Hydrocarboxylation of Alkyne

In the metal-carbonyl catalysed hydrocarboxylation of alkynes ( Reppe reaction ) nearly exclusive cia-addition of H—COOH is found (Ohashi et al., 1952). 

Hydrocarboxylation of Alkynes Intramolecular addition of carboxylic acids (weak nucleophiles) to alkynes led to lactones, which were first reported by Schmidbaur et al. in the reaction of acetic add with 3-hexynes to obtain, in addition to enol ester, 3-hexanone. Traces of water were probably present in the solvent to enable the process to be carried out [99]. 

The state of the art in catalytic intermolecular additions of carboxylic acids to terminal alkynes (Scheme 27) prior to 2000 has been reviewed by Dixneuf and Bruneau, who conclude that complexes [(p-cymene)RuCl2(PR3)] are catalysts for Markovnikov additions (toluene, 80-100°C), whereas [(dppb)Ru(methallyl)2] is the preferred catalyst for anti-Markovnikov hydrocarboxylations of alkynes with predominant selectivity for (Z)-enol esters (toluene, 50-60°C) [165, 166]. 

The hydrocarboxylation of alkynes R C=CR with CO2 and (EtO)3SiH, catalysed by CuF complexes of NHC ligands (e.g. IMes and Cl2lpr), produces the ( )-configured carboxylic acids R CH=C(R )C02H. ... 

Like many carbonylation processes, the hydrocarboxylation and hydroesterification reactions were first reported by Reppe. These first reactions involved the hydrocarboxylation of alkynes. These reactions were conducted with nickel carbonyl as catalyst and occurred with very low turnover numbers. Hydrocarboxylation and hydroesterification have now been studied extensively in both academic and industrial laboratories. As a result of these investigations, commercialization of this chemistry as part of new industrial processes has occurred, and the mechanism of these processes is now generally accepted. This section of Chapter 17 presents the scope and industrial applications of hydrocarboxylation and hydroesterification, the types of catalysts that have been used for these processes, and the elementary steps that constitute the catalytic cycle for olefin and alkyne hydroesterification. 

Scheme 2.28 Regioselective tandem Sonogashira/hydrocarboxylation of alkynes [71, 72],...

The metal-complex-catalyzed hydrocarboxylation of alkynes is of value for the synthesis of a,/3-unsaturated acids and their derivatives. The direct regioselective hydrocarboxylation of alkynes to a,)8-unsaturated carboxylic acids can be achieved using the catalytic system Pd(OAc)2, dppb, and PPhj in the presence of formic acid at 120 psi of CO and 100-110 °C. The use of a mixture of the two ligands, dppb and PPh3, significantly improves the yields (Eq. 10). ... 

A tentative mechanism has been proposed for the Pd(OAc)2-catalyzed hydrocarboxylation of alkynes with formic acid (Scheme 2). Beginning with step A, the solid-state structure of Pd(OA)2 breaks down and the Pd(ll) complex is reduced to Pd(0) under CO. The catalytic species [Pd(CO) ,(PR3)] c is then formed in the presence of phosphine... 

Table 36 shows some of the reaction products obtained in the hydrocarboxylation of alkynes. The reactivity of the alkyne in the hydrocar-... 

Table 36. Hydrocarboxylation of alkynes with carbon monoxide and water...

Table 40 shows some esters obtained by hydrocarboxylation of alkynes in water/alcohol solution. 

Table 40. Unsaturated carboxylic acid esters by hydrocarboxylation of alkynes in mixtures of water and alcohols...

A DFT study has revealed the origin of the enantioselectivity in the [Cu(/ ,/ )-Ph-box](OTf)2-catalysed intramolecular aminooxygenation of iV-tosyl-2-allylanilines and 4-pentenyltosylamides to afford chiral indolines and pyrrolidines, respectively. A chairlike, seven-membered transition state with a distorted square-planar copper centre, corresponding to 5yn-aminocupration, has been proposed to produce the major enantiomer. Some light has been shed on the Cu-catalysed hydrocarboxylation of alkynes using CO2 and hydrosilanes, by DFT calculations. ... 

