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Borylative cyclisation of diynes using BCl3 and borocations
Andrew J Warner1, Kieron M Enright, John M Cole
1School of Chemistry, University of Manchester, Manchester, M13 9PL, UK.
Organic & Biomolecular Chemistry
|May 24, 2019
Summary
Borylative cyclisation of 1,2-dialkynyl benzenes with boron trichloride (BCl3) can yield dibenzopentalenes or benzofulvenes. Borocations enhance selectivity for dibenzopentalene formation in this organic synthesis reaction.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
Background:
- 1,2-dialkynyl benzenes are versatile precursors in organic synthesis.
- Borylative cyclisation offers a pathway to complex polycyclic aromatic hydrocarbons.
Purpose of the Study:
- To investigate the outcome of borylative cyclisation of 1,2-dialkynyl benzenes using BCl3.
- To explore the influence of substituents and boron reagents on reaction selectivity.
Main Methods:
- Reaction of 1,2-dialkynyl benzenes with BCl3.
- Analysis of product distribution based on substrate substituents.
- Use of borocations as an alternative boron source.
Main Results:
- The reaction yields dibenzopentalenes or benzofulvenes, depending on substituents.
- Stabilized vinyl cation intermediates favor benzofulvene formation.
- Borocations promote selective dibenzopentalene formation.
- Other diyne frameworks undergo selective intramolecular SEAr.
Conclusions:
- Substituent effects and the choice of boron reagent critically control the products of borylative cyclisation.
- This study provides insights into the mechanism and synthetic utility of borylative cyclisation reactions.
