The rhodium-catalyzed formal C（sp^3）-H activation/spiroannulation of α-arylidene pyrazolones with alkynes was investigated by means of density functional theory calculations. The calculations indicate that the spir...The rhodium-catalyzed formal C（sp^3）-H activation/spiroannulation of α-arylidene pyrazolones with alkynes was investigated by means of density functional theory calculations. The calculations indicate that the spiroannulation through the proposed C-C reductive elimination is kinetically unfeasible, Instead, the C-C coupling from the eight-membered rhodacycle was proposed to account for the experimental results. The overall catalytic cycle consists of six steps： （1） the keto-enol isomerization; （2） the O-H deprotonation, （3） the C（sp^2）-H bond cleavage; （4） the migratory insertion of alkyne into the Rh-C bond; （5） the C-C coupling and （6） the regeneration of the active catalyst.展开更多
Atom-and step-economy in IBX assisted diversity-oriented synthesis is achieved with a versatile AQ auxiliary α-amino acid analogs offering rapid access to polycyclic spiro-quinolines featuring a quaternary stereocent...Atom-and step-economy in IBX assisted diversity-oriented synthesis is achieved with a versatile AQ auxiliary α-amino acid analogs offering rapid access to polycyclic spiro-quinolines featuring a quaternary stereocenter in 20%–91% yields under mild conditions via 7,8-dearomatization of quinolines. Free of a preinstalled activation group is highlight of this intramolecular oxidation spiroannulation tandem reaction. This type of N-heterospirocycles, traditionally difficult to access, may open the door to a potentially interest scaffold for synthetic and medicinal chemistry.展开更多
An enantioselective[4+1]spiroannulation ofαbromo-β-naphthols with azoalkenes has been developed for the one-step construction of a new class of pyrazoline-based spirocyclic molecules.Using chiral Cu(II)/Box catalyst...An enantioselective[4+1]spiroannulation ofαbromo-β-naphthols with azoalkenes has been developed for the one-step construction of a new class of pyrazoline-based spirocyclic molecules.Using chiral Cu(II)/Box catalysts,asymmetric induction was achieved with high levels of enantioselectivity[up to 99:1 enantiomeric ratio(er)].Notably,α-chloroandα-iodo-substitutedβ-naphthols were also tolerated by this reaction.Mechanistic studies disclosed that this process was triggered by electrophilefacilitated dearomatization ofα-bromo-β-naphthols and followed by the debromination via SRN 1-subsitution with in situ-formed N-nucleophile.The chiral copper(II)-species,bound with azoalkene moiety,was assumed to control the enantiodiscrimination over the naphthoxy C-radical that was generated from the debromination step.Moreover,the potential utility of this protocol was greatly amplified by the derivatization of spirocyclic products through oxidative dearomatization of the other aromatic ring in the naphthyl fragment,providing a rather attractive route for the rapid generation of synthetically more valuable doubly dearomatized architectures.展开更多
基金supported by the National Natural Science Foundation of China(No.21503143)the Tianjin Natural Science Foundation(Nos.16JCQNJC05600 and 16JCYBJC43600)+1 种基金the Talent Research Start-up Fund of Tianjin Normal University(No.5RL139)support from the Shenzhen Peacock Plan(No.1208040050847074)
文摘The rhodium-catalyzed formal C（sp^3）-H activation/spiroannulation of α-arylidene pyrazolones with alkynes was investigated by means of density functional theory calculations. The calculations indicate that the spiroannulation through the proposed C-C reductive elimination is kinetically unfeasible, Instead, the C-C coupling from the eight-membered rhodacycle was proposed to account for the experimental results. The overall catalytic cycle consists of six steps： （1） the keto-enol isomerization; （2） the O-H deprotonation, （3） the C（sp^2）-H bond cleavage; （4） the migratory insertion of alkyne into the Rh-C bond; （5） the C-C coupling and （6） the regeneration of the active catalyst.
基金the National Natural Science Foundation of China (Nos. 22101074, 21877206, and 21772032)the 111 Project (No. D17007)+2 种基金Excellent Youth Foundation of Henan Scientific Committee (No. 222300420012)China Postdoctoral Science Foundation (No. 2019M660173)the Natural Science Foundation of Henan Province (No. 202300410233)。
文摘Atom-and step-economy in IBX assisted diversity-oriented synthesis is achieved with a versatile AQ auxiliary α-amino acid analogs offering rapid access to polycyclic spiro-quinolines featuring a quaternary stereocenter in 20%–91% yields under mild conditions via 7,8-dearomatization of quinolines. Free of a preinstalled activation group is highlight of this intramolecular oxidation spiroannulation tandem reaction. This type of N-heterospirocycles, traditionally difficult to access, may open the door to a potentially interest scaffold for synthetic and medicinal chemistry.
基金supported by the National Natural Science Foundation of China(nos.21925108 and 21901203)the Key Science and Technology Innovation Team of Shaanxi(no.2017KCT-37)+1 种基金the Key Laboratory Project of Xi’an(no.201805058ZD9CG42)the Education Department of Shaanxi Province(nos.18JS108 and 20JK0934).
文摘An enantioselective[4+1]spiroannulation ofαbromo-β-naphthols with azoalkenes has been developed for the one-step construction of a new class of pyrazoline-based spirocyclic molecules.Using chiral Cu(II)/Box catalysts,asymmetric induction was achieved with high levels of enantioselectivity[up to 99:1 enantiomeric ratio(er)].Notably,α-chloroandα-iodo-substitutedβ-naphthols were also tolerated by this reaction.Mechanistic studies disclosed that this process was triggered by electrophilefacilitated dearomatization ofα-bromo-β-naphthols and followed by the debromination via SRN 1-subsitution with in situ-formed N-nucleophile.The chiral copper(II)-species,bound with azoalkene moiety,was assumed to control the enantiodiscrimination over the naphthoxy C-radical that was generated from the debromination step.Moreover,the potential utility of this protocol was greatly amplified by the derivatization of spirocyclic products through oxidative dearomatization of the other aromatic ring in the naphthyl fragment,providing a rather attractive route for the rapid generation of synthetically more valuable doubly dearomatized architectures.
