Carbonylation with CO

The reaction of organolithium reagents with CO is a fundamental reaction in organic chemistry and organometaUic chemistry. This reaction gives acyUithium 

In this reaction, carbonylation of di-lithio reagents 1 was assumed to give an acyclic carbonyUithium species 29 as the first reaction intermediate, which immediately tmdergoes cycloaddition reaction followed by sequential rearrangement to afford cyclic dianions, such as 31-A to 31-F (Fig. 4). We isolated and characterized the 

Since other intermediates 31A—F could be considered as resonance structures of OCp dianion 31-D, an equilibrium among these intermediates might exist. Specific substrates might differentiate the reaction site such as C or O and move the equilibrium, thus to afford different products. 

When 31 was treated with 2 equivalents of electrophiles such as Mel, Me2S04, allylic bromide, benzyl halides, or propargyl halides, 3-cyclopenten(Mie derivatives 

33 were resulted from reactions of 31 and two identical acid chlorides, while mixed double-acylated ones 34 were generated from one f-BuCOCl and one smaller acid chloride, respectively, in good to excellent isolated yields [31]. 

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Au Amines (oxidative carbonylation with CO/O2 to carbamates and symmetric ureas)... 

Another reaction of carbene la in an argon matrix is the carbonylation with CO to give ketene 10a.23 The carbonylation obviously proceeds with a very small barrier even at low temperature. The carboxylation with CO2, on the other hand, which is also a characteristic reaction of many carbenes, is not observed.70 The primary and rate-determining step of this reaction is the nucleophilic attack... 

The synthetic utility of the carbonylation of zirconacycles was further enhanced by the development of a pair of selective procedures producing either ketones or alcohols [30] and has been extensively applied to the synthesis of cyclic ketones and alcohols, most extensively by Negishi [22—27,29—33,65,87,131—134], as detailed below in Section I.4.3.3.4. The preparation of unsaturated aldehydes by carbonylation with CO is not very satisfactory. The use of isonitriles in place of CO, however, has provided a useful alternative [135], and this has been applied to the synthesis of curacin A [125]. Another interesting variation is the cyanation of alkenes [136]. Further developments and a critical comparison with carbonylation using CO will be necessary before the isonitrile reaction can become widely useful. The relevant results are shown in Scheme 1.35. 

In addition to this chapter, there are several books and reviews [1-8] which -inter alia- deal with carbonylations with CO andH20, two of them [9-10] specifically addressed to this topic. 

Carbonylation with CO in the presence of H2 leads to aldehydes. Bernhard Breit of Albert-Ludwigs-Universitat, Freiburg, has found (Chem. Comm. 2004, 114) that conversion of an allylic alcohol to the o-diphenylphosphanylbenzoate 8 allows highly diastereoselective and regioselective Rh-mediated one-carbon homologation. 

Arylthallium bis(trifluoroacetates) (see 2-22) can be carbonylated with CO, an alcohol, and a PdCl2 catalyst to give esters 387... 

Carbon Tetrachloride (telrachloromelhane). CAS 56-23-5. Carbon tetrachloride can be synthesized by the chlorination of CS . acetylene and other higher hydrocarbons but the primary source is the exhaustive chlorination of methane. It can be pyrolyzed to yield hexachloroethane. oxidized to phosgene and carbonylated with CO in the presence of AlClj to give trichloroaceiylchloride ... 

The reaction is only partially catalytic because nickel chloride is formed in side reactions. If a reducing agent such as iron powder is added to reduce nickel(II) dichloride to nickel carbonyl with CO, higher catalytic activity is observed (22). Some examples of the 2,5-hexadienoate ester synthesis are given in Table VI. 

Considering all possibilities, the protolytic cleavage of propane can be summarized according to Scheme 5.42. Since the butyryl cation was not detected, path a (involvement of n-propyl cation 34) can be excluded. Pathway b (protonation of the secondary C—H bond) is kinetically disfavored compared with protonation of the more electron-rich C—C bond (pathways c andrf). The large amount of methane leaves only path c as the major activation route of propane leading to the formation of ethylcarboxonium ion 112 (formation of the ethyl cation followed by carbonylation with CO). 

The acid-catalyzed hydrocarboxylation of alkenes (the Koch reaction) can be performed in a number of ways. In one method, the alkene is treated with carbon monoxide and water at 100-350°C and 500-1000-atm pressure with a mineral acid catalyst. However, the reaction can also be performed under milder conditions. If the alkene is first treated with CO and catalyst and then water added, the reaction can be accomplished at 0-50°C and 1-100 atm. If formic acid is used as the source of both the CO and the water, the reaction can be carried out at room temperature and atmospheric pressure.The formic acid procedure is called the Koch-Haaf reaction (the Koch-Haaf reaction can also be applied to alcohols, see 10-77). Nearly all alkenes can be hydrocarboxylated by one or more of these procedures. However, conjugated dienes are polymerized instead. Hydrocarboxylation can also be accomplished under mild conditions (160°C and 50 atm) by the use of nickel carbonyl as catalyst. Acid catalysts are used along with the nickel carbonyl, but basic catalysts can also be employed. Other metallic salts and complexes can be used, sometimes with variations in the reaction procedure, including palladium, platinum, and rhodium catalysts. The Ni(CO)4-catalyzed oxidative carbonylation with CO and water as a nucleophile is often called Reppe carbonylationP The toxic nature of nickel... 

Figure 6. Reversible formation and isomer transformations of Rh6(CO)i6 in NaY micropores after the cyclic procedures of oxidation, reduction and carbonylation with CO.

In this sense, the micropores alford preparative and catalytic advantages for encapsulated metal clusters over the conventional surface-grafted metal clusters. Regardless of the treatment and prevailing conditions that may involve several cyclic sequence of oxidation, reduction with H2 and catalytic carbonylation with CO/H2, in the microporous environment retains cluster unity and even at higher temperatures sintering is prevented. 

In 1996, it was revealed that benzylic and allylic organolithium compounds underwent carbonylation with CO aided by selenium, yielding selenol esters after trapping with alkyl halides [94]. 

With plahnum and palladium catalysts, supported on siUca, alumina and active carbon, both H2, O2 and CO probe molecules are available for dispersion measurements. For rhodium, the various values are taken from the work of Ferretti et al. [102]. For ruthenium and iridium, O2 cannot be used as a probe molecule for dispersion measurements, because there is formahon of bulk oxides. With nickel, only H2 gives reUable results, O2 and CO cannot be used as probe molecules for dispersion measurements, because there is formation of bulk oxides with O2 and metal-carbonyls with CO, but the dispersion of the sample can be additionally measured by magnetic measurements. 

It is significant that, even under such high pressures of CO, exchange of carbonyls with CO is not fast on the NMR time-scale at low temperatures. Thus, high pressure n.m.r. studies offer the possibility of structural identification of intermediates formed under extreme conditions of reactions of industrial interest and further studies of potential catalytic systems are underway. 

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