Modification and application of 1,2,5-oxadiazolo[3,4-b]pyrazine derivatives: highlights and perspectives

From Conventional to Sustainable Catalytic Approaches for Heterocycles Synthesis

“…Structure modification and fabrication of new heterocycles can be performed also through nucleophilic aromatic substitution of hydrogen with direct CÀ H bond functionalization without transition metals catalyst. [14] All these synthetic approaches exploit the use of modern techniques, that also aimed to improve the sustainability of the synthetic approach, such as photochemistry, [15] electrochemistry, [16] micro-wave [17] or ultra-sound irradiation, [18] employing of ionic liquids as solvents. [19] Considering the great importance of these compounds, the development of effective catalytic strategies represents a fundamental tool for the synthesis of heterocycles.…”

A co-crystal of heterobicyclic isomers as a product of the cyclocondensation reaction of 3,4-diaminofurazan with diethyl-2-oxosuccinate

“…Various aspects of the chemistry and use of furazanopyrazines are covered in two reviews. 29,30 The introduction of the required substituents to the furazanopyrazine core is sometimes difficult. An attractive way to provide side functionality is by cyclocondensation of 3,4-diaminofurazane (1) with a 1,2-dicarbonyl compound that carries the desired substituents as part of its structure.…”

(E)-2-(6-(4′-(Diphenylamino)-[1,1′-biphenyl]-2-yl)-[1,2,5]oxadiazolo[3,4-b]pyrazin-5(4H)-ylidene)-2-(6-(4′-(diphenylamino)-[1,1′-biphenyl]-2-yl)-[1,2,5]oxadiazolo[3,4-b]pyrazin-5-yl)acetonitrile

“…Oxadiazolo [3,4-b]pyrazines, also known as furazanopyrazines, have gained considerable attention from researchers working in the fields of both medicinal chemistry [1] and material science as promising high-energy compounds [2], molecular magnets [3], and nonlinear optical [4], sensor [5], and semiconductor materials [6,7]. One of the modern methods for modifying the furazanopyrazine core is the direct functionalization of the C-H bond through the metal-free nucleophilic aromatic substitution of hydrogen (the so-called S N H reactions) [8]. Previously, it has been shown that 1,4-diazine derivatives react with CH-active methylene compounds to form either furo [2,3-b]prazines (route I) or to give the corresponding ylidene derivatives (route II) (Scheme 1).…”