Selective "one-pot" synthesis of functionalized cyclopentenones

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Organometallic Chemistry

Background:

• Squaric acid derivatives are versatile building blocks in organic synthesis.
• Developing efficient, one-pot synthetic methodologies is crucial for complex molecule preparation.

Purpose of the Study:

• To develop a novel one-pot method for synthesizing polyoxygenated cyclopentenones.
• To investigate the reaction mechanism, including intermediate formation and stereochemical outcomes.

Main Methods:

• One-pot double addition of vinyl magnesium bromide to squaric acid derivatives.
• Low-temperature protonation of reaction intermediates using trifluoroethanol (TFE).
• Density Functional Theory (DFT) calculations to study the cyclization step and diastereoselectivity.

Main Results:

• Successful preparation of polyoxygenated cyclopentenones (8) via a one-pot procedure.
• Identification of octatetraenes (6) as key reaction intermediates.
• Selective protonation of the octatetraene intermediate at low temperature (-78 °C).
• DFT studies confirmed the mechanism and explained the observed diastereoselectivity in the cyclization step.

Conclusions:

• The developed one-pot method offers an efficient route to polyoxygenated cyclopentenones.
• The reaction mechanism involves specific intermediate formation and stereoselective protonation.
• Computational studies provide valuable insights into the stereochemical control of the synthesis.