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  Two Enabling Strategies for the Stereoselective Conversion of Internal Alkynes into Trisubstituted Alkenes

Huwyler, N., Radkowski, K., Rummelt, S. M., & Fürstner, A. (2017). Two Enabling Strategies for the Stereoselective Conversion of Internal Alkynes into Trisubstituted Alkenes. Chemistry – A European Journal, 23(50), 12412-12419. doi:10.1002/chem.201702470.

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Huwyler, Nikolas1, Author              
Radkowski, Karin1, Author              
Rummelt, Stephan M.1, Author              
Fürstner, Alois1, Author              
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1Research Department Fürstner, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445584              

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Free keywords: alkenes; alkynes; copper; hydrometalation; ruthenium; silicon; tin
 Abstract: An expedient method for the C-methylation of alkenylstannanes with formation of trisubstituted alkenes is described, which relies on the use of MeI in combination with copper thiophene-2-carboxylate (CuTC) as promotor and tetra-n-butylammonium diphenylphosphinate as an effective tin scavenger; in some cases, it proved beneficial to further supplement the mixture with catalytic amounts of Pd(PPh3)4. Under these conditions, the reaction is robust, high yielding, and compatible with many functional groups that might not subsist under more traditional conditions used to C-alkylate organotin derivatives. A qualitative analysis of the reaction profile suggested that the in situ formation of a reactive organocopper intermediate and its interception by MeI is only barely faster than O-methylation of the phosphinate additive by the same alkylating agent. To guarantee high yields and prevent net protodestannation from occurring, the reaction protocol had to be optimized such that these competing processes are properly decoupled. The new method is particularly well suited for the stereoselective preparation of the (E)-2-methylbut-2-en-1-ol motif that is present in numerous natural products. Alternatively, this particular target structure can be accessed starting from α-hydroxy alkenylsiloxane precursors, which get C-methylated upon exposure to CuI/LiOtBu and MeI by what is thought to be a Brook rearrangement/ alkylation sequence. The required substrates are best prepared by ruthenium-catalyzed trans-hydrosilylation or trans-hydrostannation of propargyl alcohols.

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Language(s): eng - English
 Dates: 2017-05-302017-07-172017-08-042017-09-07
 Publication Status: Published in print
 Pages: 8
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1002/chem.201702470
 Degree: -

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Title: Chemistry – A European Journal
  Other : Chem. – Eur. J.
  Other : Chem. Eur. J.
Source Genre: Journal
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Publ. Info: Weinheim, Germany : VCH Verlagsgesellschaft
Pages: - Volume / Issue: 23 (50) Sequence Number: - Start / End Page: 12412 - 12419 Identifier: ISSN: 0947-6539
CoNE: https://pure.mpg.de/cone/journals/resource/954926979058