How general is the imidazolidine fragmentation route to 2-azaallyl anions?

Not very general! Scheme 10 shows some imidazolidines that failed to undergo cycloreversion/cycloaddition. The first compound shows that an N-aryl substituent inhibits the reaction. The remaining compounds show that, regardless of the N-substituent, no cycloreversion is observed where the 2-azaallyl anion would be unstabilized (i.e., by a C-aryl substituent). Our tin-lithium exchange methodology is the only method available for the generation of such unstabilized anions [4].


The cycloreversion of N-lithioimidazolidines to 2-azaallyl anions has been demonstrated. This method is restricted to the formation of anions that bear at least one aryl group. An unusual stereochemical complementarity between the imidazolidine and deprotonation routes to 2-azaallyl anions was observed. Suggestions on the last point are particularly welcome.


We thank the National Institutes of Health forfunding this work.

1. Introduction
2. Observations of Imidazolidine Intermediates in the Deprotonation Route to 2-Azaallyl Anions
3. Deliberate Generation of Imidazolidines from 2-Azaallyl Anions, and Their Use as 2-Azaallyl Anion Precursors
4. Synthesis of Imidazolidines from Diamines, and Their Use in 2-Azaallyl Anion Generation
5. An Unusual Stereochemical Complementarity
6. How General is the Imidazolidine Fragmentation Route to 2-Azaallyl Anions? and Conclusion (This page)
7. Experimental Section
8. References