Oxalate formation, double carbonylation

Under appropriate conditions, alcohols and amines can undergo an oxidative double carbonylation process, with formation of oxalate esters (Eq. 34), oxamate esters (Eq. 35) or oxamides (Eq. 36). These reactions are usually catalyzed by Pd(II) species and take place trough the intermediate formation of bis(alkoxycarbonyl)palladium, (alkoxycarbonyl)(carbamoyl)palladium or bis(carbamoyl)palladium complexes, as shown in Scheme 29 (NuH, Nu H = alcohol or amine) [227,231,267,293-300]. 

F. OXAMIDE, OXALATE, AND OXAMATE FORMATION FROM PALLADIUM-CATALYZED DOUBLE CARBONYLATION... 

Oxamides, dialkyl oxalate esters, and oxamic add esters can be prepared by Pd-catalyzed double carbonylation of secondary amines and alcohols via incorporation of two molecules of carbon monoxide into amines and/or alcohols. Pd-catalyzed double carbonylation reactions of amines in the absence or presence of alcohol were reported earlier to give ox-amides and oxamic acid ester.t i t Selective formation of oxamides has been achieved by double carbonylation of secondary amines in the presence of iodide ion and dioxygen catalyzed by Pd(OAc>2 (Eq. 

Moffatt oxidation has several problems associated with it. One is formation of the urea product 64, which can be very difficult to remove. Treatment with oxalic acid is the most common method employed for the removal of the last vestiges of the dicyclohexylurea byproduct. Oxidation of homoallylic alcohols is sometimes accompanied by isomerization of the double bond into conjugation with the carbonyl group. This can be minimized or prevented by addition of pyridinium trifluoroacetate. A threefold excess of DCC and an excess of DMSO are usually required for Moffatt oxidation and these must be removed from the product. The... 

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