Carbonylation organic substrates

By definition, an oxidative carbonylation is a process in which carbon monoxide is inserted into an organic substrate under the action of a metal undergoing a reduction of its oxidation state [the reduction Pd(II) -> Pd(0)... 

A wide range of organic substrates can undergo an oxidative carbonylation reaction. Depending on reaction conditions, alkenes have been converted into -chloroalkanoyl chlorides (oxidative chloro-chlorocarbonylation) [1,2], succinic diesters (oxidative dialkoxycarbonylation) [3-20], a,/J-unsaturated esters [21,22] (oxidative monoalkoxycarbonylation), or /J-alkoxyalkanoic esters [11] (oxidative alkoxy-alkoxycarbonylation), according to Eqs. 10-13. 

Interest in the uses of HMPT has also been maintained, but a warning has been issued (by the E. I. du Pont de Nemours Company and the U.S. National Institute for Occupational Safety and Health) about its potential acute toxicity. HMPT has been used in the synthesis of 2,4-bis(dimethylamino)qui nolines,9 8 as a solvent for reactions between carbonyl compounds and sulphur," for the conversion of iV-benzylcarbox-amides into 3-phenylpropionitriles,100 in reactions between metals or organometallic compounds with a variety of organic substrates,101 and as a solvent for alkylation reactions of /J-keto-esters and related compounds in which the alkylation reaction is accompanied by de(alkoxycarbonylation) (Scheme 7).102... 

Incorporation of CO into an organic substrate usually occurs by insertion of CO into a C-metal bond. The requisite Cl-metal bond is formed by oxidative addition of a Pd(0) species into the Cl-Br bond, the normal first step upon combining a Pd(0) compound and an aryl halide. Coordination and insertion of CO follows. Addition of N to the carbonyl and loss of Pd(0) gives an iminium ion, which is trapped by EtOH to give the product. 

Tab. 15.1 Conversion of organic substrates to the respective carbonyl compounds when reacted with graphite oxide [77].

The anode is an ideal reagent to oxidize organic substrates such as oxygen-containing compounds (alcohols, carbonyl compounds, and carboxylic acids). Thereby these substrates can be converted avoiding chemical reagents, which simplifies the reaction conditions and the work-up. Additionally, the electron transfer leads selectively to a variety of reactive species, which can find further use in organic synthesis. 

Finally, polymer 594 has been used as an arene-catalyst to activate nickel from nickel(II) chloride and lithium, in order to perform hydrogenation of different organic substrates such as afkenes, afkynes, carbonyl compounds and their imines, alkyl and aryl halides (chlorides, bromides and iodides), aromatic and heteroaromatic compounds as well as nitrogen-containing systems such as hydrazines, azoxy compounds or Af-amino oxides, giving comparable results to those obtained in the corresponding reaction in solution . 

The oxidative properties of chromium-oxo complexes towards organic substrates have been thoroughly investigated, and several reviews have appeared in recent years.270 276 We will only briefly consider the oxidation of alcohols to carbonyl compounds, the epoxidation of alkenes and the hydroxylation of hydrocarbons. 

Metal-bound isocyanates give similar results to nitrosyl compounds.363,367 Starting with [Ru4(NCO)(CO)13] , one can obtain [Ru4(CO)i2N] in 78% yield upon thermolysis. Treatment of [Ru2(CO)r(NCO)] (x = 10,11) with Ru3(CO),2 leads to the hexanuclear nitride [Ru6(CO)i6N] in 82% yield. Organic nitroso and nitro can be similarly reduced by metal carbonyls or carbonylate anions. These reactions are discussed in the later section on reactions with organic substrates. 

Carbonylation of organic substrates was investigated using these well defined complexes. These carbonyl compounds exhibited catalytic properties in the carbonylation of organic substrates. In particular methanol carbonylation to methyl acetate in the gas phase was successfully attempted. Mechanistic and kinetic studies of this reaction over rhodium and iridium zeolites showed the similarities between the homogeneous and the zeolite mediated reactions. Aromatic ni-tro compounds were also converted to aromatic isocyanates using similar catalytic systems. The mechanistic aspect of this reaction will be also examined. 

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