Transformation of carbazole 9-propenoxide
Abstract Generated abstract
This study examines ring-opening additions to carbazole 9-propenoxide by hydrogen chloride, alcohols, and phenols under acidic or alkaline conditions. The products were prepared under monitored reaction conditions and characterized by melting points, elemental and hydroxyl analyses, thin-layer chromatography, IR data, PMR spectra, and, for the chlorohydrin, comparison of acylation rates with model primary and secondary alcohols. The results indicate that these transformations proceed with formation of secondary alcohols, including 1-chloro-3-(9-carbazolyl)propan-2-ol and a series of 1-alkoxy or 1-aryloxy-3-(9-carbazolyl)propan-2-ols. Identity of the phenoxy product was further supported by an independent synthesis from phenyl glycidyl ether and carbazole.
Full Text
TRANSFORMATIONS OF 9-PROPENOXIDE OF CARBAZOLE
I. P. Zherebtsov, V. P. Lopatinskii, N. M. Rovkina, F. S. Eliseeva
The aim of the present work is to study the nature of addition to the epoxide ring of carbazole 9-propenoxide by hydrogen chloride, alcohols, and phenols under conditions of electrophilic and nucleophilic catalysis.
A distinctive feature of the transformations studied is the formation exclusively of secondary alcohols both in the addition of hydrogen chloride and in the addition of alcohols and phenols.
The structure of 1-chloro-3-(9-carbazolyl)propan-2-ol /carbazole chloropropanol/, obtained by the action of hydrochloric acid on carbazole 9-propenoxide, as a secondary alcohol is proved by the PMR spectrum. A doublet with a chemical shift of 7.7 ppm corresponds to the signal of the protons in the fourth and fifth positions of the carbazole ring. The intensity of the multiplet with a chemical shift of 7.1 ppm makes it possible to assign it to the signal of the remaining six protons of the carbazole ring. The multiplet having a chemical shift of 3.7 ppm with an intensity corresponding to three protons should be assigned to the protons of the group \(N-CH_2-CH-\), bonded to the nitrogen of the heterocycle. The signal of the protons of the \(CH_2\) group bonded to chlorine has a chemical shift of 3 ppm and an intensity corresponding to two protons. According to literature data /1/, the chemical shift of the protons of the \(CH_2-Cl\) group is 3.3–3.6 ppm. (δ); for the \(-CH-Cl\) group (i.e., in the case of a primary chloropropanol), the proton signal would have a chemical shift of 3.9–4.1 ppm. The signal with a chemical shift of 2.15 ppm should apparently be assigned to the signal of the proton of the \(-OH\) group bonded to the \(-CH\) group. The signal of the proton of a hydroxide bonded to a \(CH_2\) group (in the case of a primary chloropropanol) should have the form of a triplet.
All the foregoing permits carbazole chloropropanol to be regarded as a secondary alcohol.
Table I presents the rate constants for the acylation of carbazole chloropropanol and of model alcohols: the primary alcohol, 9-(2-oxy)-
ethylcarbazole and secondary 9-(2-hydroxy)propylcarbazole with phthalic anhydride.
From the results presented it also follows that the chloropropanol obtained should be assigned to the secondary alcohols.
The interaction with alcohols and phenols was carried out in the presence of alkalis. The reaction with phenols was conducted in dioxane or acetone in the presence of potassium hydroxide. Alcohols added on boiling carbazole 9-propenoxide in an excess of alcohol in the presence of potassium hydroxide. The conditions of the transformation and the characteristics of the addition products are given in Tables 2 and 3, respectively.
As follows from the data of Table 3, the TLC results in various systems, and the IR-spectroscopic data, 1-(phenoxy)-3-(9-carbazolyl)propan-2-ol, obtained by direct interaction of carbazole 9-propenoxide with phenol and also by counter synthesis from phenyl glycidyl ether and carbazole, are identical. The structure of this product as a secondary alcohol follows from the NMR spectrum: a doublet at 7.88 ppm corresponds to the signal of two aromatic protons; the multiplet at 7.15 ppm should apparently be assigned to the remaining eleven aromatic protons. The signal at 4.32 ppm corresponds to three protons of the group \(N-CH_2-CH-\), and the doublet at 3.75 ppm to two protons of the group \(-CH_2-O-C_6H_5\). The signal at 2.07 ppm is assigned to one proton of the hydroxyl in the group \(-CH-OH\). In the case of a primary alcohol, a signal at 3.6 ppm would be present, with an intensity equal to one proton, in the form of a triplet or corresponding to three protons in the form of a multiplet /1/.
The other products of addition of phenols to carbazole 9-propenoxide have analogous spectra.
Thus, the products of addition of phenols to carbazole 9-propenoxide obtained by us are secondary alcohols.
