(2-Fluoroallyl)boration of Ketones with (2-Fluoroallyl)boronates

Abstract

Efficient routes toward activation of gem-chlorofluorocyclopropane-derived (2-fluoroallyl)boronates for allylboration of various ketones including functionalized and low-reactive ones were developed. Increasing the boron electrophilicity by the transformation of a boronate moiety into a borinic ester with n BuLi/trifluoroacetic anhydride (TFAA) makes (2-fluoroallyl)boration of acetyl arenes/hetarenes and aliphatic ketones possible with high diastereoselectivity. For low-reactive or sterically hindered ketones (e.g., benzophenone, adamantanone), "CuF"based catalysts were developed: (NHC)CuF•HF and (NHC)-CuOTf in the presence of an excess of KHF 2 (NHC = IPr, SIPr, IPr Cl ).

Amine adducts of triallylborane as highly reactive allylborating agents for Cu(i)-catalyzed allylation of chiral sulfinylimines

“…In fact, all of those reactions in which the rate of allylic transfer is sluggish would be rapidly carried out in the presence of amine adducts. 67–102…”

“…101 (2-Fluoroallyl) boronates were studied in the NHC-Cu(I)-catalyzed allylation of ketones by Novikov. 102 To finalize this brief overview, we can conclude that a great deal of catalytic allylation work has been done on low active and stable allylboronates. Moreover, a combination of this vast toolkit of boronate-based allylation methods with catalytic synthesis of allylborates makes this methodology one of the most significant vectors of boronate chemistry.…”

“…Along with phosphine complexes, a number of NHC-Cucomplexes have been used for the allylation. [97][98][99][100][101][102] Therefore, a simple NHC-CuCl-complex [Cu-4] was tested in the reaction. As expected, the determined rate constant was almost 6 times lower with respect to the phosphine complex [Cu-1].…”

“…101 (2-Fluoroallyl)boronates were studied in the NHC-Cu( i )-catalyzed allylation of ketones by Novikov. 102…”