Nitrogen heterocyclic analogs of polyaryls

Abstract

Nitrogen heterocyclic analogs of polyaryls, derived from pyridine, quinoline, benzo[h]quinoline, indole, indolizine, and imidazo[l, 2-alpyridine, have been prepared from 1,4diacetyl-and 1,3,5-triacetylbenzene and 2,6-diacetylpyridine, for study of their physical, chemical and biological properties.Polyaryls a r e of interest as scintillators in liquid scintillation counters used in nuclear physics, and some of their heterocyclic analogs, especially 2,2'pphenylenebis( 5phenyloxazole) (POPOP) and its homologs, have also been employed with success for that purpose (1). In biology, one polyaryl, v i z . 1,3,5-tri-p-xenylbenzene (I), has been found to be carcinogenic, producing, on skin-painting in mice, not only epitheliomas in situ but also tumors of the liver (2); earlier, another polyaryl, 1,3,5-triphenylbenzene, had also been reported as carcinogenic (3) but this claim could not be confirmed later (4).Further, in our laboratory we are interested in investigating the behavior of polyaryls and their nitrogen heterocyclic analogs in Rayleigh light diffusion studies, as a means of determining electron delocalization in these molecules (5). These various interests led us to synthesize a number of nitrogencontaining analogs of polyaryls which include in their molecule the following heterocycles: pyridine, quino-The intermediates used were three polyketones:1 , 4diacetylbenzene, 1 , 3 , 5triacetylbenzene, and 2,6 -diacetylpyridine. In the indole group, 1,4diacetylbenzene, heated with phenylhydrazine, gave a bisphenylhydrazone which could be cyclized with either zinc chloride o r polyphosphoric acid to the pentacyclic 1,4-di-(2-indolyl)benzene (II); replacement of phenylhydrazine by pxenylhydrazine afforded the heptacyclic 1,4-di-(5-pheny1-2-indolyl)benzene (III). The bisphenylhydrazone and bis-ptolylhydrazone of 2,6-diacetylpyridine were cyclized by polyphosphoric acid to 2,6-di-(2-indolyl)pyridine ( N ) and 2,6-di-(5-methyl-2-indolyl)pyridine (V) respectively. Interestingly, these two compounds gave monopicrates with picric acid, which suggests that the heterocycle involved in this complex formation was the pyridine one rather than the indole one. 1,3,5-Triacetylbenzene readily gave trisarylhydrazones on heating a t 180' with phenyl-and p-tolylhydrazine, but not when the usual procedure for the preparation of hydrazones (use of arylhydrazine salts in ethanol) was employed; indolization, effected with polyphosphoric acid, furnished 1,3,5-tri-(2-indolyl)benzene (VI) and 1,3,5-tri-( 5 -methyl -2 -indoly1)benzene (VE) respectively. It is interesting to note that compound VI gave with tetrachlorophthalic anhydride a staale charge-transxx coinpiex (b) made up of three molecules of the electron acceptor for one molecule of the electron donor; this indicates that the three indole nuclei behave here as separate units in the charge-transfer phenomenon with the halogenated anhydride.In the quinoline series, a Pfitzinger reaction performed on one mole of 1,3,5-triacetylbenzene and 3 moles of isatin readily afforded "tri-atophan" (...

Unusual Product Distribution from Friedländer Reaction of Di- and Triacetylbenzenes with 3-Aminonaphthalene-2-carbaldehyde and Properties of New Benzo[g]quinoline-Derived Aza-aromatics

“…Introduction of BQ moiety to C 3 of the central benzene ring led to significant shift of H 2 of Ph by 0.76 ppm resonating at δ 9.12 as a one-proton triplet ( J = 0.8 Hz). In tri-substituted system 3e , H 2 of Ph was resonated at δ 9.30 as a three-proton singlet due to the two adjacent N 1 ’s of BQ moiety that is comparable to those of 1,3,5-tri(azaheteroar-2-yl)benzenes [28,30].…”

Synthesis of the Indole Ring

“…(Systems of the type Me N I II -CH-C-CH2seem to have been studied only in cyclic cases to date.) Recent work has brought to light several exceptions to these venerable generalizations (49,114,138,159,189). It now is clear that the direction of cyclization in a Fischer reaction may be highly dependent on the identity of the catalyst used and on the concentration of the catalyst.…”