Syn vs. Anti? What Controls Addition Stereochemistry in Chlorolactonization

Area of Science:

• Organic Chemistry
• Reaction Mechanisms
• Stereochemistry

Background:

• Understanding the stereochemical outcomes of organic reactions is crucial for synthetic chemistry.
• Chlorolactonization is a key reaction for forming cyclic compounds with specific stereochemistry.

Purpose of the Study:

• To investigate the intrinsic diastereoselectivities of uncatalyzed chlorolactonization of 4-phenylpent-4-enoic acid.
• To elucidate the reaction mechanism, including syn and anti alkene addition pathways.
• To identify factors influencing stereocontrol in halofunctionalization reactions.

Main Methods:

• Kinetic studies utilizing Variable Time Normalization Analysis (VTNA).
• Quantum chemical modeling to support mechanistic interpretations.
• Examination of stereoselectivity under varying conditions (chlorenium ion donor, solvent polarity, concentration).

Main Results:

• Variable reaction orders were observed for syn and anti alkene addition processes.
• Mechanistic analysis suggests concerted AdE3-type pathways for both syn and anti additions.
• Factors influencing the preference for syn versus anti addition were identified.

Conclusions:

• The study provides a detailed mechanistic understanding of uncatalyzed chlorolactonization.
• Concerted AdE3 pathways are proposed for both syn and anti additions.
• The findings serve as reference points for future research on stereoselective halofunctionalization reactions.