Synthesis and cleavage of 1,3,7-triazapyrene ethers

Abstract

H -S N H alkoxylation.Classical strategies for the synthesis of ethers of nitrogen-containing heterocycles are based on the substitution of good leaving groups. Reactions proceeding by a tele-mechanism are among non-oxidative methods for obtaining such results. For example, heteroarenes with di-and trichloromethyl substituents react with alkoxide anions to give products of ring hydrogen substitution by an alkoxy group [1][2][3][4].In the case of electron-deficient aza-aromatic substrates, an excellent alternative may be direct oxidative nucleophilic substitution of hydrogen (ONSH [5]) by an alkoxy group, since it does not require a preliminary introduction of a good nucleofuge into the molecule. Yet we have found only two literature examples of successful heterocycle alkoxylation according to the ONSH process. Thus, the reaction of 1,3-dimethyllumazine with N-bromosuccinamide in the corresponding primary alcohol led to 6-alkoxy-and 6,7-dialkoxy derivatives of 1,3-dimethyllumazine [6]. Methoxylation of 2-nitro-5,10,15,20-tetraphenylporphyrin copper complex with sodium methoxide in DMF is reported in paper [7].Against this background, our previous observations of the easy ONSH alkoxylation [8,9], amination [10], and alkylamination [11] of 1,3,7-triazapyrenes is of great interest. Thus, the oxidative alkoxylation of 1,3,7-triazapyrene (1a) and its 2-methyl derivative 1b occurs at room temperature in the corresponding aqueous alcoholic solutions with an excess of KOH and K 3 Fe(CN) 6 [8], whereas compounds 1a and 1b remain unchanged in the conditions mentioned above [6]. With primary alcohols, the process results in the formation of previously unknown 6,8-dialkoxy derivatives of this heterocycle, 2a-d.The objective of the present work was a further investigation of this reaction, and also the possibility of hydrolytic cleavage of the ethers obtained.Allyl alcohol and ethylene glycol react with 1,3,7-triazapyrene (1a) under conditions used for the synthesis of compounds 2a-d, which allowed us to obtain also the 6,8-diallyloxy-(2e) and 6,8-bis(2-hydroxyethoxy)-1,3,7-triazapyrene (2f), respectively.

Synthesis of 2-Azapyrenes and Their Photophysical and Electrochemical Properties

“…This compound has been prepared by thermal cyclization, by using a lengthy nine step-sequence, by PPA (polyphosphoric acid)-induced Beckmann rearrangement, and by peri -annulation with sym -triazines . In the course of the development of Pd-catalyzed cross-coupling reactions, ,− a number of di- and triazapyrenes and related molecules have been published. ,− Recently, the group of Kozaki published an intramolecular Cu­(I)-catalyzed C–H functionalization approach, while Han et al applied the classical Bischler–Napieralski cyclization of amide precursors …”

Ureas as a New Nucleophilic Reagents for SNAr Amination and Carbamoyl Amination Reactions in 1,3,7‐Triazapyrene Series

“…Interestingly enough that the use of NaNH 2 instead of the urea anion in the reaction with compound 1a under same conditions resulted in the formation of known 8‐methoxy‐7 H ‐1,3,7‐triazapyren‐6‐one ( 8 ) in 85% yield (Scheme ). Undoubtedly, this is a product of the S N 2 process.…”

“…8‐Methoxy‐7 H ‐1,3,7‐triazapyren‐6‐one ( 8 ) was obtained as brown solid (107 mg, 85%), mp 215–216°C (EtOH), (Ref. mp 215–216°C).…”

1,3,7-Triazapyrene-Basedortho-Carborane Fluorophores: Convenient Synthesis, Theoretical Studies, and Aggregation-Induced Emission Properties

“…The reaction of 1,3,7-triazapyrene ( 3 ) with electron-rich arenes in concentrated hydrochloric acid yields a limited amount of 6-aryl-1,3,7-triazapyrenes (Scheme , route B) . Oxidative nucleophilic alkoxylation (Scheme , route C) and (alkyl)­amination (Scheme , routes D (S N H ) and E have also been examined to deliver C(6)-heterosubstituted 1,3,7-triazapyrenes. Interestingly, only the C(6)-regioisomer has been obtained for those examples.…”