Remote Functionalization by Pd-Catalyzed Isomerization of Alkynyl Alcohols

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Alkene isomerization is well-established for remote functionalization.
• Catalytic methods for alkyne isomerization remain less developed.
• Alkynyl alcohols are versatile synthetic precursors.

Purpose of the Study:

• To develop a general palladium-catalyzed method for long-range alkyne isomerization.
• To access α,β-unsaturated aldehydes from alkynyl alcohols.
• To investigate the mechanism of the isomerization process.

Main Methods:

• Palladium-catalyzed isomerization of aryl-, heteroaryl-, and alkyl-substituted alkynyl alcohols.
• Optimization of reaction conditions for yield and selectivity.
• Computational studies (e.g., DFT) to elucidate reaction mechanism.

Main Results:

• A general Pd-catalyzed method for long-range isomerization of alkynyl alcohols was established.
• The reaction preferentially yielded thermodynamically stable α,β-unsaturated aldehydes.
• The catalytic system demonstrated compatibility with sensitive functional groups.
• Migration of both π-components of the alkyne over several methylene units was achieved.
• An unorthodox phosphine-assisted deprotonation mechanism was proposed for the final tautomerization step.

Conclusions:

• The developed method offers a novel route to α,β-unsaturated aldehydes via alkyne isomerization.
• The study expands the scope of remote functionalization strategies.
• Mechanistic insights reveal unique catalytic pathways, including phosphine-assisted deprotonation.