Lithium tert-butoxide-mediated efficient transesterification of N-hydroxyphthalimide esters toward oxime...

Area of Science:

• Organic Chemistry
• Synthetic Methodology

Background:

• Oxime esters are valuable synthetic intermediates.
• Efficient and mild methods for oxime ester synthesis are needed.

Purpose of the Study:

• To develop a novel, transition-metal-free method for oxime ester synthesis.
• To explore the utility of lithium tert-butoxide in transesterification reactions.

Main Methods:

• Lithium tert-butoxide (LiO^tBu)-mediated transesterification of N-hydroxyphthalimide (NHPI) esters with oximes.
• Reaction optimization and mechanistic studies including DFT calculations.

Main Results:

• High yields (up to 99%) of oxime esters achieved under mild conditions.
• The method demonstrates broad substrate scope and high chemoselectivity.
• LiO^tBu facilitates the reaction via a nucleophilic oximate intermediate and lithium-assisted chelation.

Conclusions:

• A simple, efficient, and scalable transition-metal-free synthesis of oxime esters is established.
• The Lewis acidity of Li+ is key to the reaction mechanism.
• This method provides a practical route to diverse oxime ester derivatives.