Insertion reactions carbonylation

Single-Carbon Insertion Reactions. Carbonylation, cyanidation, and "DCME," and related reactions are convenient general processes developed to bring about the transfer of organic groups from boron to a siagle-carbon atom. 

Reactions involving the modification of ligands These reactions modify the present ligands, without adding or removing any. These include insertion reactions, carbonyl insertions (also known as alkyl migration), hydride elimination, and abstraction. 

The reaction of Grignard reagents with a carbonyl group can be understood as an insertion reaction of an unsaturated C=0 bond of the carbonyl group into... 

Naphthaleneacetic acid has also been prepared by the carbonyl-insertion reaction of 1-chloromethylnaphthalene cataly2ed by carbonyl cobalt cation (90,91). Carboxylation of 1-chloromethylnaphthalene in the presence of the catalyst Pd[P(CgH )2]2Cl2 under phase-transfer conditions gave 1-naphthaleneacetic acid in 78% yield (92). 

Bis(cyclopentadienyl)zirconium 1,3-alkadiene complexes19-20 show interesting stepwise double insertion reactions to carbonyl compounds, exploration with respect to their stereochemical features has only just begun21-23. 

Belonging to group (i) are alkylmetal carbonyls and cyclopentadienylmetal alkyl carbonyls of formula RMn(CO)5, CpFe(CO)2R, and CpMo(CO)3R. Solvent dependence of the reaction of MeMn(CO)5 with CjHi,NH2 is illustrated also in Table I. The rate varies markedly with the dielectric constant and with the nucleophilic power of the solvent. For example, on going from dimethylformamide to mesitylene, the rate of insertion is reduced by 10. Similarly, the sequence MeCN > MejCO > THF > CHCI3 > CjHj was reported for the reaction of MeMn(CO)5 with P(0CH2)3CR (R = Me and Et) in various solvents (97). Analogous trends were observed for the insertion reactions of CpFe(CO)2R and CpMo(CO)3R (48, 80, 98). 

Few quantitative data are available on the relative nucleophilicities of L toward various alkyl carbonyls. The rates of the reaction of CpMo(CO)3Me with L in toluene (Table II) decrease as a function of the latter reactant P( -Bu)3 > P( -OBu)j > PPhj > P(OPh)j, but the spread is relatively small (<8). The above order is that customarily observed for 8 2 reactions of low-valent transition metal complexes (J, 214). Interestingly, neither CpMo(CO)3Me nor CpFe(CO)2Me reacts with 1 or N, S, and As donor ligands 28, 79). This is in direct contrast to the insertion reactions of MeMn(CO)5 which manifest much less selectivity toward various L (see Section VI,B,C,D for details). 

No comparative kinetic study has been made on the same alkyl carbonyl system for two members of a given transition metal triad. Qualitative data show that the middle member is more reactive than the heaviest one e.g., CpMo(CO)jR > CpW(CO)jR (Section VI,B), Rh(III) > Ir(III) (Section VI,E), and Pd(II) > Pt(II) (Section VI,F). However, the extreme unreactivity of CpW(CO)jR and a considerable difference in lability between most alkyls of Rh(III) and Ir(III), as well as those of Pd(II) and Pt(II), have prevented detailed investigations. Surprisingly, no kinetic studies have been conducted on insertion reactions of RRe(CO)5, which would seem readily amenable to such investigations. 

Infrared Intensities of Metal Carbonyl Stretching Vibrations, 10, 199 Infrared and Raman Studies of w-Complexes, 1, 239 Insertion Reactions of Compounds of Metals and Metalloids, 5, 225 Insertion Reactions of Transition Metal-Carbon o-Bonded Compounds I Carbon Monoxide Insertion, 11, 88... 

Chapter 10 considers the role of reactive intermediates—carbocations, carbenes, and radicals—in synthesis. The carbocation reactions covered include the carbonyl-ene reaction, polyolefin cyclization, and carbocation rearrangements. In the carbene section, addition (cyclopropanation) and insertion reactions are emphasized. Recent development of catalysts that provide both selectivity and enantioselectivity are discussed, and both intermolecular and intramolecular (cyclization) addition reactions of radicals are dealt with. The use of atom transfer steps and tandem sequences in synthesis is also illustrated. 

