Chemistry of Heterocyclic Compounds, Vol. 37, No. 4, 2001
CYCLOCONDENSATION
AND AROMATIZATION DURING
REACTION OF DIMEDONE,
p-DIMETHYLAMINOBENZALDEHYDE,
AND AMMONIUM ACETATE
I. B. Dzvinchuk and N. A. Tolmacheva
Keywords: acridines, aldehydes, aromatization, cleavage, cyclocondensation, Hansch reaction.
Information about products of three-component cyclocondensation of dimedone 1,
p-dimethylaminobenzaldehyde 2, and ammonium acetate 3 is contradictory. According to [1], when boiled in
acetic acid they form the decahydroacridine derivative 4, and "in some cases" a colorless substance which is
assigned the structure of octahydroacridine 5. Formation of the second product is explained by the fact that
compound 4 "is easily oxidized by oxygen in the air or disproportionates". However, according to data in [2],
compound 4 is stable in DMSO at 120°C for 6 h. It was synthesized under these conditions, and no
aromatization products are mentioned (Scheme 1).
We have acquired new facts pertaining to reaction of reagents 1-3. When they are boiled in ethanol, the
formation of compound 4 proceeds selectively. The yield is 90% (according to the method in [1,2], the yield is
respectively 56% and 51%). When they are boiled in acetic acid, the reaction does not stop at the stage of
formation of product 4, but also does not lead to compound 5. Subsequent aromatization, as we have
established, occurs with cleavage of N,N-dimethylaniline (detected by TLC) and results in the derivative of
octahydroacridine 6 in 85% yield. The latter is obtained more rapidly and in purer form when compound 4 is
boiled in acetic acid. The same product is obtained [1] by oxidation of decahydroacridine 7 by nitrous acid, and
we have duplicated this synthesis. Samples obtained by the three methods are identical according to
TLC data, and mixed samples do not result in depression of the melting point. The structure of compound 6, and
in particular the absence of a p-dimethylaminophenyl moiety in it, is confirmed by physical and chemical
studies.
Thus the condensation products of aldehyde 2 tend toward cleavage of N,N-dimethylaniline. The
phenomenon we observed probably can be used in practical organic synthesis. Favorable factors for this include
the accessibility, stability during storage, safety, and easy measurement of quantities of the reagent 2 used. The
example we have proposed can be considered as a novel approach to Hansch type synthesis of pyridines, making
it possible to construct a γ-unsubstituted pyridine ring, without using an oxidizing agent, according to a simple
and very effective procedure.
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Institute of Organic Chemistry, National Academy of sciences of Ukraine, Kiev 02094; e-mail:
iochkiev@ukrpack.net. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 554-555, April, 2001.
Original article submitted December 7, 2000.
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0009-3122/01/3704-0506$25.00©2001 Plenum Publishing Corporation