Selective oxidative carbonylation of amines to oxamides and ureas catalyzed by palladium complexes

Kozo Hiwatari, Yoshihito Kayaki, Koshi Okita, Tomohiro Ukai, Isao Shimizu, Akio Yamamoto

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38 Citations (Scopus)

Abstract

A new process for converting secondary amines into N,N,N′,N′- tetraalkyloxamides under CO pressure, catalyzed by homogeneous palladium complexes in the presence of 1,4-dichloro-2-butene (DCB) as an oxidant, has been developed. The mechanism of the oxidative double-carbonylation process, consisting of the oxidation of Pd(0) to Pd(11) with DCB through a β-chloride elimination of the η3-(chloromethyl) allylpalladiuni(11) intermediate, the formation of mono- and bis(carbamoyl)palladium species, and a reductive elimination of the two carbamoyl ligands, is proposed based on studies of the behavior of carbamoylpalladium complexes. When primary amines are employed with DCB as the oxidant, N,N′-dialkyloxamide is catalytically produced, whereas urea is exclusively produced when iodine is used as the oxidant. The reaction of an N-monopropylcarbamoylpalladium complex with propylamine under CO gave N,N′-dipropylurea, whereas a treatment with diethylamine yielded unsymmetrical N,N-diethyl-N′-propylurea, implying the intermediate formation of propyl isocyanate that is converted into the urea upon a reaction with the added amine. A kinetic study on the reaction of chloro-N- propylcarbamoylpalladium with triethylamine suggested a process proceeding through a base-promoted dcprolonalion of the N-monoalkylcarbamoyl ligand to form propyl isocyanate.

Original languageEnglish
Pages (from-to)2237-2250
Number of pages14
JournalBulletin of the Chemical Society of Japan
Volume77
Issue number12
DOIs
Publication statusPublished - 2004

ASJC Scopus subject areas

  • Chemistry(all)

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