Enantioselective N‐Heterocyclic Carbene Catalysis via the Dienyl Acyl Azolium

Gillard, Rachel M.; Fernando, Jared E. M.; Lupton, David W.

doi:10.1002/anie.201712604

Cited by 52 publications

(20 citation statements)

References 80 publications

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“…As mentioned, one of the mechanistic fundamentals of the Claisen-type reactions is the generation of α,β-unsaturated acylazolium ( Scheme 7 ). Formation of this intermediate is usually carried out via the reaction of NHCs with α,β-unsaturated enol esters or ethers [ 84 , 85 , 86 ], ynals [ 87 , 88 , 89 , 90 ], 2-bromoenals [ 91 , 92 , 93 , 94 ], or acyl fluorides [ 95 , 96 ]. Moreover, formation α,β-unsaturated acylazolium is possible via two-electron oxidation of Breslow intermediate [ 97 , 98 , 99 , 100 , 101 , 102 , 103 ].…”

Section: Coates–claisen and Ireland–coates–claisen Rearrangementsmentioning

confidence: 99%

Organocatalytic Name Reactions Enabled by NHCs

et al. 2020

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Giving reactions the names of their discoverers is an extraordinary tradition of organic chemistry. Nowadays, this phenomenon is much rarer, although already named historical reactions are still often developed. This is also true in the case of a broad branch of N‑heterocyclic carbenes catalysis. NHCs allow many unique synthetic paths, including commonly known name reactions. This article aims to gather this extensive knowledge and compare historical reactions with current developed processes. Furthermore, this review is a great opportunity to highlight some of the unique applications of these procedures in the total synthesis of biologically active compounds. Hence, this concise article may also be a source of knowledge for scientists just starting their adventure with N‑heterocyclic carbene chemistry.

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Section: Coates–claisen and Ireland–coates–claisen Rearrangementsmentioning

confidence: 99%

Organocatalytic Name Reactions Enabled by NHCs

et al. 2020

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“…In the context of their studies on the NHC‐catalyzed generation of α,β‐unsaturated acyl azolium intermediates and their interception with in‐situ‐generated enolates, the Lupton group very recently demonstrated an NHC‐catalyzed generation of dienyl azolium intermediates . An NHC‐catalyzed reaction of silyl enol ether 83 with dienyl acyl fluoride 84 in the presence of a chiral NHC that was generated from triazolium salt K resulted in the enantioselective synthesis of cyclohexene‐fused β‐lactones 85 that contained three contiguous stereocenters in high yields with excellent ee values (Scheme ).…”

Section: Nhc Catalysismentioning

confidence: 99%

Recent Advances in the Organocatalytic Enantioselective Synthesis of Functionalized β‐Lactones

Mukherjee

Biju

2018

Chemistry An Asian Journal

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This Focus Review highlights recent developments in the organocatalytic enantioselective synthesis of β-lactone derivatives. Owing to the importance of β-lactones as a heterocyclic motif that is present in a variety of natural products and biologically active molecules, several catalytic methods have been developed for the synthesis of these compounds in their enantiomerically pure form. Organocatalytic methods that employ N-heterocyclic carbenes (NHCs), cinchona alkaloids, isothioureas, 4-dimethylaminopyridine (DMAP) derivatives, and phosphines have allowed the highly enantioselective synthesis of β-lactones from cheap and readily available starting materials. Moreover, the inherent strain in the four-membered ring of β-lactones has also been utilized in further synthetic transformations, thus making β-lactones a versatile intermediate in organic synthesis.

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“… 3 In the recent years, processes in which NHC-catalyzed reactions take place via normal-polarity intermediates have gained importance. There are four well-studied paths of generating α,β-unsaturated acyl azoliums: the reactions of NHCs with α,β-unsaturated enol esters or acyl fluorides, 4 ynals, 5 2-bromoenals, 6 or stoichiometric oxidation of Breslow intermediates. 7 …”

Section: Introductionmentioning

confidence: 99%

Construction of Dihydropyrido[2,3-d]pyrimidine Scaffolds via Aza-Claisen Rearrangement Catalyzed by N-Heterocyclic Carbenes

2020

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N -Heterocyclic carbenes (NHCs) catalyzing aza-Claisen rearrangement of α,β-unsaturated enals with cyclic vinylogous amides under oxidative conditions generating potentially biologically active dihydropyridinone-fused uracils have been developed. This strategy represents a unique NHC-activation-based path with the use of 6-aminouracils as stable α,β-diEWG cyclic vinylogous amides for the efficient synthesis of bicyclic N -unprotected lactams similar to those in many useful drugs.

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Enantioselective N‐Heterocyclic Carbene Catalysis via the Dienyl Acyl Azolium

Cited by 52 publications

References 80 publications

Organocatalytic Name Reactions Enabled by NHCs

Organocatalytic Name Reactions Enabled by NHCs

Recent Advances in the Organocatalytic Enantioselective Synthesis of Functionalized β‐Lactones

Construction of Dihydropyrido[2,3-d]pyrimidine Scaffolds via Aza-Claisen Rearrangement Catalyzed by N-Heterocyclic Carbenes

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