N-Triflylphosphoramides: highly acidic catalysts for asymmetric transformations

Area of Science:

• Organic Chemistry
• Catalysis
• Asymmetric Synthesis

Background:

• N-Triflylphosphoramides (NTPA) are increasingly utilized as catalysts in asymmetric synthesis.
• NTPA function as strong Brønsted acids, surpassing conventional phosphoric acids (PA) in catalytic activity.
• Their acidic and asymmetric active sites facilitate the activation of challenging, unreactive substrates.

Purpose of the Study:

• To review asymmetric transformations catalyzed by N-Triflylphosphoramides (NTPA) reported in the last ten years.
• To classify these reactions based on the enantioselective step.
• To highlight the application of NTPA in total synthesis and provide mnemonics for understanding enantioselectivity.

Main Methods:

• Literature review of asymmetric transformations employing NTPA catalysts over the past decade.
• Classification of reactions based on the key enantioselective step.
• Categorization into eight reaction types: cycloadditions, electrocyclisations, polyene cyclisations, additions to imines and carbocations, aldol reactions, additions to double bonds, rearrangements, and desymmetrisations.

Main Results:

• A comprehensive compendium of NTPA-catalyzed asymmetric reactions is presented.
• Reactions are systematically organized into defined categories based on their stereochemistry-determining step.
• The utility of NTPA in complex molecule synthesis (total synthesis) is demonstrated.

Conclusions:

• N-Triflylphosphoramides (NTPA) represent a powerful class of catalysts for diverse enantioselective reactions.
• The classification scheme provides a structured understanding of NTPA-catalyzed transformations.
• Further development and application of NTPA in organic synthesis are anticipated.