Rigidity to carbanion inversion of four-, five, six-membered cyclic organomagnesium compounds

Fraenkel, Gideon; Pechhold, Engelbert; Adams, David G.

doi:10.1021/jo00809a012

Cited by 16 publications

(1 citation statement)

References 4 publications

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“…[15a] Using our a-hydroxylation conditions,h ighly enantioenriched cyclopropanone equivalents 5a-5f were obtained in moderate to excellent yields as single diastereomers with retention of configuration at the a-position, as evidenced by X-ray crystallographic analysis (5a). [22][23][24] Theg eneral reactivity trend observed revealed that electron-poor substrates afford higher isolated yields in this transformation (e.g. 5d and 5e), with most reactions proceeding with complete retention of stereochemical information.…”

Section: Enantioselective Synthesis Of Cyclopropanone Equivalentsmentioning

confidence: 99%

Enantioselective Synthesis of Cyclopropanone Equivalents and Application to the Formation of Chiral β‐Lactams

et al. 2020

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Cyclopropanone derivatives have long been considered unsustainable synthetic intermediates because of their extreme strain and kinetic instability.R eported here is the enantioselective synthesis of 1-sulfonylcyclopropanols,a ss table yet powerful equivalents of the corresponding cyclopropanone derivatives,bya-hydroxylation of sulfonylcyclopropanes using ab is(silyl) peroxide as the electrophilic oxygen source. This work constitutes the first general approach to enantioenriched cyclopropanone derivatives.B oth the electronic and steric nature of the sulfonyl moiety,w hich serves as ab aselabile protecting group and confers crystallinity to these cyclopropanone precursors,w ere found to have ac rucial impact on the rate of equilibration to the corresponding cyclopropanone.T he utility of these cyclopropanone surrogates is demonstrated in amild and stereospecific formal [3+ +1] cycloaddition with simple hydroxylamines,l eading to the efficient formation of chiral b-lactam derivatives.

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Section: Enantioselective Synthesis Of Cyclopropanone Equivalentsmentioning

confidence: 99%

Enantioselective Synthesis of Cyclopropanone Equivalents and Application to the Formation of Chiral β‐Lactams

et al. 2020

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Study of the Configuration Stability of the Carbon – Zinc Bond, Direct Measurement of Enantiomeric Ratios, and Tentative Assignment of the Absolute Configuration in Secondary Organozinc Halides

Guijarro

Rieke

2000

Angewandte Chemie

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The determination of the stereochemical features of reactions involving organometallic species is a long-standing issue, which is still to be appropriately addressed. The study of the stereochemistry of products after a reaction of an organometallic species with a suitable electrophile has been the most commonly used strategy, [1] and often the only possible approach.[2] However the term ªsuitable electrophileº is intrinsically imprecise. The reaction of an organometallic reagent with an electrophile is always a possible source of interference when the goal is to study the organometallic compound itself. The degree of retention/inversion/ loss of stereochemical integrity is highly specific for each organometallic ± electrophile pair and is therefore not available in many cases. Different electrophiles can give rise to a different distribution of products with partial (or complete) retention (or inversion) of their configurations.[3] Even though retention of configuration is the most common reaction pathway, the exact behavior of each particular system is, at the present time, simply unpredictable. [4,5] Among the different organometallic reagents utilized in organic chemistry, organozinc compounds occupy an intermediate position in terms of the electronegativity of the metal and hence reactivity. As a general trend for organometallic reagents devoid of functionality, the more covalently bonded species are those which display high energy barriers to inversion of the carbon center (or topoisomerization barriers), [6] and vice versa. Thus, activation energies for inversion in primary organometallic compounds of the type R n M increase in the order M Li < Mg < Zn, and the inversion of Al and Hg compounds is slow on the NMR time scale. [7a,b] In general, NMR spectrometers are designed to operate between 200 8C and À 100 8C or less, which allows the study of a wide range of systems with activation energies ranging from approximately 5 to 25 kcal mol À1

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Study of the Configuration Stability of the Carbon – Zinc Bond, Direct Measurement of Enantiomeric Ratios, and Tentative Assignment of the Absolute Configuration in Secondary Organozinc Halides

Guijarro¹,

Rieke²

2000

Angew. Chem. Int. Ed.

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Rigidity to carbanion inversion of four-, five, six-membered cyclic organomagnesium compounds

Cited by 16 publications

References 4 publications

Enantioselective Synthesis of Cyclopropanone Equivalents and Application to the Formation of Chiral β‐Lactams

Enantioselective Synthesis of Cyclopropanone Equivalents and Application to the Formation of Chiral β‐Lactams

Study of the Configuration Stability of the Carbon – Zinc Bond, Direct Measurement of Enantiomeric Ratios, and Tentative Assignment of the Absolute Configuration in Secondary Organozinc Halides

Study of the Configuration Stability of the Carbon – Zinc Bond, Direct Measurement of Enantiomeric Ratios, and Tentative Assignment of the Absolute Configuration in Secondary Organozinc Halides

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