Suzuki-Miyaura Cross-Coupling Of 3,4-Disubstituted 5-Bromoisoxazoles: An Efficient Access To Trisubstituted Isoxazoles

The Suzuki-Miyaura cross-coupling of 3,4-disubstituted 5-bromoisoxazoles 1 at the C5 position has successfully proceeded in the presence of Pd-2(dba)(3) and P(t-Bu)(3)center dot HBF4 catalysts to give the corresponding trisubstituted isoxazoles 3 in good to high yields while suppressing the formation of ketone 4 as a byproduct. The use of bulky phosphine ligand P(t-Bu)(3)center dot HBF4 is essential for the current transformation, and the formation of ketone 4, which was a major product in the previous report, was able to be suppressed under the current conditions. (C) 2021 Elsevier Ltd. All rights reserved.