Novel resin supported gold catalysts were developed for the synthesis of carbamates by oxidative carbonylation of aniline and its derivatives. At 175 ℃ and 5.0 MPa, the oxidative carbonylation of aniline to the corresponding carbamates over these catalysts could be proceeded with a high conversion(96%), selectivity(99%) and 532 for TOF was achieved. The resin supported gold castalyst would be reusable and the catalytic performance was much better than that of the resin supported Pd catalyst.
The synthesis of dialkylureas from amines by oxidative carbonylation with sulfuric acid modified zirconia supported palladium catalyst was investigated under relatively mild reaction conditions. High conversions and yields for the synthesis of symmetric dialkylureas from the reaction between same aliphatic amines were achieved. This supported catalyst can also be easily separated and recovered from the solvent after the reaction.
At 200 ℃ and 50 mPa, the oxidative carbonylation of amines catalyzed by organic gold complexes HAuCl 4, Au(PPh 3)Cl, Au(PPh 3) 2Cl, Au(PPh 3)NO 3 and [Au(PPh 3)] 2S afforded R(NHCO 2CH 3) n with a high conversion and selectivity. The best results were obtained when using the catalyst Au(PPh 3)Cl in the presence of PPh 3. The catalytic efficiency of catalytic Au(PPh 3)Cl was compared to Pd(PPh 3) 2Cl 2, e.g. the conversion was 97.2% and selectivity was 89% when using catalyst Au(PPh 3)Cl in the presence of PPh 3, while the conversion was 98.8% and selectivity was 86% when using catalyst Pd(PPh 3) 2Cl 2 in the presence of PPh 3. The experimental results suggested that Au complexes might be promising catalysts instead of Pd catalysts for the oxidative carbonylation of amines to carbamates.
A novel synthesis of several isocyanates by direct electrocatalytical carbonylation of corresponding amines can proceed through an electrochemically regenerable palladium(Ⅱ) catalyst in combination with copper acetate as cocatalyst with an excellent conversion and selectivity under mild conditions. The results show that Pd(PPh 3) 2Cl 2 was the best catalyst. For aromatic amines, the main products were the corresponding isocyanates. And for aliphatic amines, various products were detected.
Novel combined PdCl 2(RuCl 3) with ZrO 2 SO 3 catalysts were developed for the synthesis of carbamates by oxidative carbonylation of aliphatic and aromatic amines. At 170 ℃ and 4.0 MPa, oxidative carbonylation of aromatic amines to the corresponding carbamates over this catalyst system could be proceeded with a high conversion and selectivity. Especially when β naphthylamine was used as the substrate, 100% conversion and 95% selectivity were obtained in only 15 min. The catalytic performance of PdCl 2/ZrO 2 SO 3 was better than that of RuCl 3/ZrO 2 SO 3 for such oxidative carbonylation reaction. Possible role of ZrO 2 SO 3 as co catalyst was also conjectured.
