Facile Synthesis of Onychines

Arita, Mao; Yokoyama, Saichiro; Asahara, Haruyasu; Nishiwaki, Nagatoshi

doi:10.1055/s-0037-1612058

Cited by 7 publications

(2 citation statements)

References 10 publications

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“…Consequently, the development of new synthetic methods to access appropriate 2‐arylnicotinate esters has been the topic of extensive research. Published methods include Suzuki‐Miyaura coupling, [22a] condensation of 1,5‐dicarbonyl compounds with hydroxylamine hydrochloride, [22b,c,24] C−H arylation of 2‐halopyridine N ‐oxides with Grignard reagents, [22d] multicomponent tandem reaction using a Blaise intermediate, [26] FeCl 3 ‐mediated condensation of α‐phenylenamino esters and enones [22f] and reaction of azatrienes with α,β‐unsaturated aldehydes as their key steps [27] . Although no example for onychine ( 4 ) synthesis was provided, tert ‐butyl hydroperoxide (TBHP) has been successfully employed in the radical cyclization of 3‐hydroxymethyl‐2‐phenylpyridine, 2‐(pyridinyl)benzylalcohols [28] and nicotinaldehydes [29] for the synthesis of various 1‐, 2‐, 3‐ and 4‐azafluorenones, respectively.…”

Section: Introductionmentioning

confidence: 99%

Collective Total Synthesis of 4‐Azafluorenone Alkaloids

Jourjine

Bracher

2023

Eur J Org Chem

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4-Azafluorenones are typically obtained by acid-mediated cyclization of 2-arylnicotinates. However, this approach fails to give 5-oxygenated 4-azafluorenones due to lactonization of 2-(2-alkoxy)phenylnicotinate intermediates. Herein, we report two modifications of established approaches to 4-azafluorenone synthesis that, either in combination or by themselves, enable the flexible preparation of 4-azafluorenones with diverse oxygenation patterns in the benzenoid ring. Undesired lactonization was circumvented via tert-butyl hydroperoxide (TBHP)mediated radical cyclization of 2-aryl-3-(hydroxymeth-yl)pyridines. In the absence of suitable protecting groups for phenolic intermediates, bromide substituents were regioselectively introduced as latent hydroxy groups and later converted under palladium catalysis. We present the first total syntheses of five 4-azafluorenone alkaloids muniranine, darienine, 5,8dimethoxy-7-hydroxyonychine, 5,6,7,8-tetramethoxyonychine, and 6,8-dihydroxy-7-methoxyonychine in addition to new total syntheses of six 4-azafluorenone alkaloids and one related pyridocoumarin alkaloid.

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Section: Introductionmentioning

confidence: 99%

Collective Total Synthesis of 4‐Azafluorenone Alkaloids

Jourjine

Bracher

2023

Eur J Org Chem

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“…Our investigations were initiated with the reaction of conjugated enynones 1a and 4 equiv of ( Z )-ethyl 3-amino-3-phenyl acrylate 2a in dichloromethane (DCM) at 25 °C under nitrogen atmosphere. The mixture was stirred vigorously for 0.5 to 1.5 h until TLC indicated complete consumption of the starting material 1a .…”

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confidence: 99%

Silver(I)-Catalyzed Domino Cyclization/Cyclopropanation/Ring-Cleavage/Nucleophilic Substitution Reaction of Enynones with Enamines: Synthesis of 4-(Furan-2-yl)-3,4-dihydro-2H-pyrrol-2-one

2020

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We report the synthesis of 4-(furan-2-yl)-3,4-dihydro-2H-pyrrol-2-one derivatives. In this approach, two core structures, the furan ring and 3,4-dihydro-2H-pyrrol-2-one, are constructed via silver(I)-catalyzed cascade cyclization/cyclopropanation/ring-cleavage/nucleophilic substitution reaction of enynones with enamines. A reasonable mechanism has been proposed. This method possesses some advantages such as high chemoselectivity, mild reaction conditions, simple operation, and short reaction time.

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Domino synthesis of functionalized pyridine carboxylates under gallium catalysis: Unravelling the reaction pathway and the role of the nitrogen source counter anion

Kumar

Sharma

Saha

et al. 2022

Chemistry An Asian Journal

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The catalytic potential of various metal Lewis acid catalysts have been assessed to derive a high-yielding, multicomponent domino synthesis of functionalized pyridines from (E)-3-(dimethylamino)-1-aryl/heteroaryl-prop-2-en-1ones, 1,3-dicarbonyl compounds, and an ammonium salt (as the nitrogen precursor). Amongst the various metal halides, tetrafluoroborates, perchlorates, and triflates used as the catalyst, GaI 3 proved to be the most effective. The mechanistic course of the most plausible pathway has been outlined as the intermediate formation of imine/enamine by the reaction of the 1,3-dicarbonyl compound with ammonia (liberated in situ from the ammonium salt used as the nitrogen source), which participates in the domino nucleophilic Michael reaction to the (2E)-3-(dimethylamino)-1-aryl/ hetroarylprop-2-en-1-one by its active methylene carbon through its enamine form followed by intramolecular cyclization and aromatization. The effect of different ammonium salts as the nitrogen source has been investigated and NH 4 OAc was found to be best. The influence of the acetate counter anion of NH 4 OAc on the progress of the reaction was studied and its specific role in the cyclization and subsequent aromatization has been revealed. This work offers distinct advantages compared to the literature reported methodologies on the count of several green index parameters.

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Facile Synthesis of Onychines

Cited by 7 publications

References 10 publications

Collective Total Synthesis of 4‐Azafluorenone Alkaloids

Collective Total Synthesis of 4‐Azafluorenone Alkaloids

Silver(I)-Catalyzed Domino Cyclization/Cyclopropanation/Ring-Cleavage/Nucleophilic Substitution Reaction of Enynones with Enamines: Synthesis of 4-(Furan-2-yl)-3,4-dihydro-2H-pyrrol-2-one

Domino synthesis of functionalized pyridine carboxylates under gallium catalysis: Unravelling the reaction pathway and the role of the nitrogen source counter anion

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