Rh(I)-Catalyzed CO Gas-Free Carbonylative Cyclization Reactions of Alkynes with 2-Bromophenylboronic Acids Using Formaldehyde
journal contributionposted on 16.04.2009, 00:00 by Tsumoru Morimoto, Kae Yamasaki, Akihisa Hirano, Ken Tsutsumi, Natsuko Kagawa, Kiyomi Kakiuchi, Yasuyuki Harada, Yoshiya Fukumoto, Naoto Chatani, Takanori Nishioka
The rhodium(I)-catalyzed reaction of alkynes with 2-bromophenylboronic acids in the presence of paraformaldehyde resulted in a CO gas-free carbonylative cyclization, yielding indenone derivatives. [RhCl(BINAP)]2 and [RhCl(cod)]2 were responsible for the decarbonylation of formaldehyde and the subsequent carbonylation of alkynes with 2-haloboronic acids, respectively, leading to efficient whole carbonylation. Sterically bulky and electron-withdrawing groups on unsymmetrically substituted alkynes favored the α-position of indenones.