Palladium(II)-Catalyzed Intramolecular Aminocarbonylation of endo-Carbamates under Wacker-Type Conditions.
Pd(II)-catalyzed intramolecular aminocarbonylation of olefins bearing many types of nitrogen nucleophiles has been examined under two typical conditions: acidic conditions [conditions A, typically PdCl(2) (0.1 equiv) and CuCl(2) (3.0 equiv) under 1 atm of CO at room temperature in methanol] and buffered conditions [conditions B, typically PdCl(2) (0.1 equiv) and CuCl(2) (2.3 equiv) under 1 atm of CO at 30 degrees C in trimethyl orthoacetate]. Among nitrogen nucleophiles, endo-carbamates 7 display distinctive reactivity: endo-carbamates 7a-k smoothly undergo intramolecular aminocarbonylation under conditions B to furnish 4-[(methoxycarbonyl)methyl]-2-oxazolidinones 8a-k in good yields, while they would not undergo the expected reaction under conditions A. Other nitrogen nucleophiles (exo-ureas 1, endo-ureas 3, exo-carbamates 5, and exo-tosylamides 9), on the other hand, satisfactorily undergo aminocarbonylation only under conditions A to give rise to 2, 4, 6, and 10, respectively, in good yields. Under conditions B, they are unreactive and provide either the expected products in poor yields or intractable mixtures of products. On the basis of this contrasting reactivity between endo-carbamates and other nitrogen nucleophiles, the chemoselective aminocarbonylation of 7l-o has been achieved; aminocarbonylation takes place at the endo-carbamate moieties to furnish 8l-o exclusively under conditions B, and aminocarbonylation occurs at the exo-carbamate, exo-urea, and exo-tosylamide moieties to yield 13a-d exclusively under conditions A.
Harayama
Hiroto
H
Department of Applied Chemistry, Faculty of Engineering, Nagasaki University, 1-14 Bunnkyo, Nagasaki 852, Japan.
Abe
Atsuhiro
A
Sakado
Tomonori
T
Kimura
Masanari
M
Fugami
Keigo
K
Tanaka
Shuji
S
Tamaru
Yoshinao
Y