The structure of the products of interaction of carbazole 9-propenoxide with alcohols also follows from the NMR spectra; these correspond to secondary alcohols. Thus, in the case of 1-(methoxy)-3-(9-carbazolyl)propan-2-ol, the doublet at 7.90 ppm corresponds to the signals of protons in the 4 and 5 positions of the carbazole ring. The low-intensity multiplet at 7.15 ppm can be assigned to the signal of the remaining six protons of the carbazole nucleus. The multiplet at 4.22 ppm, with an intensity corresponding to three protons, corresponds to the signal of the protons of the group \(N-CH_2-CH-\), bonded to the nitrogen of the heterocycle. The multiplet at 3.22 ppm, with an intensity [[unclear: continuation cut off at bottom of page]]
Table 1
Values of the rate constants for acylation of alcohols with phthalic anhydride
| Name of alcohol | \(k,\ \dfrac{\mathrm{L}}{\mathrm{mol}\cdot\mathrm{s}}\) |
|---|---|
| 9-(2-hydroxyethyl)carbazole | 0.00194 |
| 9-(2-hydroxypropyl)carbazole | 0.000662 |
| 1-chloro-3-(9-carbazolyl)propan-2-ol | 0.00103 |
Table 2
Results of experiments on the addition of hydrogen chloride, alcohols, and phenols to carbazole 9-propenoxide
| Ratio of reagents, mol | Addition conditions: introduced into the reaction, g | Addition conditions: medium | Addition conditions: temperature, °C | Addition conditions: duration, h | Yield, % of theoretical | Designation of addition products |
|---|---|---|---|---|---|---|
| A:B = 1:1.5 | A = 40 | acetone | 50 | 1 | 32.0 | I |
| A:V:G = 1:1:1 | A = 5 | dioxane | 106 | 21 | 35.0 | II |
| A:Zh:I = 1:1:1 | A = 5 | dimethyl sulfoxide | 25 | 45 | 31.0 | II |
| A:B:D = 1:1:1 | A = 5 | dioxane | 106 | 45 | 42.0 | III |
| A:V:E = 1:1:1 | A = 5 | acetone | 50 | 45 | 42.0 | IV |
| A:V = 1:1 | A = 5 | methanol | 65 | 2 | 54.0 | V |
| A:V = 1:1 | A = 4 | ethanol | 78 | 2 | 54.0 | VI |
| A:V = 1:1 | A = 5 | n-propanol | 97 | 2 | 57.0 | VII |
| A:V = 1:1 | A = 4 | n-butanol | 118 | 2 | 75.0 | VIII |
| I:K:B = 1.2:1:1 | K = 10.9 | acetone | 50 | 8 | 73.0 | II |
NOTE: A — carbazole 9-propenoxide; B — hydrochloric acid, \(d = 1.194\); V — potassium hydroxide; G — phenol; D — o-cresol; E — \(\beta\)-naphthol; Zh — lithium hydroxide monohydrate; I — phenylglycidyl ether; K — carbazole.
Table 3
Characteristics of the addition products
| Product designation | Product name | Melting point, °C | Solvent for recrystallization | Found, %: nitrogen content | Found, %: hydroxyl number by Berr | Empirical formula | Calculated, %: nitrogen content | Calculated, %: hydroxyl number |
|---|---|---|---|---|---|---|---|---|
| I | 1-chloro-3-(9-carbazolyl)propanol-2 | 67–68 | benzene:heptane = 1:1 | 5,4 | 6,35 | $C_{15}H_{14}OCl$ | 5,4 | 6,55 |
| II | 1-(phenoxy)-3-(9-carbazolyl)propanol-2 | 106,6 | cyclohexane | 4,2 | 5,42 | $C_{21}H_{19}O_2$ | 4,4 | 5,36 |
| III | 1-(ortho-toloxy)-3-(9-carbazolyl)propanol-2 | 80,4 | cyclohexane | 3,9 | 4,96 | $C_{22}H_{21}O_2$ | 4,2 | 5,14 |
| IV | 1-(α-naphthoxy)-3-(9-carbazolyl)propanol-2 | 120,6 | cyclohexane | 3,8 | 4,36 | $C_{25}H_{21}O_2$ | 3,8 | 4,60 |
| V | 1-methoxy-3-(9-carbazolyl)propanol-2 | 45,4 | petroleum ether | 5,3 | 6,82 | $C_{16}H_{17}O_2$ | 5,5 | 6,66 |
| VI | 1-(ethoxy)-3-(9-carbazolyl)propanol-2 | 49,4 | petroleum ether | 5,2 | 6,16 | $C_{17}H_{19}O_2$ | 5,2 | 6,31 |
| VII | 1-(n-propoxy)-3-(9-carbazolyl)propanol-2 | 63,4 | petroleum ether | 4,6 | 6,42 | $C_{18}H_{21}O_2$ | 4,9 | 6,01 |
| VIII | 1-(n-butoxy)-3-(9-carbazolyl)propanol-2 | 103,4 | cyclohexane | 5,1 | 6,06 | $C_{19}H_{23}O_2$ | 4,7 | 5,74 |
| I(*) | 1-(phenoxy)-3-(9-carbazolyl)propanol-2 | 106 | cyclohexane | 4,31 | 5,39 | $C_{21}H_{19}O_2$ | 4,4 | 5,36 |
*) Product obtained by counter synthesis.
