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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
Published on: February 6, 2019
Discovery and Development of a Three-Component Oxidopyrylium [5 + 2] Cycloaddition
Michael P D'Erasmo1,2, Christine Meck1,2, Chad A Lewis3
1Department of Chemistry, Brooklyn College, The City University of New York , Brooklyn, New York 11210, United States.
New oxidopyrylium cycloaddition reactions using ethanol-stabilized chloroform generate novel α-ethoxyenone bicyclic products. This optimized three-component process offers a convenient route to diverse oxabicyclo[3.2.1]octane structures and α-hydroxytropolones.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
Background:
- α-Hydroxy-γ-pyrone-based oxidopyrylium cycloaddition reactions provide access to diverse oxabicyclo[3.2.1]octane scaffolds.
- Intermolecular reactions typically yield α-methoxyenone products via a pre-ylide salt intermediate.
Purpose of the Study:
- To explore the use of ethanol-stabilized chloroform as a solvent in oxidopyrylium cycloaddition reactions.
- To develop an optimized three-component process for generating α-ethoxyenone-containing bicyclic byproducts.
- To demonstrate a tandem ring-opening/debenzylation method for α-hydroxytropolone synthesis.
Main Methods:
- Utilizing ethanol-stabilized chloroform as a solvent in oxidopyrylium cycloaddition reactions.
- Optimizing a three-component process involving a pre-heated oxidopyrylium dimer and alcohol with a dipolarophile.
- Applying the method to a tandem ring-opening/debenzylation sequence.
Main Results:
- Discovery of α-ethoxyenone-containing bicyclic byproducts when using ethanol-stabilized chloroform.
- Successful optimization of the three-component cycloaddition through gentle heating.
- Generation of several new oxidopyrylium cycloaddition products in moderate yields.
- Demonstration of the method for synthesizing α-hydroxytropolones.
Conclusions:
- Ethanol-stabilized chloroform serves as an effective solvent for generating α-ethoxyenone bicyclic products via oxidopyrylium cycloaddition.
- The optimized three-component process is a convenient method for synthesizing diverse oxabicyclo[3.2.1]octane derivatives.
- The developed methodology facilitates the synthesis of valuable α-hydroxytropolones.
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