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A redox-active diborane platform performs C(sp 3 )-H activation and nucleophilic substitution reactions.
- Source :
-
Chemical science [Chem Sci] 2018 Mar 19; Vol. 9 (15), pp. 3881-3891. Date of Electronic Publication: 2018 Mar 19 (Print Publication: 2018). - Publication Year :
- 2018
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Abstract
- Organoboranes are among the most versatile and widely used reagents in synthetic chemistry. A significant further expansion of their application spectrum would be achievable if boron-containing reactive intermediates capable of inserting into C-H bonds or performing nucleophilic substitution reactions were readily available. However, current progress in the field is still hampered by a lack of universal design concepts and mechanistic understanding. Herein we report that the doubly arylene-bridged diborane(6) 1 H <subscript>2</subscript> and its B[double bond, length as m-dash]B-bonded formal deprotonation product Li <subscript>2</subscript> [ 1 ] can activate the particularly inert C(sp <superscript>3</superscript> )-H bonds of added H <subscript>3</subscript> CLi and H <subscript>3</subscript> CCl, respectively. The first case involves the attack of [H <subscript>3</subscript> C] <superscript>-</superscript> on a Lewis-acidic boron center, whereas the second case follows a polarity-inverted pathway with nucleophilic attack of the B[double bond, length as m-dash]B double bond on H <subscript>3</subscript> CCl. Mechanistic details were elucidated by means of deuterium-labeled reagents, a radical clock, α,ω-dihaloalkane substrates, the experimental identification of key intermediates, and quantum-chemical calculations. It turned out that both systems, H <subscript>3</subscript> CLi/ 1 H <subscript>2</subscript> and H <subscript>3</subscript> CCl/Li <subscript>2</subscript> [ 1 ], ultimately funnel into the same reaction pathway, which likely proceeds past a borylene-type intermediate and requires the cooperative interaction of both boron atoms.<br /> (This journal is © The Royal Society of Chemistry 2018.)
Details
- Language :
- English
- ISSN :
- 2041-6520
- Volume :
- 9
- Issue :
- 15
- Database :
- MEDLINE
- Journal :
- Chemical science
- Publication Type :
- Academic Journal
- Accession number :
- 29780520
- Full Text :
- https://doi.org/10.1039/c8sc00743h