Intramolecular cyclization of N-propargylic β-enaminones catalyzed by silver

Martins, Marcos A. P.; Rossatto, Marcelo; Frizzo, Clarissa P.; Scapin, Elisandra; Buriol, Lilian; Zanatta, Nilo; Bonacorso, Hélio G.

doi:10.1016/j.tetlet.2012.11.086

Cited by 43 publications

(26 citation statements)

References 35 publications

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“…Among the Lewis acids examined, silver salts were efficient and AgOTf afforded the best result, whereas CuOTf was not effective. 108 This reaction was successfully catalysed by AgNO 3 (10 mol%). 106 In 2013, Wang and co-workers extended the protocol to monocarbonyl compounds, a-ketopropargylamines 113, which underwent 5-endo-dig carbocyclization, affording 3-pyrrolines 114 in 49-91% yields with good functional group tolerance (Scheme 47).…”

Section: Cycloisomerizationmentioning

confidence: 99%

Silver-catalysed reactions of alkynes: recent advances

2015

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Silver is a less expensive noble metal. Superior alkynophilicity due to π-coordination with the carbon-carbon triple bond makes silver salts ideal catalysts for alkyne-based organic reactions. This review highlights the progress in alkyne chemistry via silver catalysis primarily over the past five years (ca. 2010-2014). The discussion is developed in terms of the bond type formed with the acetylenic carbon (i.e., C-C, C-N, C-O, C-Halo, C-P and C-B). Compared with other coinage metals such as Au and Cu, silver catalysis is frequently observed to be unique. This critical review clearly indicates that silver catalysis provides a significant impetus to the rapid evolution of alkyne-based organic reactions, such as alkynylation, hydrofunctionalization, cycloaddition, cycloisomerization, and cascade reactions.

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Section: Cycloisomerizationmentioning

confidence: 99%

Silver-catalysed reactions of alkynes: recent advances

2015

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“…If the N atom of N ‐propargyl enaminones is trisubstituted, 1,6‐dihydropyridines can be also formed in the presence of a Cu(I)‐catalyst (3–10 mol%) . Similar results were obtained in the presence of AgNO 3 (10 mol%) . Using CuCl 2 (20 mol%) and a base, N ‐propargyl enaminones cyclize into pyrroles .…”

Section: Methodsmentioning

confidence: 57%

“…[23] Similar results were obtained in the presence of AgNO 3 (10 mol%). [24] Using CuCl 2 (20 mol%) and a base, N-propargyl enaminones cyclize into pyrroles. [25] Finally, with stoichiometric amounts of ZnCl 2 , the cyclization leads to the 7-membered ring 1,4-oxazepines.…”

mentioning

confidence: 99%

Synthesis of 3‐Keto Pyridines from the Conjugated Allenone – Alkynylamine Oxidative Cyclization Catalyzed by Supported Au Nanoparticles

et al. 2020

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Recyclable supported Au nanoparticles on TiO2 catalyze the cyclization of N‐propargyl or N‐homopropargyl β‐enaminones followed by dehydrogenation (aromatization) leading to substituted 3‐keto pyridines or 4‐picolines in very good yields. This pathway is in contrast to their known cyclization in the presence of Au(I) or Au(III) catalysts which provides 1,4‐oxazepines, instead. The enaminones are formed in situ upon mixing a conjugated allenone or allenyl ester with the alkynylamine, thus the pyridine‐forming transformation is typically a one pot process.

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“…Taking into account for the experimental results on the conversions of deuterium labeled 14a (see Supplementary Schemes S1-S2), 28 could presumably be formed through a hydride shift generating a zwitterionic intermediate composed of a pyridinium cation and an enolate anion, which would undergo subsequent 7-endo cyclization. 28 In contrast to the identical conversion of 13a into 14a under gentle heating at 60 °C, yielding the iboga-skeleton (23) as the major product (Fig. 3), 23 was not obtained at all at 120 °C.…”

Section: Redox-mediated Cyclization Reactions Leading To 28 and 29mentioning

confidence: 86%

“…Whereas approaches to the synthesis of substituted pyridines via oxidation of temporarily formed DHPs have been relatively well explored, [19][20][21] protocols for obtaining DHP rings via metal-catalyzed 6-endo cyclization of N-propargyl enaminocarbonyls are limited. 22,23 In our system, rapid construction of the 1,6-DHP ring was required under very mild conditions without causing further intra-and intermolecular reactions of the elaborate π-conjugated systems in 14. As shown in Fig.…”

Section: Development Of Cu(i)-catalyzed Cyclization To Form the Dhp Rmentioning

confidence: 99%