Chemo- and Diastereoselective <i>N</i>-Heterocyclic Carbene-Catalyzed Cross-Benzoin Reactions Using <i>N</i>-Boc-α-amino Aldehydes

Haghshenas, Pouyan; Gravel, Michel

doi:10.1021/acs.orglett.6b02123

Cited by 37 publications

(19 citation statements)

References 71 publications

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“…Such a procedure of reaction between aldehydes and paraformaldehyde was reported by Glorius in 2011 [67]. It is worth noting that the chemoselective cross-benzoin reaction with the use of α-aminoaldehydes as electrophilic agents is also possible [68,69].…”

Section: Scheme 2 Breslow Intermediatementioning

confidence: 85%

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: Scheme 2 Breslow Intermediatementioning

confidence: 85%

Organocatalytic Name Reactions Enabled by NHCs

et al. 2020

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“…For comparison, we used 2-(perfluorophenyl)-6,7-dihydro-5H-pyrrolo[2,1-c][1,2,4]triazol-2-ium tetrafluoroborate, an active NHC for several reactions [45][46][47][48][49][50][51][52], but its performance is similar to the leading catalyst in this report, Table 2, entries 5 vs. 6. However, the fact that the leading catalyst is slightly superior in performance and easier to prepare, by alkylation of benzoimidazole, encouraged us to continue this study using it.…”

Section: Resultsmentioning

confidence: 99%

Benzoin condensation of aromatic aldehydes catalyzed by N-heterocyclic carbenes under mild conditions

et al. 2019

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The benzoin condensation was used to evaluate the catalytic activity of different N-heterocyclic carbenes as a function of their structure and N-substituents. There is a correlation between the length of an N-alkyl substituent and its performance as an organocatalyst. Heteroaromatic aldehydes were found to be the most reactive, among the screened substrates, finishing the reaction in 30 minutes, with almost quantitative yields. On the other hand, p-nitrobenzaldehyde, a strongly electrophilic aldehyde, was the least reactive. Electronic effects have little influence on the reaction yield but steric effects can dramatically reduce it. The preformed organocatalyst reacts faster than the generated in situ, with minimum solvent.

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“…[19] In their total synthesis of this natural product, Haghshenas and Gravel relied on a Breslow intermediate for intermolecular benzoin cyclization (Scheme 6). [20] Reaction of 12 and 13 in the presence of triazolium salt 14 and DIPEA furnished compound 15, and subsequent ketone reduction afforded an amino diol (16) with three contiguous stereocenters (35 %, >20:1 dr). Deprotection of compound 16 yielded natural product 17.…”

Section: Breslow Intermediates In Natural Product Synthesismentioning

confidence: 99%

“…Deprotection of compound 16 yielded natural product 17. The Glorius group reported the total synthesis of taxilamine (20), isolated from the Chinese herb Berberis aristata. [21,22] The crucial step in their synthesis was NHC-catalyzed intramolecular aroylation (Scheme 7).…”

Section: Breslow Intermediates In Natural Product Synthesismentioning

confidence: 99%