Abstract

Organocatalytic Michael addittion has been intensively studied in recent years and provides Michael adducts in a highly stereoselective way. We were interested in developing a simple and stereocontrolled route to 3,4-diphenyl substituted pyrrolidines, that are structural motifs found in many biologically active compounds, using a Michael reaction between nitrostyrenes and benzylic aldehydes as the key step. Extensive studies on the organocatalyzed Michael reaction between nitroalkenes and aliphatic aldehydes were conducted showing a high syn diastereselection according to Seebach’s model. However, only four examples using α-unsubstituted benzylic aldehydes have been reported and they showed a relative low syn diasteroselectivity. Since the higher acidity of the α protons of benzylic aldehydes relative to aliphatic ones could affect the reaction mechanism, we decided to examine and optimize the diastereochemical outcome of this process. Herein we report our results concerning diastereoselective Michael reaction between phenylacetaldehyde and nitrostyrene.

Highlights

  • Organocatalytic Michael addittion has been intensively studied in recent years and provides Michael adducts in a highly stereoselective way

  • The reaction yielded a clean product with high conversion and diastereselection. 1H NMR data of the major diastereomer obtained was in accordance with the already described for the syn adduct.[2]

  • The Michael adduct obtained can epimerize to the more stable anti product

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Summary

Introduction

Organocatalytic Michael addittion has been intensively studied in recent years and provides Michael adducts in a highly stereoselective way. A variety of solvents, secondary amines and catalyst concentrations were screened. The best result was obtained using toluene as solvent in presence of 20% mol of pyrrolidine and a 0.5 fold excess of aldehyde.

Results
Conclusion

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