Alkenes palladium-catalyzed carbonylation

Reviews are available on the palladium-catalyzed carbonylation of organic halides,554 dienes555 and mixtures of alkenes and organic halides.556... 

Allylic halogenides containing an additional internal functional group in a suitable position, e. g., an alkene moiety or a hydroxy group, produce the corresponding cyclopentenone derivatives or lactones, respectively, via palladium-catalyzed carbonylation [43]. Related cyclocarbonylations of cinnamyl halides or acetates to form polycyclic aromatics such as naphthol derivatives have been reported (eq. (15)). Moreover, the synthetic utility of the method was demonstrated by the synthesis of acetoxybenzofurans, acetoxyindoles, and acetoxycarbazoles [44]. 

P-Lactones can be obtained by oxidative carbonylation of alkenes in the presence of water. Ethylene, for example, is converted to p-propiolactone by carbonylation in aqueous acetonitrile at -20 C using a catalytic amount of PdCh and a stoichiometric quantity of copper(II) chloride (equation 37). Palladium-catalyzed carbonylation of halides can also be used to prepare p-lactones under mild conditions. The reaction takes place at room temperature and pressure in the presence of [PdCl2(PPh3)2] and has been applied to both bromides and chlorides (equations 38 and 39). 

In 1997, Alper and colleagues applied allenes as a special family of alkenes in palladium-catalyzed carbonylative reactions with o-iodophenols [25]. Remarkably,... 

Last year, Alexanian and Bloome described a palladium-catalyzed carbonylative Heck-type cyclization of alkyl halides [32]. The treatment of a range of primary and secondary alkyl iodides in the presence of a palladium catalyst under CO pressure yielded a variety of synthetically versatile enone products. This novel palladium-catalyzed Heck-type cyclization is a rare example where inactivated alkyl halides with -hydrogens are involved. Various substituted alkenes were well tolerated, and mono- as well as bicyclic carbocycles are easily accessed (Scheme 7.13). 

Shortly thereafter, a more general palladium-catalyzed carbonylative Heck reaction of aryl halides was able to be developed by our group [34]. For the first time, various aromatic and aliphatic alkenes were used successfully in this system, and good yields of the corresponding a,jS-unsaturated ketones were obtained (41-90 %). Starting from easily available aryl iodides and bromides, interesting building blocks were obtained under mild conditions (Scheme 7.15). With respect to the reaction mechanism, the aryl palladium complex and acyl palladium complex were characterized by X-ray, and the mechanism was studied step by step. The results fit well with DFT calculations. 

Scheme 3.11 Palladium-catalyzed carbonylative cyclization of alkenes.

Inokuchi E, Narumi T, Niida A, Kobayashi K, Tomita K, Oishi S, Ohno H, Fujii N. Efficient synthesis of trifluoromethyl and related trisubstituted alkene dipeptide isosteres by palladium-catalyzed carbonylation of amino acid derived allyUc carbonates. J. Org. Chem. 2008 73 3942-3945. 

As with carboxylic acids obtained by palladium hydroxycarbonylation, their derivatives esters, amides, anhydrides and acyl halides are synthesized from alkenes, CO and HX (X = OR, NR2 etc.). The Pd-catalyzed methoxycarbonylation is one of the most studied reactions among this type of catalyzed carbonylations and has been reviewed and included in reports of homogeneous catalysis.625, 26 The methoxycarbonylation has been applied to many different substrates to obtain intermediates in organic syntheses as well as specific products. For instance, the reaction has been applied for methoxycarbonylation of alkynes666 Highly efficient homogeneous Pd cationic catalysts have been reported and the methoxycarbonylation of alkynes has been used to develop economically attractive and environmentally benign process for the production of methyl... 

Ibuprofen (+) -2- (4-Isobutylphenyl) propionic acid Aromatic alkylation, HF-catalyzed aromatic acetylation, palladium-catlayzed carbonylation, alkene hydration... 

Palladium-catalyzed allylic oxidations, in contrast, are synthetically useful reactions. Palladium compounds are known to give rise to carbonyl compounds or products of vinylic oxidation via nucleophilic attack on a palladium alkene complex followed by p-hydride elimination (Scheme 9.16, path a see also Section 9.2.4). Allylic oxidation, however, can be expected if C—H bond cleavage precedes nucleophilic attack 694 A poorly coordinating weak base, for instance, may remove a proton, allowing the formation of a palladium rr-allyl complex intermediate (89, path by694-696 Under such conditions, oxidative allylic substitution can compete... 

Oxidation-carbonylation of 1-alkenes. These alkenes can undergo an aerobic palladium-catalyzed oxidation-carbonylation in acetic acid-acetic anhydride (4 1) with CuCl2 as a reoxidant and a trace of NaCl, required for satisfactory yields.1... 

Negishi E, Coperet C (2002) Palladium-Catalyzed Tandem and Cascade Carbopalladation of Alkynes and 1,1-Disubstituted Alkenes Terminated by Carbonylative Reactions. In Negishi E, de Meijere A (eds) Handbook of Organopalladium Chemistry for Organic Synthesis. Wiley, New York, p 1431... 

A simple synthetic method for 1,4-dicaibonyl compounds was introduced, based on the allylation of carbonyl compounds with allyl halide as a C3 component, followed by the palladium-catalyzed oxidation of the terminal alkenes (20) to methyl ketones (21). In this method, the allyl group is a synthetic equivalent of the 2-oxopropyl group (Scheme 5). This is a good anellation method for cyclopentenones. 

In a similar manner, cyclopropane-containing benzvalene can be used as the alkene component in intermolecular Pauson-Khand reactions.Several examples of intermolecular Pauson-Khand cyclizations of methylenecyclopropanes and alkynes are reported to give bicyclic car-bocycles. Ethynylcyclopropyl-substituted chromium carbonyl complexes have also been used in palladium-catalyzed coupling reactions. 

In a direct comparison of the palladium-catalyzed and the hexabutyldistannane-mediated ene-halogcnocyclization of unsaturated a-iodo carbonyl compounds, identical mixtures of regio- and stereoisomers were obtained311. Thus, it was suggested that both reactions proceed via a radical mechanism, and that palladium does not initiate an organometallic cycle via oxidative addition, alkene insertion and reductive elimination. 

The reaction of an alkene (or alkyne), CO, and H2O to directly produce a carboxylic acid is called Reppe carbony-lation chemistry or, more recently, hydrocarboxylation see Reppe Reaction). An excellent review of palladium-catalyzed Reppe carbonylation systems has been published recently by Kiss, and coverage of this important material will not be repeated here. This catalytic reaction has been known for quite some time, although the stoichiometric Ni(CO)4-based carbonylation of acetylene was the first commercial carbonylation process implemented (equation 13). The extreme toxicity of Ni(CO)4, however, has limited practical applications see Nickel Organometallic Chemistr. Co, Rh, and Pd catalysts have certainly replaced Ni(CO)4 in smaller-scale laboratory reactions, though for historical reasons a number of the fundamental mechanisms discussed in this section are based on Ni(CO)4. 

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