Computational and Experimental Studies into Photoenamination/Diels-Alder Reactions

Area of Science:

• Organic Chemistry
• Photochemistry
• Reaction Mechanisms

Background:

• The photoenolization/Diels-Alder (oxa-PEDA) reaction has broad applications, but its nitrogen analog, aza-PEDA, is limited to N-silylimines.
• Understanding the mechanistic limitations of aza-PEDA is crucial for expanding its synthetic utility.

Purpose of the Study:

• To investigate the mechanistic challenges hindering the broader application of the aza-PEDA reaction.
• To computationally and experimentally expand the scope of aza-PEDA beyond N-silylimines.

Main Methods:

• Computational studies to analyze reaction pathways and energy barriers.
• Experimental investigations of imine precursors and reaction conditions.
• Reevaluation of the aza-PEDA mechanism on the singlet manifold.

Main Results:

• Identified key hurdles in the aza-PEDA mechanism compared to oxa-PEDA, including less favorable 1,5-hydrogen atom transfer, unfavorable conformations, and radiationless decay.
• Observed alternative pathways like N-S bond cleavage in N-tosylimine precursors.
• Successfully extended aza-PEDA reactions to N-methanesulfonylimine derivatives.

Conclusions:

• The aza-PEDA reaction faces unique challenges due to the nitrogen heteroatom.
• Overcoming these challenges allows for the development of new synthetic methodologies using aza-PEDA reactions.