Palladium-catalyzed asymmetric arylation, vinylation, and allenylation of tert-cyclobutanols via enantioselective C-C bond cleavage.
A novel enantioselective C-C bond cleavage has been achieved using palladium catalysts and chiral N,P-bidentate ligands in the asymmetric arylation, vinylation, and allenylation of tert-cyclobutanols. In these reactions, the enantioselective beta-carbon elimination of Pd(II) alcoholate formed in situ is the key step. Treatment of tert-cyclobutanols with arylating reagents in toluene in the presence of Pd(OAc)(2), a chiral ferrocene-containing N,P-bidentate ligand, and Cs(2)CO(3) affords optically active gamma-arylated ketones in excellent yields with high enantioselectivity (up to 95% ee). When vinylating reagents are used in place of arylating ones, the asymmetric vinylation also proceeds to afford optically active gamma-vinylated ketones in high yields with good to high enantioselectivity. When propargylic acetates are used, which are known to generate (sigma-allenyl)palladium complexes with Pd(0) species, asymmetric allenylation occurs to afford optically active gamma-allenylated ketones in moderate to good yields with moderate to high enantioselectivity.
Matsumura
Satoshi
S
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
Maeda
Yasunari
Y
Nishimura
Takahiro
T
Uemura
Sakae
S