Li S, Yuan W, Ma S (2011) Highly regio- and stereoselective three-component nickel-catalyzed sy -hydrocarboxylation of alkynes with diethyl zine and carbon dioxide. Angew Chem Int Ed 50 2578-2582... 

K. Tani and Y. Kataoka, begin their discussion with an overview about the synthesis and isolation of such species. Many of them contain Ru, Os, Rh, Ir, Pd, or Pt and complexes with these metals appear also to be the most active catalysts. Their stoichiometric reactions, as well as the progress made in catalytic hydrations, hydroal-coxylations, and hydrocarboxylations of triple bond systems, i.e. nitriles and alkynes, is reviewed. However, as in catalytic hydroaminations the holy grail", the addition of O-H bonds across non-activated C=C double bonds under mild conditions has not been achieved yet. 

Additions. Hydrocarboxylation of alkenes" and alkynes with HCOOH under CO is accomplished by Pd catalysis. A similar reaction undergone by a propar-gylic carbonate after an S 2 process leads to an itaconic diester segment.The intermediate is converted into a cyclopentenone when the propargyl carbonate... 

Nickel A three-component hydrozincation of alkynes R C=CR with Et2Zn (3 equiv.), carried out under the atmosphere of CO2 (at normal pressure), has been shown to form ( )-conflgured hydrocarboxylation products R CH=C(R )C02H in the presence of (COD)2Ni as a catalyst (l-3mol%) and CsF (1 equiv.) in MeCN at 60 °C over 1.5h.i ... 

Hydrocarboxylation of alkenes or alkynes involves the formal addition of a carboxylic acid O—H bond across a C=C or C=C bond (Scheme 2.25) [63]. In particular, intramolecular hydrocarboxylation provides an atom economical strategy for lactone synthesis. The aforementioned reaction is thermodynamically favorable but there is a large intrinsic kinetic barrier for this type of cydization, thus requiring the addition of a catalyst. Catalysts for hydrocarboxylation typically facilitate addition by alkene or alkyne binding. This process increases the inherent electrophilicity of the C=C and C=C bonds, respectively. Subsequent protonolysis (or 3-H elimination under Pd catalysis) regenerates the catalytic spedes. 

The catalytic hydrocarbonylation and hydrocarboxylation of olefins, alkynes, and other TT-bonded compounds are reactions of important industrial potential.Various transition metal complexes, such as palladium, rhodium, ruthenium, or nickel complexes, have widely been used in combination with phosphines and other types of ligands as catalysts in most carbonylation reactions. The reactions of alkenes, alkynes, and other related substrates with carbon monoxide in the presence of group VIII metals and a source of proton affords various carboxylic acids or carboxylic acid derivatives.f f f f f While many metals have successfully been employed as catalysts in these reactions, they often lead to mixtures of products under drastic experimental conditions.f i f f f In the last twenty years, palladium complexes are the most frequently and successfully used catalysts for regio-, stereo-, and enantioselective hydrocarbonylation and hydrocarboxylation reactions.f ... 

Table 37. Allenic acids by hydrocarboxylation of oL-halogenafed alkynes...

Principally the described ester synthesis can be achieved with the same metal carbonyl catalysts as used in the hydrocarboxylation. Recently the catalyst systems Pd/HCl, PdClg [446] and Pd/HI [447] have been reported to be very effective. These catalysts are suitable for converting the less reactive acetylene carboxylic acid esters. In analogy to cobalt catalysts, Pd causes a double hydrocarboxylation of the alkynes ... 

Catalytic carboxylation of internal alkynes with CO2 has been achieved in the presence of Ni [50] or Cu [51] catalysts, and through a hydrocarboxylative pathway, not involving the intermediacy of a metaUaoxacyclopentenone, but, as previously noted for the hydrocarboxylation of alkenes (see Sect. 5.3), implying the intermediate formation of an M—H catalyticaUy active species, which may easily be generated in the reactimi mixture using diethylzinc [50] or hydrosilanes [51] as hydride transfer agent. 

Zhang Y, Riduan SN (2011) Catalytic hydrocarboxylation of alkoies and alkynes with C02-Angew Chem Int Ed 50 6210-6212... 

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