scholarly journals Chiral Primary Amine/Ketone Cooperative Catalysis for Asymmetric α-Hydroxylation with Hydrogen Peroxide

Author(s):  
Mao Cai ◽  
Kaini Xu ◽  
Yuze Li ◽  
zongxiu nie ◽  
Long Zhang ◽  
...  

<p>Carbonyl and amine are yin and yang in organocatalysis that mutually activate and transform each other. As intrinsically reacting partners, carbonyl and amine tend to condensate, depleting their individual activity when employed as catalysts. Though widely established as prominent catalytic strategies, aminocatalysis and carbonyl catalysis seems not coexist well and a cooperative amine/carbonyl dual catalysis remains virtually unknown. Here we report a cooperative primary amine and ketone dual catalysis in the asymmetric <i>α</i>-hydroxylation with H<sub>2</sub>O<sub>2</sub>. Besides participating in the typical enamine catalytic cycle, the chiral primary amine catalyst was found to work cooperatively with a ketone catalyst to activate H<sub>2</sub>O<sub>2</sub> <i>via</i> an oxaziridine intermediate derived from<i> in-situ</i> generated ketimine intermediate. The resulted enamine-oxaziridine coupling then facilitated highly-controlled hydroxylation of <i>β</i>-ketocarbonyls that are not possible with other catalytic methods. The dual catalytic approach allows for highly enantioselective <i>α</i>-hydroxylation of a broad range of <i>β</i>-ketocarbonyls. Particularly, late-stage hydroxylation for peptidyl amide or chiral esters can also be achieved with high stereoselectivity. With its operational simplicity and mild conditions, this cooperative amine/ketone catalysis provides a new strategy in catalytic activation of H<sub>2</sub>O<sub>2</sub> and expands the domain of typical amine and carbonyl catalysis to include those challenging transformations.</p>

2020 ◽  
Author(s):  
Mao Cai ◽  
Kaini Xu ◽  
Yuze Li ◽  
zongxiu nie ◽  
Long Zhang ◽  
...  

<p>Carbonyl and amine are yin and yang in organocatalysis that mutually activate and transform each other. As intrinsically reacting partners, carbonyl and amine tend to condensate, depleting their individual activity when employed as catalysts. Though widely established as prominent catalytic strategies, aminocatalysis and carbonyl catalysis seems not coexist well and a cooperative amine/carbonyl dual catalysis remains virtually unknown. Here we report a cooperative primary amine and ketone dual catalysis in the asymmetric <i>α</i>-hydroxylation with H<sub>2</sub>O<sub>2</sub>. Besides participating in the typical enamine catalytic cycle, the chiral primary amine catalyst was found to work cooperatively with a ketone catalyst to activate H<sub>2</sub>O<sub>2</sub> <i>via</i> an oxaziridine intermediate derived from<i> in-situ</i> generated ketimine intermediate. The resulted enamine-oxaziridine coupling then facilitated highly-controlled hydroxylation of <i>β</i>-ketocarbonyls that are not possible with other catalytic methods. The dual catalytic approach allows for highly enantioselective <i>α</i>-hydroxylation of a broad range of <i>β</i>-ketocarbonyls. Particularly, late-stage hydroxylation for peptidyl amide or chiral esters can also be achieved with high stereoselectivity. With its operational simplicity and mild conditions, this cooperative amine/ketone catalysis provides a new strategy in catalytic activation of H<sub>2</sub>O<sub>2</sub> and expands the domain of typical amine and carbonyl catalysis to include those challenging transformations.</p>


2021 ◽  
Author(s):  
Rafał Kusy ◽  
Karol Grela

Herein, we present (<i>Z</i>)-selective transfer semihydrogenation of alkynes based on in situ generated CuNPs in the presence of hydrogen donors, such as ammonia-borane and a protic solvent. This environmentally-friendly method is characterized by operational simplicity combined with high stereo- and chemoselectivity and functional group compatibility. Auto-oxidation of CuNPs after the semihydrogenation reaction is completed results in the formation of water-soluble ammonia complex, so that the catalyst may be reused several times by simple phase-separation with no need of any special regeneration process. Formed NH<sub>4</sub>B(OR)<sub>4</sub> can be easily transformed back to ammonia-borane or to boric acid. In addition, one-pot tandem sequence involving Suzuki reaction followed by semihydrogenation was presented.<br>


2019 ◽  
Vol 15 ◽  
pp. 1061-1064 ◽  
Author(s):  
Alexei Lukin ◽  
Anna Bakholdina ◽  
Anna Kryukova ◽  
Alexander Sapegin ◽  
Mikhail Krasavin

A three-component reaction involving in situ generation of propargylureas and subsequent Zn(OTf)2-mediated cyclocondensation with a primary amine yielded trisubstituted 2-aminoimidazoles. These findings are in contrast to the previously reported base-promoted unimolecular cyclization of propargylureas (leading to 2-imidazolones) and extend the range of Lewis acid-catalyzed azole syntheses based on N-carbonyl propargylamines.


Author(s):  
Zahra Abdi ◽  
Robabeh Bagheri ◽  
Mohammad Reza Mohammadi ◽  
Zhenlun Song ◽  
Mikaela Görlin ◽  
...  

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Valeria Nardone ◽  
Sergio Fabbri ◽  
Francesca Marini ◽  
Roberto Zonefrati ◽  
Gianna Galli ◽  
...  

In recent years, there has been an increasing interest in interactive application principles of biology and engineering for the development of valid biological systems for tissue regeneration, such as for the treatment of bone fractures or skeletal defects. The application of stem cells together with biomaterials releasing bioactive factors promotes the formation of bone tissue by inducing proliferation and/or cell differentiation. In this study, we used a clonal cell line from human adipose tissue-derived mesenchymal stem cells (hADSCs or preadipocytes), named PA2-E12, to evaluate the effects of strontium (Sr2+) released in the culture medium from an amidated carboxymethylcellulose (CMCA) hydrogel enriched with different Sr2+concentrations on osteodifferentiation. The osteoinductive effect was evaluated through both the expression of alkaline phophatase (ALP) activity and the hydroxyapatite (HA) production during 42 days of induction. Present data have shown that Sr2+released from CMCA promotes the osteodifferentiation induced by an osteogenic medium as shown by the increase of ALP activity at 7 and 14 days and of HA production at 14 days. In conclusion, the use of biomaterials able to releasein situosteoinductive agents, like Sr2+, could represent a new strategy for future applications in bone tissue engineering.


2016 ◽  
Vol 23 (6) ◽  
pp. 1253-1257 ◽  
Author(s):  
Yunbo Zhu ◽  
Wen-Zhao Zhang ◽  
Long Zhang ◽  
Sanzhong Luo

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