Condensation of dimedone with 1,2-dibenzovlethylene in the presence of base gave 2- (4,4-dimethyl-2,6-dioxocvclohe.wl)-l,4-diphenylbutane-l,4-dione. Its reaction with amines gives the corresponding pyrrole derivatives.An extremely promising basis for building up the pyrrolo[4,3,2-d,e]quinoline system (which appears in the structure of many natural alkaloids) are tetracarbonyl compounds in which two carbonyl groups are situated in 1,4 positions to one another and the other two in a 1,5 position. As a model compound we chose the Michael adduct d: dimedone with trans-3-benzoylacrylic acid. With this adduct the synthesis of the novel pyrrolo[4,3,2-d,e]quinoline structure was successfully carried out by use of ammonia [I].With the aim to explore the range for use of the given scheme we have carried out the synthesis of novel tetracarbonyl compounds by condensation of dimedone with trans-l,2-dibenzoylethylene and studied its reaction with N-nucleophiles. Reaction ofdimedone with 1,2-dibenzoylethylene proceeded in alcoholic solution in the presence of KOH.
+ Ph% KOH Ph EtOFIOl I / v \ l/ "Ph
HO 0 0Formation of compound l was confirmed by the presence of an AMX spin system (COCI-hCR2) in its PMR spectrum.We have carried out the reaction of tetraketone I with ammonia, methylamine, benzylamine, o-phenylenediamine, and aniline. The involvement of the dimedone fragment was assumed with the formation h ~ not of the pyrrolo[4,3,2-d,e]quinoline system II, then at least of a tetrahydroindole structure. However, in all cases, pyrrole derivatives were obtained.Reaction with ammonia, methylamine, and benzylamine in aqueous alcohol solution in an autoclave led to formation of compounds llla-c. Formation of the pyrroles llla-c was confirmed by the presence in their PMR spectra of 4-H pyrrole proton signals in the region 6.2-6.8 ppm and enamine fragment NH protons at 4.5-5.4 p~rn (as well as in the case of compound ilia the signal for the pyrrole NH proton at 8.5 ppm). IR absorption bands in the region 3400-3370 cm t are characteristic of NH stretching vibrations for the NH groups of the enamines. In the spectrum of compound Ilia there appears a band at 3270 cm t (pyrrole NH).
