Highly selective insertion of arynes into a C(sp)-O(sp3) σ bond

Area of Science:

• Organic Chemistry
• Reaction Mechanism Studies

Background:

• Arynes are highly reactive intermediates in organic synthesis.
• Ethoxyacetylene is a valuable building block for introducing ethoxyethynyl groups.
• Previous mechanistic proposals for aryne-alkyne cycloadditions require re-evaluation.

Purpose of the Study:

• To investigate the reaction between arynes and ethoxyacetylene.
• To elucidate the chemoselectivity and regioselectivity of the observed formal insertion.
• To determine the accurate reaction mechanism using computational methods.

Main Methods:

• Experimental reaction of arynes with ethoxyacetylene.
• Isolation and characterization of 2-ethoxyethynylaryl derivatives.
• Density Functional Theory (DFT) calculations to model reaction pathways.

Main Results:

• Successful synthesis of 2-ethoxyethynylaryl derivatives via formal insertion.
• High chemo- and regioselectivity observed in the aryne-alkyne reaction.
• Computational studies disproved nucleophilic oxygen addition, supporting triple bond addition to the aryne.

Conclusions:

• The reaction represents a novel route to functionalized aryl compounds.
• The mechanism proceeds via direct addition of the ethoxyacetylene triple bond to the aryne.
• This finding corrects previous mechanistic assumptions and provides new insights into aryne chemistry.