Secondary amines can be catalytically carbonylated to symmetrical tetrasubstituted ureas using W(CO)6as the catalyst, I2as the oxidant, and CO as the carbonyl source. Preparation of the corresponding tetrasubstituted ureas from the aliphatic secondary amines HNR2(R = C2H5, n-Bu, i-Pr, PhCH2) and HNRR' (R,R' = -(CH2)4-; -(CH2)5-; PhCH2, CH3) was achieved in moderate yields. Aromatic secondary amines are unreactive. (C) 2000 Elsevier Science B.V.
McCusker, J. E., Qian, F., & McElwee-White, L. (2000). Catalytic oxidative carbonylation of aliphatic secondary amines to tetrasubstituted ureas. Journal of Molecular Catalysis A: Chemical, 159(1), 11–17. https://doi.org/10.1016/S1381-1169(00)00164-3