Enantiodivergent Steglich rearrangement of O-carboxylazlactones catalyzed by a chirality switchable helicene containing a 4-aminopyridine unit

Chen, Chien‐Tien; Tsai, Ching‐Chih; Tsou, Pei-Kang; Huang, Gou-Tao; Yu, Chin‐Hui

doi:10.1039/c6sc02646j

Cited by 59 publications

(24 citation statements)

References 40 publications

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“…On the basis of previous reports,,, on the asymmetric Steglich rearrangement and our control experiments, a possible mechanism was proposed in Figure . Initially, chiral DMAP‐ N ‐oxide 13 a reacted with O‐acylated azlactone 15 a through a reversible nucleophilic acyl substitution, generating the ion‐pair intermediate, O‐acylated pyridinium cation I and enolate anion II .…”

Section: Figuresupporting

confidence: 53%

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Chiral DMAP‐N‐oxides as Acyl Transfer Catalysts: Design, Synthesis, and Application in Asymmetric Steglich Rearrangement

et al. 2019

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A DMAP‐N‐oxide, featuring an α‐amino acid as the chiral source, was developed, synthesized and applied in asymmetric Steglich rearrangement. A series of O‐acylated azlactones afforded C‐acylated azlactones possessing a quaternary stereocenter in high yields (up to 97 % yield) and excellent enantioselectivities (up to 97 % ee). Compared to the widespread use of pyridine nitrogen, which serves as the nucleophilic site in the asymmetric acyl transfer reaction, we discovered that chiral DMAP‐N‐oxides, in which the oxygen now acts as the nucleophilic site, are efficient acyl transfer catalysts. Our finding might open a new door for the development of chiral DMAP‐N‐oxides for asymmetric acyl transfer reactions.

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Section: Figuresupporting

confidence: 53%

“…The ‐CO 2 Ph group only afforded a moderate result, for which excellent results were obtained in the work of Smith et al . and in the Chen and Yu group . Considering the sterically hindered ‐CO 2 C(Me) 2 CCl 3 or ‐CO 2 CH 2 CCl 3 group has been achieved with excellent results by Smith et al .…”

Section: Figurementioning

confidence: 92%

Chiral DMAP‐N‐oxides as Acyl Transfer Catalysts: Design, Synthesis, and Application in Asymmetric Steglich Rearrangement

et al. 2019

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“…The Steglich rearrangement of O ‐carboxylazlactones 27 was reported by research groups of Yu and Suginome by employing chirality switchable helicene containing 4‐aminopyridine unit 4 f and helical poly(quinoxaline‐2,3‐diyl)s bearing achiral 4‐aminopyrid‐3‐yl pendants 4 g respectively. The reported protocols were concordant with earlier reports in obtaining rearranged product in high enantioselectivity (Scheme ) …”

Section: Pyridine Derivatives As Organocatalystssupporting

confidence: 90%

Recent Advances in Pyridine‐Based Organocatalysis and its Application towards Valuable Chemical Transformations

2020

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The role of pyridine scaffolds in the field of synthetic organic and medicinal chemistry is impeccable and irreplaceable due to its wide spectrum of applications. Pyridines are well known for their usage as bases and to some extent they have been employed as ligands. In recent times, pyridine scaffolds are explored as organocatalysts to accomplish various novel chemical transformations. Here in this review, we have focused on highlighting the protocols available to accomplish wide range of chemical modulations employing different pyridine moieties as organocatalysts for various reactions such as reductive borylation, acylation, heterocyclization and additions to carbonyl derivatives. The application of organocatalysis in the fields of kinetic resolution and desymmetrization are also been presented

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“…Chiral N , N ‐dimethylaminopyridine (DMAP) derivatives have attracted attention as asymmetric nucleophilic catalysts for stereoselective acylations in kinetic resolution of chiral alcohols and amines, as well as desymmetrization of meso ‐diols . DMAP derivatives possessing central chirality have been well developed; however, only a few DMAP derivatives bearing molecular asymmetry such as axial chirality, planer chirality, and other miscellaneous chirality have been investigated.…”

Section: Introductionmentioning

confidence: 99%

Axial chirality in biaryl N,N‐dialkylaminopyridine derivatives bearing an internal carboxy group

et al. 2020

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Axial chirality in N,N-dimethylaminopyridines as well as N,Ndipropylaminopyridines bearing an internal carboxy group were evaluated based on their racemization barriers and circular dichroism spectra. The halflife of racemization of N,N-dipropylaminopyridine derivative 2 was estimated to be 19.7 days at 20 C. Its enantiomers isolated as optically active forms showed positive-negative and negative-positive Cotton effects for (+)-2 and (−)-2, respectively, from 310 to 210 nm. Furthermore, (−)-2 was applied as a chiral nucleophilic catalyst and exhibited asymmetric induction in acylative kinetic resolution of 1-(1-naphthyl)ethane-1-ol. K E Y W O R D Saxial chirality, circular dichroism acylative kinetic resolution, DMAP derivative

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Enantiodivergent Steglich rearrangement of O-carboxylazlactones catalyzed by a chirality switchable helicene containing a 4-aminopyridine unit

Abstract: Chirality-switchable, 4-aminopyridine-based, pseudo-enantiomeric helicenes can catalyze enantiodivergent Steglich rearrangement in up to 91% ee (R) and 94% ee (S), respectively.

Cited by 59 publications

References 40 publications

Chiral DMAP‐N‐oxides as Acyl Transfer Catalysts: Design, Synthesis, and Application in Asymmetric Steglich Rearrangement

Chiral DMAP‐N‐oxides as Acyl Transfer Catalysts: Design, Synthesis, and Application in Asymmetric Steglich Rearrangement

Recent Advances in Pyridine‐Based Organocatalysis and its Application towards Valuable Chemical Transformations

Axial chirality in biaryl N,N‐dialkylaminopyridine derivatives bearing an internal carboxy group

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