Reaction of 2-hydrazino-3-methylquinoxaline with aryl-1,3-diketones: A structural reinvestigation

Abstract

Treatment of 2-hydrazino-3-methylquinoxaline (1) with phenyl-1,3-butanedione (2b) in THF affords regioisomeric 1-(3'-methylquinoxalin-2'-yl)-3(5)-methyl-5(3)-phenylpyrazoles (3b and 4b) as major products along with the formation of small amount of 1,4-dimethyl-1,2,4-triazolo[4,3-a]quinoxaline (5) rather than the reported exclusive formation of 5. Several other regioisomeric 1-(3'-methylquinoxalin-2'-yl)-3,5-disubstituted pyrazoles have similarly been synthesized using other aryl-and heteroaryl-1,3-diketones. The identity of the regioisomeric pyrazoles is based upon NMR ( 1 H & 13 C) spectral data and an unambiguous synthesis.

Facile one pot synthesis of N-fused 1,2,4-triazoles via oxidative cyclisation using DDQ

“…The described oxidative cyclization has previously been reported for the preparation of triazoloquinoxalines. [19][20][21][22][23][24][25] Other methods reported in the literature for the cyclization of the triazole ring usually require a combination of NBS and base, 26 refluxing orthoesters, 27,28 acids, 28,29 desulfurization of thiosemicarbazides, 30 or cyclization of hydrazides in polyphosphoric acid (PPA). 28 A couple of examples of oxidative cyclizations using chloramine-T, 31 phenyliodine bis(trifluoroacetate) or iodobenzene diacetate, 32 ceric ammonium nitrate, 33 catalyzed by KI/TBHP, 34 have also been reported.…”

Synthesis of Some Derivative Quinoxaline

“…Antimalarial and sulfanylamide preparations prepared on the basis of quinoxaline due to their insufficient solubility or toxicity can't satisfy the requirements raised to chemotherapeutic preparations [3][4]. But it should be noted that modification of similar compounds through insertion of functional groups of different nature into their structure, creates definite basis for avoidance of these shortcomings and from the viewpoint of improvement of preparation properties [5][6].…”

Synthesis and Selective Functionalization of [1,2,4]Triazolo-[4,3-a]pyrazines

“…The described oxidative cyclization has previously been reported for the preparation of triazoloquinoxalines. [31][32][33][34][35][36][37] Other methods reported in the literature for the cyclization of the triazole ring usually require a combination of NBS and base, 38 refluxing orthoesters, 39,40 acids, 40,41 desulfurization of thiosemicarbazides, 42 or cyclization of hydrazides in polyphosphoric acid (PPA). 40 A couple of examples of oxidative cyclizations using chloramine-T have previously been reported.…”