Gold(I)/(III)-Catalyzed Synthesis of Cyclic Ethers; Valency-Controlled Cyclization Modes

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Propargylic alcohols are versatile precursors in organic synthesis.
• Gold catalysis has emerged as a powerful tool for various organic transformations.
• Selective synthesis of cyclic ethers remains a key challenge in organic chemistry.

Purpose of the Study:

• To explore the distinct reactivity of oxophilic gold(III) and π-philic gold(I) catalysts.
• To develop selective synthetic routes to different classes of cyclic ethers from propargylic alcohols.
• To elucidate the reaction mechanisms governing these transformations.

Main Methods:

• Utilizing gold(III) catalysts (e.g., AuBr3) for direct cyclization.
• Employing gold(I) catalysts (e.g., Ph3PAuNTf2) to initiate Meyer-Schuster rearrangement.
• Investigating intramolecular oxa-Michael addition pathways.

Main Results:

• Gold(III) catalysis yields cyclic ethers with acetylenic moieties via hydroxyl group coordination.
• Gold(I) catalysis leads to α,β-unsaturated ketones, which then form carbonyl-containing cyclic ethers through gold(III)-catalyzed oxa-Michael addition.
• The choice of gold catalyst dictates the structure of the resulting cyclic ether.

Conclusions:

• Strategic application of gold(I) and gold(III) catalysts enables divergent synthesis of cyclic ethers.
• This methodology provides access to valuable cyclic ether scaffolds with distinct functional groups.
• The findings offer new insights into the mechanistic pathways of gold-catalyzed reactions.