Triethylborane-induced intermolecular radical addition to ketimines

Area of Science:

• Organic Chemistry
• Radical Reactions
• Synthetic Methodology

Background:

• Intermolecular carbon radical addition reactions are crucial for C-C bond formation.
• Ketimines serve as versatile electrophilic partners in organic synthesis.
• Developing efficient and selective radical addition methods to ketimines remains an active research area.

Purpose of the Study:

• To investigate the intermolecular carbon radical addition to ketimines.
• To identify effective radical acceptors and reaction conditions.
• To explore the stereoselectivity of the radical addition to chiral ketimines.

Main Methods:

• Utilized triethylborane as a radical initiator for intermolecular carbon radical addition.
• Screened various potential radical acceptors, including pyruvic hydrazone and isatin hydrazone.
• Investigated reactions under different conditions, including aqueous media and in the presence of Lewis acids (BF(3).OEt(2)).

Main Results:

• Pyruvic hydrazone (3) and isatin hydrazone (7) demonstrated significant reactivity towards nucleophilic alkyl radicals.
• The radical addition reactions proceeded efficiently under aqueous-medium conditions for substrates 3 and 7.
• Radical addition to a chiral ketimine (11) in the presence of BF(3).OEt(2) yielded products with good diastereoselectivities.

Conclusions:

• Triethylborane effectively initiates intermolecular carbon radical addition to ketimines.
• Pyruvic and isatin hydrazones are highly reactive radical acceptors, suitable for aqueous conditions.
• The developed method allows for diastereoselective radical addition to chiral ketimines, expanding synthetic utility.