title: Pd(OAc)2-catalyzed carbonylation of amines.
abstract: A phosphine-free catalytic system [Pd(OAc)2-Cu(OAc)2-air] induced a substrate-specific carbonylation of amines in boiling toluene under CO gas (1 atm). Symmetrical N,N'-dialkylureas were obtained by the carbonylation of primary amines. N,N,N'-Trialkylureas were selectively formed by addition of a secondary amine to the above reaction vessel. Secondary amines did not give tetraalkylureas. However, dialkylamines with a phenyl group on their alkyl chains, such as N-monoalkylated benzylic amine or phenethylamine derivatives, underwent a direct aromatic carbonylation to afford five- or six-membered benzolactams. In the carbonylation, the chelation effect or steric repulsion between Pd(II) and the meta-substituent in the ortho-palladation and the ring sizes of cyclopalladation products that were formed prior to carbonylation were found to generate good site selectivity and increase the reaction rate. In contrast, carbonylation of omega-arylalkylamines with a hydroxyl group gave neither ureas nor benzolactams but instead produced 1,3-oxazolidinones smoothly. Hydrochlorides of amines also underwent carbonylation to afford the corresponding amides under the conditions used. This procedure made it possible to prepare ureas of amino acid esters and N-alkylcarbamates in practical yields.
authors.affiliation: Laboratory of Organic Synthesis, Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan. orito@org-mc.eng.hokudai.ac.jp
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Orito
authors.forename: Mamoru
authors.initials: M
authors.lastname: Miyazawa
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Nakamura
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Horibata
authors.forename: Harumi
authors.initials: H
authors.lastname: Ushito
authors.forename: Hideo
authors.initials: H
authors.lastname: Nagasaki
authors.forename: Motoki
authors.initials: M
authors.lastname: Yuguchi
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamashita
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Masao
authors.initials: M
authors.lastname: Tokuda