Group 10 metal-promoted oxidations catalytic oxidative carbonylation

Group 10 metal-promoted oxidations catalytic oxidative carbonylation 

Caution Employ the standard precautions outlined in the introduction of this chapter for this reaction. Carbon monoxide is odourless and highly toxic even at low concentration it must only be used in an efficient fume hood. 

Clean all glassware sequentially in soap solution, water, and acetone. Allow the acetone to evaporate and then dry the apparatus in an electric oven (105 O for at least 1 h. 

1 mL of water, a magnetic stirrer bar, palladium(ll) chloride (0.14 g, 0.78 mmol), copper(ll) chloride (0.20 g, 1.50 mmol), and 1 mL of concentrated hydrochloric acid into the flask by temporarily removing the T 19/22 cone adapter. 

Stir the mixture and adjust the carbon monoxide gas regulator so that the exit bubbler shows a flow of about two bubbles per second. Start the oxygen flow and adjust its rate until it is about half that of the carbon monoxide. The combined gas flow as measured by the exit bubbler should be about 2-3 bubbles per second. The flow rate of the carbon monoxide must be significantly greater than that of the oxygen or the regioselectivity of the reaction suffers. 

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The oxidative carbonylation of amines to give ureas is at present one of the most attractive ways for synthesizing this very important class of carbonyl compounds via a phosgene-free approach. Ureas find extensive application as agrochemicals, dyes, antioxidants, resin precursors, synthetic intermediates (also for the production of carbamates and isocyanates), and HIV-inhibitors. Many transition metals (incuding Au [244], Co [248,253-255], Cu [242], Mn [249,256-258], Ni [259], Rh [246,247,260-262], Ru [224,260,263] and especially Pd [219,225,226,264-276], and, more recently, W [277-283]) as well as main-group elements (such as sulfur [284-286] and selenium [287— 292]) have been reported to promote the oxidative carbonylation of amines, usually under catalytic conditions. In some cases, carbamates and/or oxamides are formed as byproducts, thus lowering the selectivity of the process. 

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