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Crystalline Monomeric Allenyl/Propargyl Radical
Max M Hansmann1, Mohand Melaimi1, Guy Bertrand1
1UCSD-CNRS Joint Research Laboratory (UMI 3555), Department of Chemistry and Biochemistry, University of California, San Diego , La Jolla, California 92093-0358, United States.
Journal of the American Chemical Society
|October 20, 2017
Summary
Cyclic (alkyl)(amino)carbenes (CAACs) reduction yields propargyl/allenyl radicals. These radicals exhibit diverse dimerization behaviors, with the first solid-state X-ray crystallography of an allenyl radical reported.
Area of Science:
- Organic Chemistry
- Carbene Chemistry
Background:
- Cyclic (alkyl)(amino)carbenes (CAACs) are versatile ligands and reagents in organic synthesis.
- Radical intermediates are crucial in many chemical transformations.
- The stability and reactivity of allenyl radicals are not well understood.
Purpose of the Study:
- To investigate the generation and behavior of propargyl/allenyl radicals derived from CAACs.
- To explore the factors influencing the dimerization or monomeric state of these radicals.
- To characterize an allenyl radical using single crystal X-ray crystallography.
Main Methods:
- Reduction of alkynyl iminium salts generated from CAACs.
- Analysis of radical behavior in solution and solid states.
- Single crystal X-ray crystallography for structural determination.
Main Results:
- Propargyl/allenyl radicals were successfully generated.
- Radical dimerization was observed to be dependent on CAAC and alkyne substituents.
- Monomeric allenyl radicals were characterized in the solid state for the first time via X-ray crystallography.
Conclusions:
- The study demonstrates tunable radical behavior based on CAAC and alkyne structure.
- The first crystallographic evidence of a stable allenyl radical was obtained.
- This work provides new insights into the chemistry of persistent organic radicals.
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