N‐Heterocyclic Carbene Catalyzed [4+2] Cycloaddition of Nitroalkenes with Oxodienes

Chen, Xiangyu; Sun, Lingyi; Ye, Song

doi:10.1002/chem.201204539

Cited by 53 publications

(16 citation statements)

References 143 publications

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“…259 The reaction is believed to proceed via a Rauhut-Currier type mechanism, where the nitroalkene-carbene adduct adds 1,4 to the enone, followed by displacement of the alkyl azolium by the enolate oxygen. Interestingly, the desired [4+2] cycloadduct is formed in only trace amounts when DABCO or PPh 3 are used instead of thiazolium G 30 .…”

Section: Lewis Base Catalysismentioning

confidence: 99%

Organocatalytic Reactions Enabled by N-Heterocyclic Carbenes

et al. 2015

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Section: Lewis Base Catalysismentioning

confidence: 99%

Organocatalytic Reactions Enabled by N-Heterocyclic Carbenes

et al. 2015

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“…Although the nucleophilicity values are not known for the nitronate intermediates, rate ratios can be estimated by using Equation (4). Here again, prediction of this ratio is quite straightforward by using Mayr's approach.…”

Section: Resultsmentioning

confidence: 99%

Morita–Baylis–Hillman Reactions with Nitroalkenes: A Case Study

2015

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We report on the use of a highly reactive super‐DMAP catalyst in Morita–Baylis–Hillman (MBH) reactions of nitroalkenes with ethyl glyoxylate, which result in excellent conversions and short reaction times with, importantly, very low catalyst loading. An extensive study of this particular reaction is presented, which examines all mechanistic and experimental details. Several critical points were hence uncovered that include the correlation between reaction efficiency and Lewis basicity of the catalyst; the double role played by the promoter, primarily as a nucleophilic activator towards the nitroalkene, and as a Brønsted base that triggers glyoxylate depolymerisation. More generally, the limitations in the choice of electrophiles that can engage efficiently in MBH‐type transformations are rationalized by the competition between a productive pathway and a nitroalkene polymerization process. Other aspects of this transformation, used as a case study, are presented in the light of physical organic chemistry.

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“…Furthermore, they declared that the NHC catalysis behaved good applicability to b-substituted nitroalkenes, which was not feasible in the presence of DABCO or phosphine (Scheme 20). 49 Subsequently, Li et al provided a method to prepare functionalized thiazolopyrones. They received the target [4 + 2] cycloadducts via the reaction between aliphatic aldehydes and thiazolones 73 in the presence of NHC C21 generated from the triazolium C4 and NaOAc, the desired products 74 were obtained in moderate to good yields 50 (Scheme 21a).…”

Section: Scheme 19mentioning

confidence: 99%