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

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 diand trichloromethyl substituents react with alkoxide anions to give products of ring hydrogen substitution by an alkoxy group [1-4]. 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-alkoxyand 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 K3Fe(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.