Pd-catalysed oxidative carbonylation of amino alcohols to N,N′-bis(hydroxyalkyl)ureas under mild conditions using molecular oxygen as the oxidant

A very simple method has been developed for the selective synthesis of symmetrical N,N'-bis(hydroxyalkyl)ureas, OC[NH-(CH2)(x)-OH](2) (x = 3-6), by oxidative carbonylation of alpha,omega-amino alcohols [3-aminopropanol (3-AP), 4-aminobutanol (4-AB), 5-aminopentanol (5-APe), 6-aminohexanol (6-AH)] with CO/O-2 mixtures (O-2 = 5 mol%) in the presence of Pd(II)/ligand/NEt3 center dot HI catalytic systems. The catalytic process takes place under very mild conditions (p(CO/O-2) = 0-1 MPa; 303-333 K). The target products can be isolated in high yield through a very simple and straightforward procedure. The catalytic system can be easily recovered and recycled for several times. The influence of a few reaction parameters (nature of ancillary ligand and iodide co-catalyst, I/Pd molar ratio, etc.) on the catalytic activity has also been investigated and the main mechanistic features of the catalytic process fully elucidated. (C) 2010 Elsevier B.V. All rights reserved.