A series of alkyl-substituted ketones are shown to activate hydrogen in the presence of B(C6F5)3, affording the corresponding borinic esters RR'CHOB(C6F5)2. The mechanism is shown to proceed via H2 activation, hydride delivery and protonation of a C6F5 group. The aliphatic aldehyde Et2CHCHO reacts with B(C6F5)3 or BPh3 to give boron enolates Et2C[double bond, length as m-dash]CH(OBAr2) (Ar = C6F5, Ph). These latter species are amenable to FLP-catalyzed reduction to the corresponding borinic esters.
Diphenyldiazomethane reacts with HB(C 6 F 5 ) 2 and B(C 6 F 5 ) 3 ,r esulting in 1,1-hydroboration and adduct formation, respectively.The hydroboration proceeds via aconcerted reaction involving initial formation of the Lewis adduct Ph 2 CN 2 BH(C 6 F 5 ) 2 .T he highly sensitive adduct Ph 2 CN 2 (B-(C 6 F 5 ) 3 )l iberates N 2 and generates Ph 2 CB(C 6 F 5 ) 3 .D FT computations reveal that formation of Ph 2 CN 2 B(C 6 F 5 ) 3 from carbene,N 2 ,a nd borane is thermodynamically favourable, suggesting steric frustration could preclude carbene-borane adduct formation and affect FLP-N 2 capture. Scheme 1. Metal-N 2 -borane and diazomethane-borane reactions.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.
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