UNUSUAL PRODUCTS OF THE REACTION OF CARBAZOLE WITH ACETALDEHYDE AND PROPYNAL

E. E. Sirotkina, V. D. Filimonov, V. A. Anfinogenov

It is known that the reaction of secondary amines with aldehydes leads to aminals or to the corresponding enamines /1/. However, it turned out that in the reaction of carbazole with acetaldehyde in the presence of \(\mathrm{CaCl_2}\) or catalytic amounts of \(\mathrm{HCl}\) and \(\mathrm{H_2SO_4}\), neither an aminal nor 9-vinylcarbazole is formed; instead, compound IIIa, not described in the literature, is obtained in yields of up to 70%. The reaction proceeds analogously with propynal, with formation of IIIб. The structure of these compounds was established by IR and PMR spectroscopy (for spectral parameters see the experimental part). It was shown that the synthesized compounds III are hydrolyzed in an acidic medium with formation of carbazole and the corresponding aldehydes, which were isolated in the form of hydrazones.

The following scheme for the formation of III may be proposed:

\[ \begin{aligned} & R{-}CH_2{-}CH{=}O \xrightarrow{+H^+} RCH_2{-}\overset{+}{C}H{-}OH \xrightarrow[\,-H^+\,]{HNR_2} RCH_2{-}CH(OH){-}NR_2 + H^+ \\ & \longrightarrow RCH_2{-}\overset{+}{C}H{-}NR_2 + H_2O \\ & I + II \longrightarrow RCH_2{-}CH(NR_2){-}O{-}CH(NR_2){-}CH_2R,\quad 2d \\ & \hspace{4.5cm} III \\ & HNR_2 = \text{carbazole};\qquad IIIa\ R=H;\qquad IIIб\ R=CH_3 \end{aligned} \]

— aminosulfites of type I are very unstable and usually dehydrate in an acidic medium with intermediate formation of carbonium-ammonium ions of type II, which can either be attacked by the next molecule of amine, being converted into aminals, or eliminate a proton to give enamines /2/. However, up to now the subjects of investigation have mainly been strongly basic amines, whereas carbazole, possessing very low basicity /3/, is comparatively inactive in attacking II, which probably leads to alternative intermolecular dehydration of I with formation of III. Confirmation of the possibility of intermolecular dehydration of aminosulfites of type I is the ability of 9-oxymethylcarbazo-

to give, in an acidic medium, 9,9-dicarbazolyldimethyl ether /4/.

Experimental Part

$\alpha,\alpha'$-(9,9-dicarbazolyl)diethyl ether (IIIa). At 65–70°C, 10 g (0.06 mole) of carbazole, 5 g of CaCl$_2$, and 6.8 ml (0.12 mole) of acetaldehyde in 50 ml of benzene are stirred; after 2 hours the reaction mixture is cooled and filtered. The filtrate is evaporated by 2/3; ethanol is added to the residue until turbidity appears, and on standing 5.6 g (60%) of product crystallizes in the form of small white needles; m.p. after repeated recrystallization from a benzene–ethanol mixture 191–191.5°. The substance is readily soluble in benzene, CCl$_4$, acetone, and ether, and poorly soluble in alcohols. Found: C 83.51; H 6.15; N 6.78; O 3.56%. C$_{28}$H$_{24}$N$_2$O. Calculated: C 83.17; H 5.96; N 6.93; O 3.94%. IR spectrum: intense band at 1084 cm$^{-1}$, C–O–C group; the band of the N–H group is absent; bands at 734 and 703 cm$^{-1}$ indicate a carbazole derivative unsubstituted in the nucleus. PMR spectrum: d. CH$_3$ 8.4 ppm ($J$ 6 Hz, 6 H), q. CH 4.36 ppm ($J$ 6 Hz, 2 H), m. aromatics 2.8 ppm (16 H).

$\alpha,\alpha'$-(9,9-dicarbazolyl)dipropyl ether (IIIb) was obtained from propionaldehyde and carbazole analogously to IIIa in 56% yield in 2.5 hours. Colorless prismatic crystals with m.p. 175–175.5° from a benzene–ethanol mixture. Found: N 6.5%. C$_{30}$H$_{28}$N$_2$O. Calculated: 6.48%. The IR spectrum is analogous to the spectrum of IIIa. PMR spectrum: t. CH$_3$ 9.5 ppm ($J$ 6 Hz, 6 H), m. CH$_2$ 7.84 ppm (4 H), t. CH 4.56 ppm ($J$ 6 Hz, 2 H), m. aromatics 2.8 ppm (16 H).

Analogously to IIIa and IIIb, with yields of 50–70% when using 1–2 wt.% relative to carbazole, hydrochloric and sulfuric acids were obtained.

The IR spectra of the substances in KBr pellets were recorded on an IKS-14 instrument. The PMR spectra were recorded on a BS 487C instrument at a frequency of 80 MHz, 10% solutions in CCl$_4$, internal standard HMDS; the chemical shifts are given on the $\tau$ scale.

Literature

1. Weygand–Hilgetag. Methods of Experiment in Organic Chemistry, Moscow, “Khimiya,” 470, 1968.

2. J. R. Dyer. Collected volume, Modern Problems of Physical Organic

chemical chemistry.” Moscow, “Mir,” 342, 1967.
3. H. Y. Chen, L. E. Hakka, R. L. Minnan, A. Y. Kresge, E. B. Whipple, J. Am. Chem. Soc., 93, 5102, 1971.
4. V. F. Traven’, V. A. Smrchek, B. I. Stepanova. KhGS, 568, 1967.

REARRANGEMENT OF \(N\)-ACETYLDIPHENYLAMINE

E. E. Sirotkina, R. M. Kogan

The Fries–Rosemund rearrangement, as a convenient preparative method for the synthesis of aliphatic–aromatic ketones as applied to derivatives of diarylamines, did not give positive results. In the rearrangement of \(N\)-substituted diarylamines, the ortho derivatives formed either cyclize to the corresponding acridines /1/ or, as in the case of \(N\)-acetyldiphenylamine, the rearrangement does not take place even in the presence of such active catalysts as aluminum chloride and polyphosphoric acid /2, 3/.

We investigated the rearrangement of \(N\)-acetyldiphenylamine in the presence of equimolecular amounts of aluminum chloride and hydrogen chloride in various organic solvents at different temperatures and reaction times. In all cases studied, an intermolecular rearrangement is observed, with formation of diacetyldiphenylamine and diphenylamine. Among the solvents studied (nitrobenzene, nitromethane, chlorobenzene, methylene chloride), the last proved to be the best; the highest yield of diacetyldiphenylamine (30% of theoretical) is achieved after 30 min of reaction time at a temperature of 40–41°C. With an increase in reaction time, resinification of the products increases.

To clarify the donor activity of the heteroatoms of acetyl derivatives of diphenylamine, the IR spectra of complexes of \(N\)-acetyldiphenylamine and diacetyldiphenylamine with aluminum chloride were studied. In the spectra of the complexes, new absorption bands appear in the regions 1400–1700 cm\(^{-1}\) and 2900–3100 cm\(^{-1}\), indicating that both donor centers participate in complex formation. Upon addition of hydrogen chloride to the system, the intensity of the absorption band of the bound \(C=O\) group (1572 cm\(^{-1}\)) increases and the intensity of the absorption bands of the tre-