β-Aminocarbonates in Regioselective and Ring Expansion Reactions.

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Reaction Mechanism Studies

Background:

• β-aminocarbonates serve as versatile building blocks in organic synthesis.
• Understanding their reactivity as electrophiles is crucial for developing new synthetic methodologies.
• Alkylation reactions with phenols are fundamental transformations in medicinal and materials chemistry.

Purpose of the Study:

• To investigate the reactivity of β-aminocarbonates as anisotropic electrophiles with various phenols.
• To elucidate the factors governing the regioselectivity of anchimerically driven alkylation reactions.
• To explore the stereoselective synthesis of optically active 3-substituted piperidines.

Main Methods:

• Reactions of β-aminocarbonates with a range of phenols.
• Analysis of product distribution to determine regioselectivity.
• Utilizing enantiomerically pure pyrrolidine-based carbonates for stereochemical investigations.
• Confirmation of structures and stereochemistry using Nuclear Magnetic Resonance (NMR) spectroscopy and X-ray diffraction analysis.

Main Results:

• Regioselectivity of the alkylation reaction is dependent on the nature of the nucleophile.
• Reactions under thermodynamic control favor attack at the most sterically hindered carbon of the cyclic aziridinium intermediate when nucleophiles are good leaving groups.
• Stereoselective synthesis of optically active 3-substituted piperidines was achieved via a bicyclic aziridinium intermediate using enantiomerically pure pyrrolidine-based carbonates.

Conclusions:

• β-aminocarbonates exhibit controllable regioselectivity in alkylation reactions with phenols.
• The reaction mechanism transitions between kinetic and thermodynamic control based on nucleophile properties.
• This work provides a novel route for the stereoselective synthesis of valuable piperidine derivatives.