N-heterocyclic carbene-mediated transformations of silicon reagents

An N-heterocyclic carbene-catalyzed switchable reaction of 9-(trimethylsilyl)fluorene and aldehydes: chemoselective synthesis of dibenzofulvenes and fluorenyl alcohols

An N-heterocyclic carbene-catalyzed synthesis of dibenzofulvenes and fluorenyl alcohols was developed. In the presence of 10 mol% NHC (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and 4 Å molecular sieves, 9-(trimethylsilyl)fluorene undergoes an olefination reaction with aldehydes to produce dibenzofulvenes in 43-99% yields. However, on reducing the NHC loading to 1 mol% and with the addition of water, 9-(trimethylsilyl)fluorene selectively undergoes nucleophilic addition with aldehydes to afford fluorenyl alcohols in 40-95% yields.

Stereoselective synthesis of α-fluoroacrylonitriles via organocatalytic cyanation of gem-difluoroalkenes and TMSCN

DBU-catalyzed cyanation of gem-difluoroalkenes with TMSCN, a highly stereoselective synthesis of α-fluoroacrylonitriles.

N-heterocyclic carbene-catalysed pentafluorophenylation of aldehydes

N-heterocyclic carbenes have been utilized as highly efficient organocatalysts to catalyse multifluorophenylation of aldehydes with fluorinated aryltrimethylsilanes to afford the corresponding adducts in 49–99% yields.

Organocatalytic direct difluoromethylation of aldehydes and ketones with TMSCF2H

Organocatalytic direct difluoromethylation of aldehydes and ketones with TMSCF₂H.