Pd-catalyzed Carbonylation Research Articles

A phosphine-free Pd catalyst for the selective double carbonylation of aryl iodides

The first phosphine-free Pd-catalysed double carbonylation of aryl iodides is reported as a general and practical method, giving excellent conversions and selectivities for a wide range of aryl iodides and amine nucleophiles under atmospheric CO pressure.

Carbonylation of Nitrobenzene in Methanol with Palladium Bidentate Phosphane Complexes: An Unexpectedly Complex Network of Catalytic Reactions, Centred around a Pd–imido Intermediate

The reactivity of palladium complexes of bidentate diaryl phosphane ligands (P(2)) was studied in the reaction of nitrobenzene with CO in methanol. Careful analysis of the reaction mixtures revealed that, besides the frequently reported reduction products of nitrobenzene [methyl phenyl carbamate (MPC), N,N'-diphenylurea (DPU), aniline, azobenzene (Azo) and azoxybenzene (Azoxy)], large quantities of oxidation products of methanol were co-produced (dimethyl carbonate (DMC), dimethyl oxalate (DMO), methyl formate (MF), H(2)O, and CO). From these observations, it is concluded that several catalytic processes operate simultaneously, and are coupled via common catalytic intermediates. Starting from a P(2)Pd(0) compound formed in situ, oxidation to a palladium imido compound P(2)Pd(II)=NPh, can be achieved by de-oxygenation of nitrobenzene 1) with two molecules of CO, 2) with two molecules of CO and the acidic protons of two methanol molecules, or 3) with all four hydrogen atoms of one methanol molecule. Reduction of P(2)Pd(II)=NPh to P(2)Pd(0) makes the overall process catalytic, while at the same time forming Azo(xy), MPC, DPU and aniline. It is proposed that the Pd-imido species is the central key intermediate that can link together all reduction products of nitrobenzene and all oxidation products of methanol in one unified mechanistic scheme. The relative occurrence of the various catalytic processes is shown to be dependent on the characteristics of the catalysts, as imposed by the ligand structure.

Synthesis of 3-Indazolecarboxylic Esters and Amides via Pd-Catalyzed Carbonylation of 3-Iodoindazoles

A straightforward and effective procedure for the preparation of 1H-indazole-3-carboxylic acid esters and amides was developed. A series of functionalized 3-iodoindazoles were subjected to Pd-catalyzed carbonylations in the presence of methanol or amines, yielding the title compounds in moderate to good yield. For the majority of examples, the reaction proceeded cleanly under mild conditions, which were readily tolerated by a diverse range of functional groups that allow further synthetic transformations.

Palladium-Catalyzed Approach to Primary Amides Using Nongaseous Precursors

A simple protocol is reported for the preparation of primary aryl amides under Pd-catalyzed carbonylation chemistry applying a two-chamber system with crystalline and nontransition metal based sources of carbon monoxide and ammonia. The method is suitable for the synthesis of a number of primary amides with good functional group tolerance. Incorporation of (13)CO into the primary amide group was also found to be effective making this approach useful for accessing carbon isotope labeled derivatives.

Pd-Catalyzed Carbonylation of Diazo Compounds at Atmospheric Pressure: A Catalytic Approach to Ketenes

The carbonylation of carbenes through catalytic cycles is highly desirable due to the importance of ketene-mediated reactions in organic synthesis. In this investigation, a highly efficient and mild catalytic approach toward ketene intermediates has been developed based on Pd-catalyzed carbonylation of diazo compounds with CO. When α-diazocarbonyl compounds or N-tosylhydrazone salts are heated in the presence of a palladium catalyst under atmospheric pressure of CO, ketene intermediates are formed in situ, where they undergo further reactions with various nucleophiles such as alcohols, amines, or imines. The Pd-catalyzed tandem carbonylation-Staudinger cycloaddition gives β-lactam derivatives in good yields with excellent trans diastereoselectivity. The results from DFT calculation on the reaction mechanism suggest that Pd is involved in the [2 + 2] cycloaddition process and affects the diastereoselectivity of the β-lactam products by assisting isomerization of the addition intermediate. On the other hand, the acylketenes generated from the Pd-catalyzed carbonylation of α-diazoketones react with imines in a formal [4 + 2] cycloaddition manner to afford 1,3-dioxin-4-one derivatives. This straightforward carbonylation provides a new approach toward highly efficient catalytic generation of ketene species under mild conditions.