the corresponding fifth proton, should be assigned to the signal of the protons of the group \(-CH_2-C-CH_3\). The chemical shift of the protons of the group \(-CH_2-O-CH_3\), according to literature data [1], is 3.3–3.6 ppm. In the case of a primary alcohol, the signal of the protons of the group \(-CH-O-CH_3\) would have a chemical shift of 3.5–4.1 ppm. And the signal at 2.2 ppm corresponds to the proton of the hydroxyl bound to the group \(CH(-CH-OH)\). The PMR spectrum of the primary alcohol would contain a signal from the proton of the primary hydroxyl group.
All of the above reveals the secondary character of the alcohols obtained (the PMR spectra of the addition products of other alcohols are analogous to the one discussed).
Experimental Part
The initial carbazole 9-propenoxide had a melting point of 108–109°, which agrees with [2].
To obtain carbazole chloropropanol, a mixture of carbazole 9-propenoxide with concentrated hydrochloric acid in acetone (200 ml) is boiled until the spot of carbazole 9-propenoxide disappears in a TLC sample (silica gel, benzene); the reaction mixture is poured into a tenfold volume of water, filtered, washed to neutral reaction, and recrystallized from a benzene:heptane mixture (1:1).
The addition of phenols to carbazole 9-propenoxide is carried out by boiling the reagents in a solvent or by keeping them at room temperature in the presence of alkali, with monitoring of the course of the process by TLC (silica gel, benzene:acetone 1:9). The products are isolated by the usual procedures.
The addition of alcohols is carried out analogously. Eluent for TLC: isooctane:ether 1:3.
The independent synthesis of phenoxycarbazolylpropanol is carried out by boiling, in 100 ml of acetone, a mixture of phenylglycidyl ether with carbazole and potassium hydroxide. The phenylglycidyl ether was obtained according to [3] and had the constants reported by the authors.
TLC was carried out on layers of KSM silica gel fixed with gypsum, in the ascending variant [4].
The PMR spectra were recorded on a BS 487C instrument in carbon tetrachloride at a temperature of 50° and a frequency of 80 MHz, with hexamethyldisiloxane as the internal standard. The signal positions are given on the \(\delta\) scale.
The kinetics of the interaction of the obtained chloropropanol and model alcohols with phthalic anhydride was studied at \(100^\circ\) in dry xylene at an initial phthalic anhydride concentration of 0.0366 mol/L, with the reagents in an equimolar ratio.
Freshly distilled phthalic anhydride was used. 9-(2-Hydroxy)ethylcarbazole and 9-(2-hydroxy)propylcarbazole were obtained according to [5] and [6], respectively, and had the melting points indicated by the authors.
References
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- I. M. Ezrielev, N. A. Larin. ZhOKh, 26, 791 (1956).
- A. M. Paquin, Epoxide Compounds and Epoxy Resins. Moscow, Goskhimizdat, 1962.
- A. A. Akhrem, A. I. Kuznetsova. Thin-Layer Chromatography. Moscow, “Nauka,” 1965.
- V. P. Lopatinskii, E. E. Sirotkina, I. P. Zherebtsov. Izvestiya TPI, 112, 42 (1963).
- E. E. Sirotkina, V. P. Lopatinskii. Author’s Certificate No. 182161; B.I. No. 11, 1966.
STUDIES IN THE CHEMISTRY OF CARBAZOLE DERIVATIVES.
INTERACTION OF CARBAZOLE 9-PROPENOXIDE WITH HYDROGEN CHLORIDE
I. P. Zherebtsov, V. P. Lopatinskii, N. M. Rovkina
In the interaction of hydrogen halides with unsymmetrical olefin oxides, the formation of halohydrins of both “normal” and “anomalous” structure is possible, which is associated both with the structure of the reacting oxide and with the reaction conditions [1].
We carried out the interaction of carbazole 9-propenoxide with hydrogen chloride (in the form of concentrated hydrochloric acid) in acetone and attempted to determine the nature of the chlorohydrin formed in this process. In accordance with the literature data, we expected the formation of