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Shchepin, V. V.; Sazhneva, Yu. Kh.; Russkikh, N. Yu.; Вахрин, М. И.

doi:10.1023/a:1026191021119

Cited by 2 publications

(5 citation statements)

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“…According to the Link's studies, the O ‐acylation of 4‐hydroxycoumarins and 4‐hydroxypyrones is a normal tendency in the simple reaction with aromatic acid chlorides in the presence of pyridine . In addition, a similar result was reported by Vakhrin et al . In their study, zinc enolate of 3‐alkyl‐6‐aryl‐5,5‐dimethyl‐2,3,5,6‐tetrahydropyrone‐2,4‐diones reacted with acid chlorides to form O ‐acylation products.…”

Section: Methodssupporting

confidence: 57%

“…Even though zinc enolate delivered from our protocol demonstrated a positive reactivity toward benzyl bromide, slightly lower yields were obtained compared to the corresponding sodium enolate . According to several reports, zinc enolates are poor nucleophiles for subsequent alkylation reactions especially when the reactions are carried out in ethereal solvent .…”

Section: Methodsmentioning

confidence: 91%

“…From this result, we hypothesize that the thus‐formed complexes ( I and II ) played a double role as the zinc enolate and zinc sulfinate, separately, in the reaction with benzyl halide. Albeit the zinc enolate obtained from our protocol revealed a different reactivity from that of Vakhrin's, however, a further mechanistic study would be required to understand the double C ‐alkylation.…”

Section: Methodsmentioning

confidence: 95%

“…To verify the formation of the zinc complexes ( I and II , Scheme ), further experiments were conducted using different electrophiles. Since the earlier work by Vakhrin and coworker also showed that a β‐ketoester type enolate, sodium enolate of pyrone derivatives, reacted with benzyl bromides to give mainly C ‐alkylation products in low to moderate yields (9–68%), and, interestingly, no product was obtained using the corresponding zinc enolate. Therefore, for the comparative study, we selected benzyl halides as the next suitable electrophiles.…”

Section: Methodsmentioning

confidence: 99%

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Zinc Enolate/Sulfinate Prepared from a Single‐Run Reaction Using Zinc Dust with O‐Tosylated 4‐Hydroxy Coumarin and Pyrone

Shin

Joo

Kim

2016

Bulletin Korean Chem Soc

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Impressive applications of coumarin and pyrone scaffolds have been established in a wide range of biological areas such as antioxidants, antifungals, antibiotics, antibacterial agents, and diverse inhibitors. 1 Of these analogs, 4substituted coumarin or pyrone moieties have shown very interesting biological properties. In addition to their increasing significance, more diverse synthetic tools for the preparation of the 4-functionalized derivatives are required. In order to achieve the primary goal, a large number of intensive efforts has been devoted to exploring versatile approaches utilizing transition-metal-catalyzed crosscoupling reactions as they are recognized to be one of the most powerful tools for the construction of new carboncarbon bond. 2 Regarding the synthetic approaches utilizing transitionmetal catalysts, a variety of well-known reactions such as the Suzuki-Miyaura system with tosylate 3 and triflate, 4 Rh(I)-catalyzed arylboronic acid, 5 Heck coupling, 6 Stille coupling, 7 organoindium, 8 and triarylbismuth 9 have been accomplished for the synthesis of coumarin and pyrone analogs. In addition, both tosylate and phosphate substrates were utilized in the couplings with organozinc reagent. 10 Taking account of the easy accessibility of tosylates, we decided to investigate the possibility of the direct preparation of the corresponding organomanganese coumarin and pyrone reagents by the reaction of highly active manganese. However, contrary to our expectations, the oxidative addition of the active manganese occurred into the oxygensulfur bond forming enolate and sulfinate anologs. 11 With these results in our hand, we next applied this strategy to the preparation of zinc complexes utilizing zinc dust. From the practical point of view, utilizing zinc dust has potential merits since there is no need for a metal-activation procedure. Herein, we disclose an alternative approach to expand the scope of zinc complexes for the synthesis of coumarin and pyrone derivatives. We anticipated that a combination of zinc dust, LiCl and a catalytic amount of iodine would be suitable conditions. 12 As in the standard procedure employed for the oxidative addition of a metal into organic substrates, 2-oxo-2H-chromen-4-yl 4-methylbenzenesulfonate (A) was treated with 2.0 equiv of zinc dust, 2.0 equiv of LiCl and iodine (10 mol%) in dimethyl acetamide (DMA). The progress of the reaction was monitored by GC analysis. After refluxing for 12 h, GC analysis showed the complete consumption of compound A. Therefore, we assumed that the oxidative addition of zinc completed to afford a zinc complex. Next, the thus-formed zinc complex (I) was employed to the cross-coupling reaction with acid chlorides in the presence of a catalytic amounts of Ni(PPh 3 ) 2 Cl 2 . 13 The coupling reactions proceeded smoothly in DMA at room temperature, affording the coupling products. The 13 C NMR spectrum of the major product clearly showed two carbonyl carbon peaks in the range 161-163 ppm, corresponding to the carbonyls of ester. No keto carbonyl ...

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Section: Methodssupporting

confidence: 57%

Section: Methodsmentioning

confidence: 91%

Section: Methodsmentioning

confidence: 95%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Zinc Enolate/Sulfinate Prepared from a Single‐Run Reaction Using Zinc Dust with O‐Tosylated 4‐Hydroxy Coumarin and Pyrone

Shin

Joo

Kim

2016

Bulletin Korean Chem Soc

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“…[2] Aryldiazonium salts were recognized as candidates, as their N -electrophilicity has been exploited to diazenate several classes of carbon nucleophiles in a non-stereoselective fashion, including aromatics, [3] enolates, [4] and heteroaromatics. [5] Reports of Gomberg–Bachmann–Hey biaryl syntheses [3b] and azo-coupling reactions [3a,c] that utilize aryldiazoniums under phase-transfer conditions further encouraged our efforts in this area.…”

mentioning

confidence: 99%

Chiral Anion Phase Transfer of Aryldiazonium Cations: An Enantioselective Synthesis of C3‐Diazenated Pyrroloindolines

et al. 2014

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Herein is reported the first asymmetric utilization of aryldiazonium cations as a source of electrophilic nitrogen. This is achieved through a chiral anion phase-transfer pyrroloindolinization reaction that forms C3-diazenated pyrroloindolines from simple tryptamines and aryldiazonium tetrafluoroborates. The title compounds are obtained in up to 99% yield and 96% ee. The air- and water-tolerant reaction conditions accommodate electronic and steric diversity of the aryldiazonium electrophile and of the tryptamine core.

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Cited by 2 publications

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Zinc Enolate/Sulfinate Prepared from a Single‐Run Reaction Using Zinc Dust with O‐Tosylated 4‐Hydroxy Coumarin and Pyrone

Zinc Enolate/Sulfinate Prepared from a Single‐Run Reaction Using Zinc Dust with O‐Tosylated 4‐Hydroxy Coumarin and Pyrone

Chiral Anion Phase Transfer of Aryldiazonium Cations: An Enantioselective Synthesis of C3‐Diazenated Pyrroloindolines

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