Mn-mediated sequential three-component domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction towards annulated imidazo[1,2-a]pyridines

• Olga A. Storozhenko,
• Alexey A. Festa,
• Delphine R. Bella Ndoutoume,
• Alexander V. Aksenov,
• Alexey V. Varlamov and
• Leonid G. Voskressensky

Beilstein J. Org. Chem. 2018, 14, 3078–3087, doi:10.3762/bjoc.14.287

• proceeds through a domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction sequence. Keywords: 2-aminochromene; domino reaction; imidazo[1,2-a]pyridine; 2-iminochromene; Michael addition; multicomponent reaction; oxidation; pyridine amination; Introduction Domino reactions are well

• promising anticancer activity [34], thereby showing the importance of this merged heterocyclic skeleton (Figure 1). The formation of the chromene and imidazole rings in a single-step procedure was independently discovered by us [35][36] and Proença et al. [37][38], who identified 2-iminochromene 3 to be the

• , complicated by the need of an oxidant to fulfil the final aromatization. Following our interest in domino [42][43] and MCR chemistry [44][45] and taking an advantage of 2-iminochromene reactivity, herein we report a sequential three-component domino reaction of salicylaldehydes 2 and N-(cyanomethyl)pyridinium

Reactions of salicylaldehyde and enolates or their equivalents: versatile synthetic routes to chromane derivatives

• Ishmael B. Masesane and
• Zelalem Yibralign Desta

Beilstein J. Org. Chem. 2012, 8, 2166–2175, doi:10.3762/bjoc.8.244

• used. Chromane derivatives from the reactions of salicylaldehyde and enolate equivalents derived from malononitrile and its derivatives The one-pot reaction of salicylaldehyde and malononitrile has proved to be an efficient method for the synthesis of 2-iminochromene derivatives. In general such

• synthetic procedures involve a Knoevenagel condensation followed by intramolecular cyclization. In a detailed study directed towards understanding the pathway of the reaction of salicylaldehyde (5) and malononitrile (20), Costa and co-workers reported the efficient synthesis of 2-iminochromene 21 in 90

• -diethylamino- and 5-bromo-3-methoxy-substituted salicylaldehydes gave corresponding 2-iminochromene derivatives in 86–100% yields, while the lowest yield of 62% was achieved when 3,4-dihydroxysalicylaldehyde was used. Further studies by Costa and co-workers revealed that the reaction of salicyldehyde (5) with