Preparation of Pyridyl-substituted Monoazatriphenylenes

Abstract

Azatriphenylene derivatives are of considerable interest due to their promising photophysical and coordinating properties [1] and to their presence in the composition of natural compounds [2,3]. Azatriphenylenes are important in inorganic biochemistry thanks to their use as intercalating ligands [4,5]. In addition, azatriphenylenes have shown promise as luminescent chemosensors of organic anions and nitroaromatic compounds [6].The most frequently used method for preparing azatriphenylenes is the Skraup synthesis [7,8] which demands the use of forcing conditions. Contemporary synthetic methods broadly use a cycloaddition reaction of hard to obtain alkenes or arylacetylenes with aromatic substrates catalyzed by transition metal salts [9,10]. Finally, the cyclocondensation of phenanthrenequinone with hydrazones of (hetero)aromatic carboxylic acid amides leads to the corresponding aryl- [11,12] and hetaryl-substituted [13] triazatriphenylenes.In this report, we propose an efficient method for the synthesis of cycloalkene-annelated derivatives of monoazatriphenylenes based on an aza-Diels-Alder reaction of the previously uncharacterized 3-(pyridin-2-yl)phenathro[9,10-e][1,2,4]triazine (1) [14] with 1-morpholinocycloalkenes. A method for preparing different pyridine derivatives through reaction of the corresponding mononuclear 1,2,4-triazines has been known for some time [15][16][17]. In our work, we have used this method for the first time in a single-stage synthesis of the poorly available pyridyl-substituted monoazatriphenylenes 2a,b.

Synthesis and characterizations of new cadmium complexes based on poly(aza)arene-annelated 2,2′-bipyridines

“…weaker) than a typical Cd-N bond length: the Cd-N distances are from 2.427(5) Å in complex 1 to 2.491(5) Å in complex 2 and 2.481(7) in complex 3. In addition the conjugation between pyridyl and isoquinolinyl or monoazatriphenylenyl moieties of the ligand in the Cd(II) coordination node is violated: the twist angle values are 38.8(5)°in complex 1, 37.7 (6)°in complex 2, and 37.4(5)°or 38.9(6)°in complex 3, which is different from the twist angle values reported for Cd(II) 2,2 0 -bipyridine complexes [14], typically from 0.5°to 22° [15,16]. These differences in the values of geometric characteristics for complexes 1-3 can be explained first of all by the steric repulsion between the benzene-or cyclopentane-anneleted pyridine moieties and the non-anneleted pyridine ring in the Cd(II) complexes 1-3.…”

“…The ligands used for the preparation of cadmium complexes were synthesized according to the previously reported [13,14] ''1,2,4-triazine" methodology (Scheme 1). Thus, the aza-DielsAlder reaction between 1,2,4-triazines and 1-morpholinocycloalkenes allows to obtain corresponding cycloalkene-annelated 2,2 0 -bipyridine ligands.…”

Cycloaddition Reactions of Enamines

“…[95] An efficient method for the synthesis of cycloalkeneannulated derivatives of monoazatriphenylenes based on an aza-Diels-Alder reaction of triazine 274 with 1-morpholinocycloalkenes was presented by D. S. Kopchuk. [96] The monoazatriphenylenes 275 a,b were prepared by heating compound 274 in the presence of a fivefold excess of the corresponding cyclic enamine at 200 °C without solvent with the yield 78 % and 68 % respectively (Scheme 94).…”

Mono‐ and Polyazatriphenylene‐Based Ligands: An Updated Library of Synthetic Strategies (2001–2018)

“…Recently, we developed an efficient method for the synthesis of cycloalkene‐anellated derivatives of monoazatriphenylenes based on an aza‐Diels–Alder reaction of 3‐(pyridin‐2‐yl)phenanthro[9,10‐ e ][1,2,4]triazine ( 129 ) with 1‐morpholinocycloalkenes ( 130 ) (Scheme ) . For the preparation of compounds 131a , b , we synthesized the corresponding triazatriphenylene 129 by direct heating of phenanthrenequinone 7 with the pyridine‐2‐carboxylic acid amide hydrazone ( 128 ).…”