Rare, Neglected and Potential Synthetic Methods for the Separation of Enantiomers

Todd, Matthew H.

doi:10.1002/9783527650880.ch7

Cited by 1 publication

(3 citation statements)

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“…Studies to get more mechanistic details of this robust kinetic resolution protocol were conducted. It has been well documented in literature reports that almost all currently known KRs are realized in only one key step or in the first step between racemates and resolution partners (for cascade reaction-mediated resolutions) . In other words, the enantio-discriminating and the unreacted enantiomer releasing are completed within one single step.…”

Section: Mechanistic Studiesmentioning

confidence: 99%

“…Catalytic kinetic resolution (KR) represents a valuable technique for obtaining extremely high levels of enantioenrichment in an unreacted substrate through high selectivity factors ( s ) and control of conversion . In this context, a powerful KR protocol accessing enantiopure α-functionalized ketones is supposed to show high generality to different substituent types using the same set of reaction conditions, which will also be an ideal approach.…”

Section: Introductionmentioning

confidence: 99%

“…However, to guarantee high resolution efficiency, a series of key challenges must be addressed: (1) an initial reversible Michael addition is vital for the recovery of the enantioenriched substrates, because in this step, the kinetic resolution is hard to be realized owing to the remote stereoinduction between the catalyst and the ketone α-position; (2) the resolution step is supposed to occur at the following aldol process, and the enantiodiscrimination must be excellent to achieve high resolution efficiency; (3) the unreacted Michael adducts must undergo a very efficient retro-Michael reaction to release the enantioenriched α-functionalized ketones; (4) the basic reaction conditions should not lead to racemization of the enantioenriched ketones. To the best of our knowledge, all known KR processes occur within one single step or the first step between the racemates and the resolution partners; therefore, if successful, the above design represents a conceptually new resolution mode and will provide new possibilities to solve the challenges that could not be addressed using direct one-step resolution methods.…”

Section: Introductionmentioning

confidence: 99%

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Organocatalyzed Kinetic Resolution of α-Functionalized Ketones: The Malonate Unit Leads the Way

et al. 2020

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Developing a catalytic kinetic resolution (KR) protocol affording enantioenriched α-functionalized ketones with broad substrate scope and high efficiency has been a longstanding challenge. Here, we report a successful protocol toward addressing this issue via an organocatalyzed cascade annulation. The protocol could afford 11 classes of enantioenriched α-functionalized ketones using a single catalytic system and avoid the frequent alterations of reaction conditions used in conventional methods. Up to 684 of the selectivity factor (s) is observed, and in most case, the s values are higher than 100. An aminolactam additive proves essential in promoting the resolution efficiency. Moreover, many previously unavailable enantiopure α-functionalized ketones are now accessible, and the annulation products are also useful building blocks and can be further transferred to densely substituted ketones without erosion of the optical purity. Mechanistically, in sharp contrast to the currently used direct one-step resolution patterns, a two-key-step resolution mode, wherein the enantiomer discrimination happens at the second aldol step and the enatioenriched ketones are recovered by the reversible initial Michael reaction, is proposed, which provides opportunities addressing the challenging tasks that could not be solved by conventional resolution techniques.

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Section: Mechanistic Studiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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