A new domino reaction based on [4+2]‐cycloadditions of pyrido[1,2‐a]pyrazines with azadienophiles

Abstract

The reaction of pyrido[1,2‐a]pyrazines 1 with nitroso compounds 2 provides pyridyl substituted 1,2,4‐triazinones 4 via a domino reaction which involves a cycloaddition and a ring transformation reaction. The intermediate and regioselective formed oxadiazines 4′ were trapped by complexation yielding the (CO)4Mo‐complex 5. Derivatives of diazene such as N‐phenyltriazolindione 6a, phthalazinedione 6b or esters of azodicarboxylic acid 6c‐6f reacted with 1 to give different derivatives of 1,2,4‐triazine 7a‐f. The use of oxygen gave oxadiazinones 8.

Di-t-butyl Azodicarboxylate

“…Only one publication, studying the mechanism of the Mitsunobu reaction, describes a comparative study of several azodicarboxylates, concluding that such reactions can be performed using DBAD. 32 A Mitsunobu-type reaction has been published recently, starting from alcohol (64). Treatment with triphenylphosphine and DBAD gives the hydrazine derivative (65) Reaction with Nucleophiles.…”

Efficient Synthesis of Nitrogen Heterocycles by Cyclization of Bis(nucleophiles) with Oxaldiimidoyl Dichlorides

“…[27] Treatment of 61 with nitrosobenzene (67) afforded the 2,3-dihydro-1,2,4-triazin-6(1H)-one 70 in 86% yield through regioselective formation of the bridged intermediate 68, subsequent ringopening (intermediate 69), and Dimroth rearrangement (Scheme 17). [27a] Treatment of 2 equiv.…”

New heterocycles with cycloamidine substructure and their ringtransformation reactions with acetylene dicarboxylic ester

“…On reacting pyrido [1,2-b] [1,2,4]triazine 7 with dimethyl acetylenedicarboxylate an unexpected ring transformation takes place. Here, at a reaction temperature of 40 °C, in nearly quantitative yields the tricyclic compounds 12a,b were obtained.…”

“…For example, starting from cycloamidines of type 1 by a cycloaddition/ring transformation sequence new compounds such as 2,2-bipyridines [2], azaquinones [3], 1,2,4-triazines [4] and 1,2,5-oxadiazines [4] are accessible. Our work in this area is aimed at the synthesis of further pyridine derivatives, and the 2-hydrazinopyridine 3, 1,2-diaminopyridinium iodide 4 and 1-amino-2-methylpyridinium iodide 5 were chosen as starting materials.…”

“…Elemental analyses were carried out using an automatic analyzer LECO CHNS 932. [2,1-c] [1,2,4]triazin-3-amine (6a, R = Tolyl).…”