These sites must be considered to have different catalytic properties. The sites on top (Co atoms of low coordination) would be similar to that of the central atom of cobalt carbonyl complexes, and reactions on these should be similar to those in hydroformylation. Specifically, insertion reactions between n- and cr-ligands (CO... 

Another important line of investigation concerned the carbonyl insertion reaction, which was best defined in manganese chemistry (75, 16) and extended to acylcobalt tetracarbonyls by Heck and Breslow. The insertion may be through three-membered ring formation or by nucleophilic attack of an alkyl group on a coordinated CO group. 

Owing in part to its great commercial importance, the CO insertion reaction is perhaps the most thoroughly studied metal carbonyl reaction other than substition (11-13). As shown in equation 3a, the currently... 

Prior to our studies it was recognized that ion pairing with anionic metal carbonyls could promote CO insertion and related reactions (14-16). Both kinetic and non-kinetic evidence suggests the importance of ion pairs in these types of reactions (14,17). For example, a small cation was found to greatly accelerate the CO insertion reaction relative to the same reaction with a large cation, equation 6 (14). 

Evans, D.A., Hurst, K.M., Truesdale, L.K., and Takacs, J.M., The carbonyl insertion reactions of mixed tervalent phosphorus-organosilicon reagents, Tetrahedron Lett., 2495, 1977. 

A unique Pd-catalyzed carbonyl insertion reaction of 197 furnished pyrido[2,l-b]quinazoline 198, an antiallergy agent [158]. This particular outcome may be substrate-specific. 

The overall enthalpy change of the insertion process contains contributions from four bonds (M-CO, M-COR, M-R and CO-R). As there is no significant difference between (Mn-R) and Zs(Mn-COR) then, at least in the case of manganese and hydrocarbon groups, R, the dominant factor will be the difference between T (Mn-CO) and E R-COX) [for R = CH3, E = 339 kJ mop1 (X = H), 370 kJ mol"1 (X = Cl) (Ref.23 )] which suggests that the insertion reaction is thermodynamically favoured with respect to decarbonylation. Kinetic studies of the carbonyl insertion reaction in solution have shown87) that the enthalpy of activation is 62 kj mol-1 for inser-... 

Thermolysis of 219a and 219b produced the benzofulvenes 221 as expected. However, the formation of 222 from 219c can best be accounted for by regarding the biradical 220a as the carbene 220b to allow an intramolecular C-H insertion reaction. The presence of a carbonyl group in 219 also permits the use of samarium(II) iodide, samarium(III) chloride, boron trifluoride and trifluoroacetic acid to promote the Schmittel cyclization reaction. 

Insertion takes place between a Jt-bonded fragment and a a-bonded fragment in mutual cis-positions, as was described above. The de-insertion reaction can only proceed if there is a vacant site cis to the acyl group. The experiment outlined in Figure 2.12 proves this point. A manganese acetyl complex which is labelled with 13C at the acyl carbonyl group was synthesised and heated to give de-insertion of CO. The result was that the only product formed contained the methyl substituent in a position cis to the labelled 13C. 

In this chapter we will discuss some aspects of the carbonylation catalysis with the use of palladium catalysts. We will focus on the formation of polyketones consisting of alternating molecules of alkenes and carbon monoxide on the one hand, and esters that may form under the same conditions with the use of similar catalysts from alkenes, CO, and alcohols, on the other hand. As the potential production of polyketone and methyl propanoate obtained from ethene/CO have received a lot of industrial attention we will concentrate on these two products (for a recent monograph on this chemistry see reference [1]). The elementary reactions involved are the same formation of an initiating species, insertion reactions of CO and ethene, and a termination reaction. Multiple alternating (1 1) insertions will lead to polymers or oligomers whereas a stoichiometry of 1 1 1 for CO, ethene, and alcohol leads to an ester. 

Figure 15.8 a simple example is presented of a subsequent insertion of CO and methanolysis of the palladium acyl intermediate [14], This is not a very common reaction, because both the ligand requirements and the redox conditions for Wacker and carbonylation chemistry are not compatible. For insertion reactions one would use cis coordinating diphosphines or diimines, which makes the palladium centre more electron-rich and thus the nucleophilic attack in the Wacker part of the scheme will be slowed down. In addition, the oxidants present may lead to catalytic oxidation of carbon monoxide. 

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