Reactivity of B‐Xanthyl N‐Heterocyclic Carbene‐Boranes
Résumé
The synthesis and reactivity of mono and bis-S-xanthyl NHC-boranes is reported. The new NHC-boranes are prepared via nucleophilic exchange at boron from either mono or bis-triflyl NHC–boranes, themselves obtained by protolysis of the NHC–BH3 starting compounds. The B–H bond of the S-xanthyl NHCboranes can be cleaved both homolytically and heterolytically, albeit the latter is more synthetically useful. The S-xanthyl NHC-boranes can reduce both aldehydes and imines. The B–S bond can also be cleaved homolytically. Under UV irradiation, the S-xanthyl NHC-boranes generate NHC–boryl radicals that can initiate radical polymerizations of acrylates.
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