3-Vinyl-2,6-dioxacyclohexan-1-ones 1, by treatment with N-tosyl or N-aryl isocyanates and a catalytic amount of Pd0, are converted into N-tosyl- and N-aryl-3-vinyl-2-aza-6-oxacyclohexan-1-ones 2 in good yields and with unique stereoselectivity.
Regio- and Stereoselective Synthesis of 1,3-Hydroxyl Amines via Palladium-Catalyzed Carbonate-Carbamate Transformation with Unique Stereoselectivity: Synthesis of 3-Amino-4-penten-1-ols
The transformation of cyclic carbonates 1 to cyclic carbamates 4 is achieved in the presence of aryl or sulfonyl isocyanate by the catalysis of Pd(0) in high yield and with high structural flexibility. The reaction shows unique stereoselectivity: 3,4-disubstituted carbonates 2, irrespective of the composition of their stereoisomers, provide trans-5 exclusively or predominantly over cis-5. Mixtures of cis- and trans-3,5-disubstituted carbonates 3 furnish either cis-6 or trans-6 in high selectivity depending on the reaction conditions (kinetic or thermodynamic control, respectively). H-1 NMR and X-ray structure analyses of 5 and 6 indicate that the stereochemical outcome is governed by an A1,2-strain between N-sulfonyl and C5-vinyl substituents.
Palladium-Catalyzed Asymmetric Decarboxylative [4+2] Dipolar Cycloaddition of 4-Vinyl-1,3-dioxan-2-ones with α,β-Disubstituted Nitroalkenes Enabled by a Benzylic Substituted P,N-Ligand
The Pd-catalyzed asymmetric [4+2] cycloaddition reaction of an aliphatic 1,4-dipole with singly activated electron-deficient alkenes is realized for the first time, enabled by using a newly developed benzylic substituted P,N-ligand, affording tetrahydropyrans having three continuous chiral centers in high yields with high diastereo- and enantioselectivities. The rational transition states of the reaction as well as the role of the benzylic chiral center are proposed.
Synthesis of 2-vinyl-γ-butyrolactones by the palladium-catalyzed decarboxylative carbonylation of 3-vinyl-1-oxo-2,6-dioxacyclohexanes
作者:Yoshinao Tamaru、Takashi Bando、Makoto Hojo、Zen-ichi Yoshida