Rhodium-catalyzed asymmetric 1,4-additions of electron-deficient
heteroaryl groups to α,β-unsaturated carbonyl
compounds were established. The reaction resulted in very low yields due
to competitive C-B bond cleavage when arylboronic acids, their
pinacol esters, or potassium trifluoroborates were used. However,
the corresponding lithium heteroaryl(triol)borates afforded 1,4-adducts
with high enantioselectivities up to 97% in the presence of
a rhodium(I) catalyst chelated with a chiral BINAP or BIPAM ligand.
heteroaryl cyclic triolborate - rhodium catalyst - asymmetric reaction - conjugate
addition
