Vinylidene Homologation of Boronic Esters and its Application to the Synthesis of the Proposed Structure of Machillene

James M Fordham, Matthew N Grayson, Varinder Kumar Aggarwal

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Abstract

Alkenyl boronic esters are important reagents in organic synthesis. Herein, we report that these valuable products can be accessed by the homologation of boronic esters with a lithiated epoxysilane. Aliphatic and electron-rich aromatic boronic esters provided vinylidene boronic esters in moderate to high yields, while electron-deficient aromatic and vinyl boronic esters were found to give the corresponding vinyl silane products. Through DFT calculations, this divergence in mechanistic pathway has been rationalized by considering the stabilization of negative charge in the transition state of the elimination step. This vinylidene homologation was used in a short six step stereoselective synthesis of the proposed structure of machillene, however, synthetic and reported data were found to be inconsistent.

Original languageEnglish
JournalAngewandte Chemie-International Edition
Early online date31 Jul 2019
DOIs
Publication statusE-pub ahead of print - 31 Jul 2019

Cite this

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title = "Vinylidene Homologation of Boronic Esters and its Application to the Synthesis of the Proposed Structure of Machillene",
abstract = "Alkenyl boronic esters are important reagents in organic synthesis. Herein, we report that these valuable products can be accessed by the homologation of boronic esters with a lithiated epoxysilane. Aliphatic and electron-rich aromatic boronic esters provided vinylidene boronic esters in moderate to high yields, while electron-deficient aromatic and vinyl boronic esters were found to give the corresponding vinyl silane products. Through DFT calculations, this divergence in mechanistic pathway has been rationalized by considering the stabilization of negative charge in the transition state of the elimination step. This vinylidene homologation was used in a short six step stereoselective synthesis of the proposed structure of machillene, however, synthetic and reported data were found to be inconsistent.",
author = "Fordham, {James M} and Grayson, {Matthew N} and Aggarwal, {Varinder Kumar}",
note = "{\circledC} 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.",
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T1 - Vinylidene Homologation of Boronic Esters and its Application to the Synthesis of the Proposed Structure of Machillene

AU - Fordham, James M

AU - Grayson, Matthew N

AU - Aggarwal, Varinder Kumar

N1 - © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

PY - 2019/7/31

Y1 - 2019/7/31

N2 - Alkenyl boronic esters are important reagents in organic synthesis. Herein, we report that these valuable products can be accessed by the homologation of boronic esters with a lithiated epoxysilane. Aliphatic and electron-rich aromatic boronic esters provided vinylidene boronic esters in moderate to high yields, while electron-deficient aromatic and vinyl boronic esters were found to give the corresponding vinyl silane products. Through DFT calculations, this divergence in mechanistic pathway has been rationalized by considering the stabilization of negative charge in the transition state of the elimination step. This vinylidene homologation was used in a short six step stereoselective synthesis of the proposed structure of machillene, however, synthetic and reported data were found to be inconsistent.

AB - Alkenyl boronic esters are important reagents in organic synthesis. Herein, we report that these valuable products can be accessed by the homologation of boronic esters with a lithiated epoxysilane. Aliphatic and electron-rich aromatic boronic esters provided vinylidene boronic esters in moderate to high yields, while electron-deficient aromatic and vinyl boronic esters were found to give the corresponding vinyl silane products. Through DFT calculations, this divergence in mechanistic pathway has been rationalized by considering the stabilization of negative charge in the transition state of the elimination step. This vinylidene homologation was used in a short six step stereoselective synthesis of the proposed structure of machillene, however, synthetic and reported data were found to be inconsistent.

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DO - 10.1002/anie.201907617

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JO - Angewandte Chemie-International Edition

JF - Angewandte Chemie-International Edition

SN - 1433-7851

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