O. P. Demidov

Heterocyclic Analogs of Pleiadene. 71. Synthesis of 1,3-Diazapyrene

The reaction of perimidine and 2-R-perimidines with α,β-unsaturated carbonyl compounds in polyphosphoric acid has yielded the previously unknown 1,3-diazapyrene and its 6,8-di- and also 2,6,8-trisubstituted derivatives. Their spectroscopic parameters are discussed.

Acid hydrolysis of amines and cleavage of 1,3,7-triazapyrene ethers

Acid hydrolysis of 6-amino derivatives of 1,3,7-triazapyrene affords the corresponding 6-oxo-6,7-dihydro-1,3,7-triazapyrenes. In the case of 6,8-bis(dialkylamino)-1,3,7-triazapyrenes depending on their structure products of hydrolysis of one or two dialkylamino groups are obtained. 6-Alkoxy-8-dialkylamino-1,3,7-triazapyrenes were synthesized. Conditions were found providing a possibility to cleave an ether bonds in the presence of amino group in the 1,3,7-triazapyrene structure and also to perform the hydrolytic substitution of both functional groups.

Direct oxidative SNH amidation of 1,3,7-triazapyrene

6-Acylamino-1,3,7-triazapyrenes have been synthesized for the first time by direct oxidative nucleophilic substitution of hydrogen.

Heterocyclic analogs of pleiadiene. 70. Synthesis of 6-hydroxy-1,3-diazapyrenes

The regioselectivity of the reactions of perimidine with cinnamic acids in polyphosphoric acid (PPA) depends on the P2O5 content. Procedures were developed for the synthesis of 4(9)- and 6(7)-cinnamoylperimidines. Cyclization of the latter under the action of an excess of AlBr3 was accompanied by dearylation to form 6-hydroxy-1,3-diazapyrene.

Amides of 1,3,7-triazapyrene series: synthesis by nucleophilic substitution of alkoxy groups

The treatment of 6,8-dialkoxy-1,3,7-triazapyrenes with sodium acylamides in DMSO at room temperature resulted in ipso substitution of one alkoxy group with amide group, giving 8-acylamino-6-alkoxy-1,3,7-triazapyrenes. The reaction at 65–70°C proceeded as a tandem SNAripso–SN2 process, leading to the formation of 8-acylamino-6-oxo-6,7-dihydro-1,3,7-triazapyrenes.

1,3,7-Triazapyrene: the first case of hetarylation of benzene and its analogs

The reactions of heteroaromatic cations with neutral aromatic compounds is an important method for the introduction of heterocyclic substituents into the molecules of organic compounds. Depending on the nature of the substrate, similar processes are known as electrophilic hetarylation of arenes or nucleophilic arylation of hetarenes; such reactions are well known for various azines [1-5]. Generally azaheterocycles are activated by N-acylation, N-protonation, or N-alkylation, but π-rich arenes or hetarenes (phenols, arylamines, their O- and N-alkyl derivatives, pyrrole, indole, etc.) are used as the aromatic reagents. This process has found use for the construction of new heterocyclic systems [6, 7]. During a study of the nucleophilic substitution of hydrogen in a series of 1,3,7-triazapyrenes [8-11] we observed a reaction unusual for azines, namely, arylation by benzene and its homologs. The reaction occurred in a polyphosphoric acid (PPA) medium containing 86% P2O5 [12]. The reaction of 1,3,7-triazapyrene (1) with a large excess of benzene occurred at the boiling point of the latter, and in the case of toluene or o-xylene at 100-110°C. The process was accompanied by the development of a deep red coloration that is characteristic of the dihydrotriazapyrene structure. However, we were unable to isolate the intermediate products resulting from the nucleophilic addition of arenes – the σ-adducts 2a-c – since on alkalinization they underwent oxidative dehydroaromatization in the presence of air oxygen with the formation of 6-phenyl- (3a), 6-p-tolyl- (3b), and 6-(3,4-dimethylphenyl)-1,3,7-triazapyrene (3c), respectively.

SNH Arylation of 1,3,7-triazapyrenes in acidic aqueous solution

The reaction of 1,3,7-triazapyrenes with π-electron rich arenes in concentrated hydrochloric acid yielded the corresponding 6-aryl-1,3,7-triazapyrenes. An example of double arylation of 1,3,7-triaza-pyrene was found.

SYNTHESIS AND CLEAVAGE OF 1,3,7-TRIAZAPYRENE ETHERS

Oxidative alkoxylation of 1,3,7-triazapyrenes in the system ROH–H2O–KOH–K3Fe(CN)6 leads via a tandem SNH–SNH process to the formation of 6,8-dialkoxy-1,3,7-triazapyrenes. Hydrolytic cleavage of these ethers leads to products of single or double dealkylation, depending on the reaction conditions.

Oxidative SNH amidation of acridine and tautomerism of N-(acridin-9-yl)benzamides

Direct oxidative nucleophilic substitution of hydrogen atom in acridine molecule was used to synthesize 9-acylaminoacridines. The prototropic amine-imine tautomerism of these compounds was studied.

Urea in an aminodemethoxylation reaction of 6-methoxy-1,3,7-triazapyrenes

Upon reaction of N-anion of urea with 6-methoxy-1,3,7-triazapyrenes in DMSO at room temperature the products of nucleophilic ipso substitution of methoxy group with amino group form in high yields.