Asymmetric Catalysis via Cyclic, Aliphatic Oxocarbenium Ions

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Chemistry

Background:

• Oxygen heterocycles are prevalent in pharmaceuticals and natural products.
• Efficient enantioselective synthesis of these scaffolds remains a key challenge in organic chemistry.

Purpose of the Study:

• To develop a direct enantioselective synthetic route for substituted oxygen heterocycles.
• To utilize a novel imidodiphosphorimidate (IDPi) catalyst for this transformation.

Main Methods:

• Reaction of lactol acetates with enol silanes.
• Employing a highly reactive and confined imidodiphosphorimidate (IDPi) catalyst.
• Analysis of reaction products for enantioselectivity.

Main Results:

• Successful direct enantioselective synthesis of various oxygen heterocycles including tetrahydrofurans, tetrahydropyrans, oxepanes, chromans, and dihydrobenzofurans.
• Achieved excellent enantioselectivities for the synthesized chiral heterocycles.
• Mechanistic studies indicated a pathway involving a cyclic oxocarbenium ion intermediate.

Conclusions:

• The developed IDPi-catalyzed method provides an efficient access to enantiomerically enriched oxygen heterocycles.
• This methodology offers a valuable tool for the synthesis of complex chiral molecules.
• The confined chiral counteranion plays a crucial role in controlling enantioselectivity.