Pyrrolidine-oxadiazolone conjugate as new organocatalyst for asymmetric aldol condensation

Abstract

A proline-based, chiral bi-functional organocatalyst containing both pyrrolidine and oxadiazolone heterocycle, has been successfully applied for stereoselective aldol reactions. The replacement of polar -COOH group of proline with bioisostere oxadiazolone ring provides excellent solubility of this catalyst in various organic solvents compared to low soluble proline. As a result, the organocatalyst effectively catalyzed the asymmetric condensation reaction between differently substituted aromatic aldehydes and various symmetrical and unsymmetrical ketones to produce the corresponding aldol products with excellent stereoselectivities (dr: 97:3, ee >99.9%) at room temperature in open-air.

GRAPHICAL ABSTRACT

Keywords:

• Pyrrolidine-oxadiazolone conjugate
• organocatalysis
• stereoselective aldol reaction
• high enantioselectivity
• room temperature reaction

Acknowledgements

C.K.M. is gratefully acknowledged TCGLS and CU for giving the opportunity to pursue this research work and also obliged to the analytical team at TCGLS for structural elucidation. S.M. thanks UGC, New Delhi, India, for offering Senior Research Fellowship (SRF). C.K.M. and M.K. gratefully recognize the research collaboration with CU.

Disclosure statement

No potential conflict of interest was reported by the author(s).