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Hydroboration Catalyzed by 1,2,4,3-Triazaphospholenes
Chieh-Hung Tien1, Matt R Adams1, Michael J Ferguson2
1Department of Chemistry, Dalhousie University , 6274 Coburg Road, P.O. Box 15000, Halifax, Nova Scotia, Canada B3H 4R2.
Organic Letters
|October 11, 2017
Summary
New 1,2,4,3-triazaphospholenes (TAPs) catalyze hydroboration reactions. These novel catalysts are more modular and effective than previous systems, enabling new synthetic pathways.
Area of Science:
- Organometallic Chemistry
- Catalysis
- Organic Synthesis
Background:
- Diazaphospholenes have been explored as catalysts for hydroboration.
- A need exists for more modular and versatile catalytic scaffolds in organic synthesis.
Purpose of the Study:
- To synthesize and investigate the catalytic activity of novel 1,2,4,3-triazaphospholenes (TAPs).
- To compare the catalytic efficiency of TAPs with existing diazaphospholene systems.
- To elucidate the catalytic mechanism of TAP-mediated hydroborations.
Main Methods:
- Synthesis of 1,2,4,3-triazaphospholene (TAP) halides.
- Catalytic testing of TAP halides in the hydroboration of imines and α,β unsaturated aldehydes using pinacolborane.
- Density Functional Theory (DFT) calculations to investigate the reaction mechanism.
Main Results:
- Successful synthesis and characterization of TAPs.
- TAP halides demonstrated catalytic activity in the 1,2 hydroboration of 19 imines and three α,β unsaturated aldehydes.
- TAPs enabled hydroboration of substrates that were unreactive with previous diazaphospholene catalysts.
- DFT calculations suggest a distinct catalytic mechanism involving a triazaphospholene cation.
Conclusions:
- 1,2,4,3-triazaphospholenes (TAPs) represent a promising new class of catalysts for hydroboration.
- TAPs offer enhanced modularity and broader substrate scope compared to diazaphospholenes.
- The distinct catalytic mechanism of TAPs opens new avenues for catalyst design and application.