Diaza-1,3-butadienes as Useful Intermediate in Heterocycles Synthesis

Abstract

Many heterocyclic compounds can be synthetized using diaza-1,3-butadienes (DADs) as key structural precursors. Isolated and in situ diaza-1,3-butadienes, produced from their respective precursors (typically imines and hydrazones) under a variety of conditions, can both react with a wide range of substrates in many kinds of reactions. Most of these reactions discussed here include nucleophilic additions, Michael-type reactions, cycloadditions, Diels–Alder, inverse electron demand Diels–Alder, and aza-Diels–Alder reactions. This review focuses on the reports during the last 10 years employing 1,2-diaza-, 1,3-diaza-, 2,3-diaza-, and 1,4-diaza-1,3-butadienes as intermediates to synthesize heterocycles such as indole, pyrazole, 1,2,3-triazole, imidazoline, pyrimidinone, pyrazoline, -lactam, and imidazolidine, among others. Fused heterocycles, such as quinazoline, isoquinoline, and dihydroquinoxaline derivatives, are also included in the review.

Aza-Povarov Reaction. A Method for the Synthesis of Fused Tetracyclic Chromeno[4,3-d]pyrido[1,2-a]pyrimidines

“…A different activation, with Brønsted acids instead of Lewis acids, in the intramolecular Povarov reaction would be a great challenge, as it would change the reaction requirements and modulate in a very interesting way the orientation of the fused heterocycles formed. In other words, in this case, we would be dealing with an intramolecular Povarov reaction involving a 1,3-diazadienic system (Scheme b) and a dienophile. Previous works reported the synthesis of polycyclic compounds by intermolecular reaction of 1,3-diazadiene with enolethers and cyclopentadiene and an intramolecular one using aminothiazole as the aromatic amine precursor .…”

Editorial: Heterodienes in organic synthesis

“…Third, being highly polarized 1,4-synthons, heterodienes are convenient partners for stepwise [4 + 1]- [4 + 3]- and [4 + 4]- and other [4 + n]-annulation processes involving ylides, carbenoids, and related species ( Selvaraj et al, 2020 ; Ushakov et al, 2022 ; Wang et al, 2024 ). Additionally, they are commonly involved in multi-component condensation reactions that lead to the formation of valuable heterocyclic scaffolds ( Attanasi et al, 2009 ; Lopes et al, 2018 ; Heredia-Moya et al, 2022 ). Heterodiene reactions can be conducted using a variety of organo- and metal-based catalysts, enabling the asymmetric synthesis of valuable products, especially those found in natural sources and pharmaceuticals.…”

Modular synthesis of conjugated enamidines and cascade annulation toward benzofuran-3-oxoacetate

“…Azadienes 2 ( e.g. , 1-aza-1,3-butadienes, 3 2-aza-1,3-butadienes 4 and 1,3-diazabuta-1,3-dienes 5 ) have been proven versatile building blocks in organic synthesis (Scheme 1). Imine 2-aza-1,3-dienes are polyvalent key intermediates for the synthesis of nitrogen compounds and have been widely employed in cycloadditions to access novel and complex heterocyclic derivatives.…”