The action of amines on 1,3,4-oxadiazolium salts

Abstract

1,3,4-0xadiazolium salts react with a wide variety of primary amines and ammonia to yield s-triazolium salts and s-triazoles, respectively; s-triazolo [I ,5-a] pyridinium salts and s-triazolo [1,5-a] pyridines are formed from 1,3,4-oxadiazolo[3.2-a] pyridinium perchlorates. Intermediate oxadiazolines or amidrazones resulting from attack of the amine a t C-2 of the oxadiazolium ring have been isolated from the reactions of triphenyloxadiazolium perchlorate with aniline, butylamine, secondary amines, and hydrazines. The subsequent fate of these intermediates depends on the nature of the amine and the conditions used.WE have recently described the synthesis of 1,3,4-When triphenyloxadiazolium perchlorate (1 a) is oxadiazolium salts (1) l p 2 and their conversion into heated with aniline in acetic acid the tetraphenyltri-N-aryl-s-triazolium salts (2) on treatment with primary azolium salt (2a) rapidly separates. The reaction was aromatic a m i n e ~. ~ This reaction resembles the form-extended to a wide range of oxadiazolium salts and ation of pyridinium salts from pyrylium salts and primary aromatic amines (see Table ) and at the time primary amines, a reaction that is widely applicable and constituted the first synthesis of lJ4-diaryl-1,2,4-trithat proceeds in both strongly and weakly basic media.4 azolium salts lacking functional groups.s Noteworthy Yield

Heterocyclische Carbene – Synthese und Koordinationschemie

“…Zunächst wurde ein geeignet substituiertes Oxazoliniumsalz synthetisiert. In Anlehnung an eine bekannte, aber ausbeuteschwache Synthese von N ‐Aryltriazoliumsalzen aus 1,3,4‐Oxadiazoliumsalzen59b gelang der Austausch des Sauerstoffatoms im Oxazolring durch Reaktion des Oxazoliumsalzes mit einem primären Amin. Das so erhaltene hydroxylierte Imidazolidiniumsalz eliminiert beim Erhitzen säurekatalysiert Wasser unter Bildung eines unsymmetrisch substituierten Imidazoliumsalzes vom Typ 15 .…”

An alternative approach to the synthesis of [1,2,4]triazolo[1,5‐a]pyridine‐8‐carbonitriles, their crystal structure, and DFT calculations

“…[10,15] [1,2,4]triazolo [1,5-a] pyridine-8-carbonitrile was prepared from 3- [1,2,4]triazolo [1,5-a]pyridine-8-yl-1,2,4-oxadiazole via the decomposition of oxazolyl moiety when heated to about 200 C (Scheme 1A). [11] 5,7-Dimethyl-2-alkyl(phenyl) [1,2,4]triazolo [1,5-a]pyridine-8-carbonitriles have been reported to obtain for the first time via the recyclization of oxadiazolopyridinium perchlorates when treated with NH 4 OH or NH 4 OAc (Scheme 1B) [16] and then upon cyclocondensation of 1-amino-4,6-dimethyl-2-oxo-1,2-dihydro-3-pyridinecarbonitrile with carboxamides in the presence of anhydrous ZnCl 2 (Scheme 1C). [12] Our work addresses the issue of construction of such compounds based on one-pot process from 2-(1H-1,-2,4-triazol-5-yl)acetonitriles and β-diketones or β-dialdehydes.…”

Synthetic Approaches to Chiral Non-C 2-symmetric N-Heterocyclic Carbene Precursors

“…75 The method developed by Boyd and Summers involves the conversion of the readily accessible alkyl-or arylhydrazines 209 into N,N′-diformylhydrazines 210 by treatment with the mixed anhydride of formic and acetic acid. 76 Subsequent condensation under acidic conditions (Ac 2 O and HClO 4 ) gives oxadiazolium salts 211 in good yields. The key step of the synthesis is the ring opening/ring closure process resulting in the sub-…”

“…77 They applied known methodology leading to the triazolium ring formation by the reaction of an amine with an oxadiazolium salt. 76 Detailed procedures for the synthesis of these salts were given in a patent application 78 and presented yields refer to the final step (Scheme 39, bottom).…”