Synthesis of Polycarbonyl Pyrroles via K2S2O8-Mediated Oxidative Cyclization of Enamines

Gao, Peng; Wang, Juan; Bai, Zijing; Shen, Li; Yan, Yichao; Yang, Dongxu; Fan, Mingjin; Zhang, Guan

doi:10.1021/acs.orglett.6b03060

Cited by 61 publications

(36 citation statements)

References 66 publications

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“…As reported by Jiang,11 β‐ketosulfone 6 could be prepared by treatment of 3 c with silica gel (95 %), while 2 H ‐azirine 7 was obtained in 65 % yield through hypervalent iodine‐induced oxidative cyclization 20. Unexpectedly, dihydropyrrole 8 was obtained under Bao and Guan's K 2 S 2 O 8 ‐mediated oxidative cyclization conditions, instead of a pyrrole as observed with analogous β‐keto or β‐ester enamines 21. Similarly, a new reaction pattern was discovered on treatment of 3 c with NBS, which afforded polybrominated imine 9 in 72 % yield.…”

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confidence: 77%

Silver‐Catalyzed Stereoselective Aminosulfonylation of Alkynes

et al. 2017

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A silver‐catalyzed intermolecular aminosulfonylation of terminal alkynes with sodium sulfinates and TMSN3 is reported. This three‐component reaction proceeds through sequential hydroazidation of the terminal alkyne and addition of a sulfonyl radical to the resultant vinyl azide. The method enables the stereoselective synthesis of a wide range of β‐sulfonyl enamines without electron‐withdrawing groups on the nitrogen atom. These enamines are found to be suitable for a variety of further transformations.

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confidence: 77%

Silver‐Catalyzed Stereoselective Aminosulfonylation of Alkynes

et al. 2017

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“…[20] Unexpectedly,d ihydropyrrole 8 was obtained under Bao and GuansK 2 S 2 O 8 -mediated oxidative cyclization conditions,instead of apyrrole as observed with analogous b-keto or b-ester enamines. [21] Similarly,anew reaction pattern was discovered on treatment of 3c with NBS,w hich afforded polybrominated imine 9 in 72 %y ield. N-brominated imines have rarely been reported.…”

Section: Angewandte Chemiementioning

confidence: 88%

Silver‐Catalyzed Stereoselective Aminosulfonylation of Alkynes

Ning

Liao

et al. 2017

Angewandte Chemie

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As ilver-catalyzed intermolecular aminosulfonylation of terminal alkynes with sodium sulfinates and TMSN 3 is reported. This three-component reaction proceeds through sequential hydroazidation of the terminal alkyne and addition of as ulfonyl radical to the resultant vinyl azide.T he method enables the stereoselective synthesis of aw ide range of bsulfonyl enamines without electron-withdrawing groups on the nitrogen atom. These enamines are found to be suitable for av ariety of further transformations.Alkynes are one of the most common and versatile functional groups in organic synthesis,and catalytic methods that enable their efficient transformation into other useful functionalities are therefore highly appealing in both academic research and industrial applications.[1] Direct difunctionalization reactions of alkynes,c apable of affording tri-and tetrasubstituted alkenes,h ave attracted much attention in recent years.[2] Among these,r adical-based 1,2-difunctionalizations of alkynes offer astraightforward means to construct functionalized alkenes by reaction with both carbon- [3] and heteroatom-centered radicals [4] with excellent step-and atomeconomy.[5] Mechanistically,ac ommon reaction pathway is observed involving initiation of the reaction by radical addition to the alkyne to generate av inyl radical intermediate,w hich is then coupled with another component to form the alkene product ( Figure 1a). However,s uch vinyl radical species are highly reactive and readily undergo hydrofunctionalization by H-atom abstraction, [6] which is as ignificant challenge in developing radical-based alkyne difunctionalization reactions.M oreover,a liphatic alkynes are generally unreactive in these processes,which is most likely due to the lack of a p-conjugation stabilizing effects of intermediate alkyl-substituted vinyl radicals compared to aryl-substituted analogues.[7] Consequently,c onceptually distinct approaches are in high demand. In the last years,t he nitrogenation of alkynes with trimethylsilylazide (TMSN 3 )has attracted much attention, where carbon-carbon triple bond cleavage leads to av ariety of nitrogen-containing molecules.[8] Building from our recent efforts on the activation of alkynes by silver catalysis, [9] we herein report an ew strategy to effect radicalbased difunctionalization of terminal alkynes through an unprecedented hydroazidation/ radical addition cascade (Figure 1b). Thek ey point for this successful transformation is that we discovered amild and efficient approach to generate sulfonyl radical from sodium sulfinate,t hus avoiding the initial competitive radical addition to alkynes.[6] To the best of our knowledge,t his is the first example of intermolecular alkyne aminosulfonylation, [10] resulting in stereoselective synthesis of b-sulfonyl N-unprotected enamines,w hich are useful synthetic intermediates whose applications are currently limited by al ack of practical synthetic methods for their preparation.[11] Moreover,only one report regarding the synthesis of N-unprotected enami...

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“…(Scheme a). [6a] Although the synthesis of multisubstituted symmetrical pyrroles under transition‐metal‐free conditions have been developed, the synthesis of multisubstituted unsymmetric pyrroles could not be achieved by this method. Thereafter, the construction of pyrrolin‐4‐ones is enabled by a TBHP ( tert ‐butyl hydroperoxide) and TBAI ( tert ‐butyl ammonium iodide) system (Scheme b).…”

Section: Introductionmentioning

confidence: 99%

“…Thereafter, the construction of pyrrolin‐4‐ones is enabled by a TBHP ( tert ‐butyl hydroperoxide) and TBAI ( tert ‐butyl ammonium iodide) system (Scheme b). [6c] Despite these advances, the synthesis of multisubstituted pyrroles on the opposite side of the ester group and the synthesis of pyrrolin‐4‐ones via copper‐catalyzed 1,2‐aryl migration have not been exploited. In our previous work, we have developed the synthetic route for functionalized quinolines from enamino esters and ortho‐halogenated aromatic carbonyl compounds via the copper‐catalyzed tandem reaction (Scheme c).…”

Section: Introductionmentioning

confidence: 99%

Divergent Synthesis of Multisubstituted Unsymmetric Pyrroles and Pyrrolin‐4‐ones from Enamino Esters via Copper‐Catalyzed Aerobic Dimerization

2019

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A facile synthetic method to access multisubstituted unsymmetric pyrrole and pyrrolin‐4‐one derivatives is disclosed. In the presence of Cu(OAc)2 and KOAc, substituted pyrrole derivatives are produced in good yields (up to 93 %) through oxidative cyclization of enamino esters. Meanwhile, using CuCl2 and TFA (trifluoroacetic acid), pyrrolin‐4‐one derivatives are obtained in excellent yields (up to 94 %) through 1,2‐aryl migration. A wide range of functional groups have been tolerated, and a reliable method for the synthesis of valuable multisubstituted pyrroles and pyrrolin‐4‐ones has been developed.

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Synthesis of Polycarbonyl Pyrroles via K₂S₂O₈-Mediated Oxidative Cyclization of Enamines

Cited by 61 publications

References 66 publications

Silver‐Catalyzed Stereoselective Aminosulfonylation of Alkynes

Silver‐Catalyzed Stereoselective Aminosulfonylation of Alkynes

Silver‐Catalyzed Stereoselective Aminosulfonylation of Alkynes

Divergent Synthesis of Multisubstituted Unsymmetric Pyrroles and Pyrrolin‐4‐ones from Enamino Esters via Copper‐Catalyzed Aerobic Dimerization

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