Mimicking enzymatic cation-π interactions in hydrazide catalyst design: access to trans-decalin frameworks

Area of Science:

• Organic Chemistry
• Catalysis
• Stereoselective Synthesis

Background:

• Chiral bicyclic hydrazide organocatalysts show limitations in catalyzing (E)-polyene cyclization.
• Previous catalysts exhibit poor selectivity for (E)-polyenes compared to (Z)-polyenes.

Purpose of the Study:

• To develop novel organocatalysts for efficient (E)-polyene bicyclization.
• To achieve high enantioselectivity and diastereoselectivity in the formation of trans-decalin structures.

Main Methods:

• Synthesis of diazapane carboxylates bearing terphenyl groups as novel organocatalysts.
• Investigation of catalytic activity in the bicyclization of (E)-polyene substrates.
• Analysis of enantioselectivity and diastereoselectivity using chiral analysis techniques.

Main Results:

• Diazapane carboxylates efficiently catalyze (E)-polyene bicyclization.
• Achieved up to 94:6 er (enantiomeric ratio) and high diastereoselectivity for trans-decalin formation.
• Catalyst mechanism involves simultaneous iminium ion initiation and cation-π stabilization of intermediates.

Conclusions:

• Terphenyl-substituted diazapane carboxylates are effective catalysts for (E)-polyene bicyclization.
• The developed catalysts overcome previous selectivity limitations for (E)-polyenes.
• The dual mode of action (iminium ion formation and cation-π interactions) is key to catalytic efficiency and selectivity.