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Versatile chemistry of six-membered NHC with boranes: bromination at sp3 borane, activation of the B–H bond of HBpin, and ring expansion of NHC.
- Source :
-
Dalton Transactions: An International Journal of Inorganic Chemistry . 10/14/2022, Vol. 51 Issue 38, p14452-14457. 6p. - Publication Year :
- 2022
-
Abstract
- The NHC·borane chemistry has been majorly restricted to imidazol-2-ylidene classes of carbenes. In our previous communication, we reported the synthesis of 6-SIDipp·BH3 [6-SIDipp = 1,3-di(2,6-diisopropylphenyl) tetrahydropyrimidine-2-ylidene] and its electrophilic substitution reaction with iodine. Here, we have shown selective bromination of a 6-SIDipp stabilized sp3 B–H bond. Treatment of 1.2 equivalents of N-bromosuccinamide with 6-SIDipp·BH3 gives a mixture of mono- and disubstituted products 6-SIDipp·BH2Br (1) and 6-SIDipp·BHBr2 (2). However, the reactions with alkyl bromides or carbon tetrabromide resulted in 6-SIDipp·BH2Br (1) selectively. Exploration of the chemistry of 6-SIDipp with BHCl2 and 9-BBN (9-borabicyclo[3.3.1]nonane) led to mono-6-SIDipp adducts 3 and 6a. Furthermore, 6a undergoes ring expansion to afford a seven-membered product, 6b, under mild conditions. Unlike BHCl2 or 9-BBN, the B–H bond of HBpin undergoes oxidative addition upon reaction with 6-SIDipp, epitomizing the first example (7) of a B–H bond insertion at NHCs. The analogous reactivity with HBcat led to a tetrahydropyrimidinium salt with B(cat)2 as a counteranion (8). [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 14779226
- Volume :
- 51
- Issue :
- 38
- Database :
- Academic Search Index
- Journal :
- Dalton Transactions: An International Journal of Inorganic Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 159501790
- Full Text :
- https://doi.org/10.1039/d2dt01707e