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 α,ω-amino alcohols [3-aminopropanol (3-AP), 4-aminobutanol (4-AB), 5-aminopentanol (5-APe), 6-aminohexanol (6-AH)] with CO/O2 mixtures (O2 = 5 mol%) in the presence of Pd(II)/ligand/NEt3·HI catalytic systems. The catalytic process takes place under very mild conditions (p(CO/O2) = 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.

Graphical abstractUnder very mild conditions (303–333 K; p(CO/O2) = 0.1 MPa; O2 = 5 mol%), LnPdCl2/NEt3·HI systems [(L = 2,2′-dipyridine (dipy) (n = 1); 2-(β-diphenylphosphine)ethylpyridine) (PN) (n = 1); PPh3 (n = 2); CH3CN (n = 2)] effectively promote the oxidative carbonylation of α,ω-amino alcohols to symmetrical N,N′-bis(hydroxyalkyl)ureas with high yield and selectivity.Figure optionsDownload full-size imageDownload high-quality image (71 K)Download as PowerPoint slide