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Ti-catalyzed 1,2-Diamination of Alkynes Using 1,1-Disubstituted Hydrazines
Partha Sarathi Karmakar1, Yuya Kakiuchi2, Jaekwan Kim1
1Department of Chemistry, University of Minnesota-Twin Cities, Minneapolis, Minnesota 55455, United States.
A novel titanium catalyst enables both alkyne diamination and hydrohydrazination by altering reaction conditions. This discovery expands substrate scope for diamination and aids in designing new, selective titanium catalysts.
Area of Science:
- Organometallic Chemistry
- Catalysis
- Synthetic Organic Chemistry
Background:
- Alkyne diamination and hydrohydrazination are distinct titanium-catalyzed reactions.
- Historically, separate titanium catalysts were required for each reaction.
- Limited examples exist for alkyne diamination catalysis.
Purpose of the Study:
- To develop a single titanium catalyst capable of both alkyne diamination and hydrohydrazination.
- To understand how reaction conditions influence selectivity between these two transformations.
- To explore structure-activity relationships for designing improved catalysts.
Main Methods:
- Utilized a diamidoamine titanium catalyst, (NNN)Ti(═NNR2).
- Investigated selectivity control through changes in reaction conditions.
- Employed 15N NMR spectroscopy to analyze structure-activity relationships.
Main Results:
- Demonstrated that the diamidoamine titanium catalyst mediates both diamination and hydrohydrazination.
- Showed selectivity is governed by unimolecular (diamination) vs. bimolecular (hydrohydrazination) reaction pathways.
- Designed a novel, highly active diamination catalyst, (NNNSiMe2Ph)Ti(═NNR2) (1f), with bulkier ligands.
Conclusions:
- A single titanium catalyst can achieve both alkyne diamination and hydrohydrazination, controlled by reaction conditions.
- Understanding entropic differences at the selectivity branch point is key.
- The strategy can be extended to discover new titanium catalysts for alkyne diamination using 1,1-disubstituted hydrazines.
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