NMR Spectroscopic Investigation of the Adducts Formed by Addition of Cuprates to Ynoates and Ynones: Alkenylcuprates or Allenolates?

Nilsson, Karolina; Andersson, Thomas; Ullenius, Christina; Gerold, Andreas; Krause, Norbert

doi:10.1002/(sici)1521-3765(19981002)4:10<2051::aid-chem2051>3.3.co;2-6

Cited by 21 publications

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“…Much more recently Krause4e utilized NMR analysis and concluded that two copper allenolates are the species resulting from Michael addition with the copper coordinating differently but intramolecularly with the allenic system. Subsequently, Ullenius and Krause4f have suggested that both vinylcopper and copper allenolates are accessible depending on the reagents used. It was suggested that protonation of allenolates proceeded unselectively in the cases studied.…”

Section: Introductionmentioning

confidence: 99%

The Stereochemistry of Allenic Enol Tautomerism – Independent Generation and Reactivity of the Enolates

Zimmerman

Pushechnikov

2006

Eur J Org Chem

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A priori, allenic enolates as reaction intermediates may be protonated to afford (Z)‐ or (E)‐α,β‐unsaturated carbonyl products. The allenic enolates are tautomeric with α‐vinylcarbanions. The literature on the behavior of these species on protonation is highly varied both in stereochemical outcome and in mechanistic interpretation. The current study has provided an independent mode of generation of the allenic enolates and has investigated the reaction stereochemistry of protonation to afford the stereoisomeric α,β‐unsaturated carbonyl products. Under kinetic conditions, these highly reactive species are protonated in the α,β‐π plane with preference (E) to the larger β group. Under thermodynamic conditions, addition/elimination equilibrates the two product stereoisomers. The kinetic protonation stereochemistry is a function of solvent, proton donor, and donor concentration. Computations serve to clarify the reaction mechanism. It was found that the stereochemistry of ketonization of allenic enolates follows the reaction course suggested as possible some decades earlier and common to less unique enolates. Additionally, the linear versus the bent enolate structure proves to depend on the countercation.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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Section: Introductionmentioning

confidence: 99%

The Stereochemistry of Allenic Enol Tautomerism – Independent Generation and Reactivity of the Enolates

Zimmerman

Pushechnikov

2006

Eur J Org Chem

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“…The minor occurrence of anti -addition is likely due to the geometrical isomerization of the alkenylcopper species ( D / D' ) through a copper(I) allenoate complex ( E , Fig. 2 ) [ 15 , 26 ]. The resulting allenoate E can undergo protonolysis to form either syn - 4 or anti - 4 depending on the substituent effects of R 1 and R 2 , while the isomerized alkenylcopper(I) D' should preferentially yield anti - 4 .…”

Section: Resultsmentioning

confidence: 99%

Copper-catalyzed stereoselective conjugate addition of alkylboranes to alkynoates

Wakamatsu¹,

Nagao²,

Ohmiya³

et al. 2015

Beilstein J. Org. Chem.

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SummaryA copper-catalyzed conjugate addition of alkylboron compounds (alkyl-9-BBN, prepared by hydroboration of alkenes with 9-BBN-H) to alkynoates to form β-disubstituted acrylates is reported. The addition occurred in a formal syn-hydroalkylation mode. The syn stereoselectivity was excellent regardless of the substrate structure. A variety of functional groups were compatible with the conjugate addition.

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“…Formation of anti ‐adducts anti ‐ 7 and anti ‐ 8 can be explained by a reaction of organic electrophiles with anti ‐alkenylcuprate anti ‐ 9 generated by an isomerization from syn ‐ 9 via an allenolate intermediate 10 . An allenolate‐type intermediate for the isomerization of alkenylcopper species has been proposed based on NMR spectroscopy18 and DFT calculation 19. Thus, the results in Table 1 could be explained as follows: 1) At low temperature, syn ‐alkenylcuprate intermediate syn ‐ 9 reacted with unhindered allyl bromide affording the syn adduct (entry 3) and did not react with relatively bulky benzoyl chloride (entry 1).…”

Section: Methodsmentioning

confidence: 99%

One‐Step Lactosylation of Hydrophobic Alcohols by Nonaqueous Biocatalysis

et al. 2010

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SEE delights: Alkyllactosides are successfully synthesized in a one‐step enzymatic reaction from lactose in its original form and hydrophobic alcohols, by using a surfactant‐enveloped enzyme (SEE) in nonaqueous 1,3‐dimethyl‐2‐imidazolizinone, which can dissolve both donor sugars and acceptors. Nonaqueous biocatalysis is highly advantageous for efficient enzymatic glycosylation by SEE‐mediated dehydration reaction.

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NMR Spectroscopic Investigation of the Adducts Formed by Addition of Cuprates to Ynoates and Ynones: Alkenylcuprates or Allenolates?

Cited by 21 publications

References 0 publications

The Stereochemistry of Allenic Enol Tautomerism – Independent Generation and Reactivity of the Enolates

The Stereochemistry of Allenic Enol Tautomerism – Independent Generation and Reactivity of the Enolates

Copper-catalyzed stereoselective conjugate addition of alkylboranes to alkynoates

One‐Step Lactosylation of Hydrophobic Alcohols by Nonaqueous Biocatalysis

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