Asymmetric electrocyclic reactions

Thompson, Sam; Coyne, Anthony G.; Knipe, Peter C.; Smith, Martin D.

doi:10.1039/c1cs15022g

Cited by 76 publications

(39 citation statements)

References 183 publications

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“…Although pharma researchers now routinely and reliably separate enantiomers by preparative chiral HPLC (24,25), an asymmetric variant of the present reaction sequence could be contemplated through the use of chiral directing groups or asymmetric electrocylization catalysts (26,27). Moreover, the addition of many other types of nucleophiles should be possible, and the 1,2-dihydropyridine intermediates 4 could conceivably react with electrophiles other than proton to enable the regio- and stereoselective synthesis of even more densely substituted products.…”

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confidence: 99%

Proton Donor Acidity Controls Selectivity in Nonaromatic Nitrogen Heterocycle Synthesis

Duttwyler

Chen

Takase

et al. 2013

Science

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Piperidines are prevalent in natural products and pharmaceutical agents and are important synthetic targets for drug discovery and development. We report a methodology that provides highly substituted piperidine derivatives with regiochemistry selectively tunable by varying the strength of acid used in the reaction. Readily available starting materials are first converted to dihydropyridines via a cascade reaction initiated by rhodium-catalyzed C–H bond activation. Subsequent divergent regio- and diastereoselective protonation of the dihydropyridines under either kinetic or thermodynamic control provides two distinct iminium ion intermediates that then undergo highly diastereoselective nucleophilic additions. X-ray structural characterization of both the kinetically and thermodynamically favored iminium ions along with density functional theory calculations provide a theoretical underpinning for the high selectivities achieved for the reaction sequences.

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confidence: 99%

Proton Donor Acidity Controls Selectivity in Nonaromatic Nitrogen Heterocycle Synthesis

Duttwyler

Chen

Takase

et al. 2013

Science

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“…9 Herein, we describe the rational design and effective use of oxazoline auxiliaries that impose a significant bias for one of the two helical arrangements that lead to 8π electrocyclization.…”

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Asymmetric Induction in 8π Electrocyclizations. Design of a Removable Chiral Auxiliary

2011

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The pseudo C2 symmetric trans diphenyl oxazoline group acts as an effective chiral auxiliary in the 8π, 6π tandem electrocyclization of a substituted tetraene 1-carboxylic acid. Assignment of absolute stereochemistry to the [4.2.0] bicyclooctadiene product supports a model in which both s-cis and s-trans conformations favor the transition states with the same helical twist. This assignment prefaces the development of analogs of SNF4435 C and D. These natural products demonstrate activity as androgen receptor antagonists and as multidrug resistance (mdr) reversal agents.

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“…The general utility of the familiar Staudinger reaction of imines to transform readily accessible aldehydes to β-lactams has been well reviewed [30–33], yet in spite of this familiarity, the mechanism of this process remains a topic of interest [34–36]. …”

Section: Resultsmentioning

confidence: 99%

Diastereoselectivity in the Staudinger reaction of pentafluorosulfanylaldimines and ketimines

Penger¹,

Hahmann²,

Filatov³

et al. 2013

Beilstein J. Org. Chem.

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Summaryβ-Lactams were diastereoselectively formed by the reaction of SF5-containing aldimines, or an SF5-containing ketimine, with benzyloxyketene in a conrotatory ring closure process. Imine formation and cyclization were possible in spite of the acidification of protons on the carbon bound to SF5. The reactions of the aldimines demonstrated very good 1,2-lk diastereoselectivity, however lack of stereochemical control of the C–N ketimine geometry was reflected in the stereochemistry of the product β-lactam. Cyclization of imines with a stereogenic center bearing SF5 was reflected in the 1,2-lk,lk selectivity of the β-lactam.

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Asymmetric electrocyclic reactions

Abstract: This critical review offers an overview of asymmetric electrocyclic processes, where diastereo- or enantioselectivity is a consequence of the influence of a chiral component (be it substrate or catalyst) on the electrocyclic bond-forming process (195 references).

Cited by 76 publications

References 183 publications

Proton Donor Acidity Controls Selectivity in Nonaromatic Nitrogen Heterocycle Synthesis

Proton Donor Acidity Controls Selectivity in Nonaromatic Nitrogen Heterocycle Synthesis

Asymmetric Induction in 8π Electrocyclizations. Design of a Removable Chiral Auxiliary

Diastereoselectivity in the Staudinger reaction of pentafluorosulfanylaldimines and ketimines

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