{(27.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810000322/bv2136Isup2.hkl

e-66-0o297-Isup2.hkl^{(311.5KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

Cg1, Cg2 and Cg3 are the centroids of the phenyl rings C1B–C6B, C7A–C12A and C1A–C6A, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1B—H1D⋯O2B	0.84	1.73	2.4762 (16)	146
O1A—H1C⋯O2A	0.84	1.72	2.4626 (16)	146
N1B—H1B⋯O1Bⁱ	0.88	2.12	2.9561 (17)	157
N1A—H1A⋯O1Aⁱⁱ	0.88	2.08	2.8996 (16)	155
C10A—H10A⋯Cg1ⁱⁱⁱ	0.95	2.66	3.365 (2)	132
C10B—H10B⋯Cg2ⁱⁱ	0.95	2.68	3.427 (2)	136
C16A—H16A⋯Cg3ⁱⁱⁱ	0.95	2.77	3.659 (2)	152
C16B—H16D⋯Cg1^iv	0.95	2.96	3.846 (2)	151

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) .

Acknowledgments

We acknowledge the UGC, New Delhi, India, for the award of Major Research Project grant No. F. 31–122/2005. MS thanks the UGC, New Delhi, for the award of a research fellowship. The diffractometer was funded by NSF grant No. 0087210, by Ohio Board of Regents grant CAP-491 and by YSU.

supplementary crystallographic information

Comment

A number of carbazole alkaloids with intriguing novel structures and useful biological activities were isolated from natural sources over the past decades, which led towards the development of new synthetic strategies for the synthesis of carbazole and its derivatives (Chakraborty, 1993). Among the physiologically active carbazoles found aree pyranocarbazole alkaloids, which have a C-13, C-18 or C-23 framework (Knölker & Reddy, 2002). The basic unit is the C-12 carbazole nucleus with one carbon attached as a methyl, formyl, carboxylic or ester group. This C-13 unit then leads to C-18 or C-23 carbazole alkaloids depending on whether it combines with a hemi-terpenoid or a mono-terpenoid unit. Another observation is that in all the pyranocarbazole derivatives isolated so far, the oxygen atom of the pyran ring is attached to carbon-2 of the carbazole nucleus to form essentially pyrano[3,2-a]carbazole as in grinimbine. Patel (1982, and references therein) has reported the synthesis of indolo[3,2-h]chromanones from 1-hydroxycarbazoles which were then converted to isomers of grinimbine. Here the yields of compound were reported to be moderate since it was obtained along with the respective 2-acryloyl-1-hydroxycarbazole.

In this context we aimed to prepare pyrano[2,3-a]carbazoles using 1-hydroxycarbazoles as starting synthons under various reaction conditions (Kavitha & Rajendra Prasad, 2003a,b, and references therein). Using the catalyst mixture AlCl₃/POCl₃ along with 9-carbazole-1-ol and 3,3-dimethyacrylic acid as the reactants we obatined a mixture of two products i.e., 1-(1-hydroxy-9H-carbazol-2-yl)-3-methylbutan-1-one and 2,2-dimethyl-2,3-dihydropyrano-[2,3-a]carbazol- 4(11H)-one as described in an earlier publication (Sridharan et al., 2008) and in Figure 1. The structure of the cyclized compound 2,2-dimethyl-2,3-dihydropyrano-[2,3-a]carbazol- 4(11H)-one was described in the earlier structure report (Sridharan et al., 2008). Here we would like to present the structure of the second compound isolated, 1-(1-hydroxy-9H-carbazol-2-yl)-3-methylbutan-1-one.

The title compound crystallizes in a triclinic setting with two crystallographically independent molecules, A and B (Figure 2). The two molecules are virtually superimposable (see overlay of the two structures in Figure 3) but a PLATON symmetry check did not reveal any translational or other pseudosymmetry even when using relaxed tolerances (Spek, 2009). Both independent molecules are planar, r.m.s. deviations from planarity are 0.053 and 0.079 Å², respectively, and they are tilted against each other within the structure with a dihedral angle of the planes of the A and B molecules of 53.11 (2)°.

Each molecule exhibits a strong intramolecular O—H···O hydrogen bond between the phenolic hydroxyl group and the keto oxgen atom (Table 1). In addition each type of molecules is connected via pairs of N—H···O hydrogen bonds to another molecule of the same type to form centrosymmetric A₂ and B₂dimers (the planes of the dimers are parallel but slightly shifted against each other, Figure 4). The dimers are in turn arranged in offset π-stacks that are extending along the a axis direction. The metrics of the interaction are best given for the interaction of the phenol rings C7A to C12A and C7B to C12B with their respective symmetry equivalent counterparts at 2 - x, -y, 1 - z and 1 - x, -y, 2 - z. For these the centroid to centroid distances are 4.083 (1) and 4.089 (1) Å, the interplanar distances are 3.2985 (6) and 3.2992 (7) Å, and the slippages are 2.407 and 2.415 Å, respectively. The offset of the dimers and the tilt angle of the molecules allows for the formation of alternating C—H···π interactions between A and B molecules of parallel stacks. C—H···π interactions are given in Table 1, with ring centroids 1, 2 and 3 being the phenyl rings C1B to C6B, C7A to C12A and C1A to C6A, respectively.

Experimental

The title compound was synthesized as described previously by Sridharan et al. (2008): 9-Carbazole-1-ol (0.001 mol) and 3,3-dimethylacrylic acid (0.001 mol) were dissolved in the mixture of an ice-cold solution of AlCl₃/POCl₃ (400 mg/ 6 ml) and kept at room temperature for 24 h. The reaction process as monitored by TLC indicated the formation of two compounds. After completion of the reaction (disappearance of starting material), the residue was poured onto ice water. The solid separated out was filtered, dried and then separated by column chromatography on silica gel using petroleum ether/ ethyl acetate (98:2) as eluents to yield the title compound 1-(1-hydroxy-9H-carbazol-2-yl)-3-methylbutan-1-one and 2,2-dimethyl-2,3-dihydropyrano[2,3-a]carbazol-4(11H)-one, respectively as yellow prisms (Figure 1). The title compound was recrystallized from ethanol. Yield: 0.114 g (43%), m.p. 482- 484 K (209 - 211°C).