Pd-Catalyzed Carbonylative Reactions of Aryl Iodides and Alkynyl Carboxylic Acids via Decarboxylative Couplings

Alkynyl carboxylic acids reacted with aryl iodides under a CO atmosphere in the presence of a palladium catalyst to produce α,β-alkynyl aryl ketones in good yields. The maximum turnover number was 16 800. The desired carbonylative coupling was formed from phenyl propiolic acid without any formation of a noncarbonylative coupling product in the absence of CuI. However, the reaction with alkyl-substituted alkynyl carboxylic acids required CuI as a cocatalyst for high yield.

Highly regioselective palladium-catalysed oxidative allylic C–H carbonylation of alkenes

Pd-catalysed direct oxidative carbonylation of allylic C-H bonds with carbon monoxide was first described. This new procedure shows that the inherent requirement for a leaving group in the Tsuji-Trost palladium-catalysed allylic carbonylation can be lifted, which provides a new route for accessing more synthetically useful β-enoic acid esters with high regioselectivity.

Tandem Pd-Catalyzed Carbonylation and Intramolecular Vinyl Allene Diels−Alder Reaction toward Galiellalactone Analogues

A novel route toward new galiellalactone analogues via a tandem palladium-catalyzed carbonylation and intramolecular Diels-Alder reaction of a dienyne carbonate is presented.

ChemInform Abstract: A Convenient Synthesis of 4-Aminomethyl-L-phenylalanine.

Abstract N-Boc-4-Aminomethyl-L-phenylalanine is prepared from N-Boc-4-Iodophenylalanine in 78% yield over three steps. The method features an efficient Pd-catalyzed carbonylation, oxime formation, and subsequent catalytic reduction employing an ethanol/water/acetic acid solvent system which is crucial to successful reaction.

ChemInform Abstract: Synthesis of (5.5.5.5)Fenestranes by Pd-Catalyzed Carbonylation- Cyclization.

ChemInform Abstract: Synthesis of (5.5.5.5)Fenestranes by Pd-Catalyzed Carbonylation- Cyclization.

Dipeptidyl-Quinolone Derivatives Inhibit Hypoxia Inducible Factor-1α Prolyl Hydroxylases-1, -2, and -3 with Altered Selectivity

Intracellular levels of the hypoxia-inducible transcription factor (HIF) are regulated under normoxic conditions by prolyl hydroxylases (PHD1, 2, and 3). Treatment of cells with PHD inhibitors stabilizes HIF-1α, eliciting an artificial hypoxic response that includes the transcription of genes involved in erythropoiesis, angiogenesis, and glycolysis. The different in vivo roles of the three PHD isoforms are not yet known, making a PHD-selective inhibitor useful as a biological tool. Although several chemical series of PHD inhibitors have been described, significant isoform selectivity has not been reported. Here we report the synthesis and activity of dipeptidyl analogues derived from a potent but non-selective quinolone scaffold. The compounds were prepared by Pd-catalyzed reductive carbonylation of the 6-iodoquinolone derivative to form the aldehyde directly, which was then attached to a solid support via reductive amination. Amino acids were coupled, and the resulting dipeptidyl-quinolone derivatives were screened, revealing retention of PHD inhibitory activity but an altered PHD1, 2, and 3 selectivity profile. The compounds were found to be ∼10-fold more potent against PHD1 and PHD3 than against PHD2, whereas the specific parent compound had shown no appreciable selectivity among the different PHD isoforms.

Oxalyl chloride as carbonyl synthon in Pd-catalyzed carbonylations of triarylbismuth and triarylindium organometallic nucleophiles

Oxalyl chloride has been demonstrated to function as C1 carbonyl synthon in the carbonylations of triarylbismuth and triarylindium nucleophiles under palladium-catalyzed conditions. All the three aryl groups from both bismuth and indium reagents participated in carbonylative couplings to afford the corresponding functionalized ketones in high yields. This study also disclosed a novel utilization of oxalyl chloride as facile alternative source of CO for carbonylations under palladium catalysis.

ChemInform Abstract: Development of a Method for the Synthesis of α-Substituted α,β-Unsaturated Lactones Based on Stille-Type Pd-Catalyzed Carbonylation of (Z)-ω-Iodoalkenols. An Efficient and Selective Synthesis of (+)-Hamabiwalactone B.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Pd-catalysed oxidative carbonylation of amino alcohols to N,N′-bis(hydroxyalkyl)ureas under mild conditions using molecular oxygen as the oxidant

A very simple method has been developed for the selective synthesis of symmetrical N,N′ -bis(hydroxyalkyl)ureas, OC[NH-(CH 2) x -OH] 2 ( x = 3–6), by oxidative carbonylation of α,ω-amino alcohols [3-aminopropanol (3-AP), 4-aminobutanol (4-AB), 5-aminopentanol (5-APe), 6-aminohexanol (6-AH)] with CO/O 2 mixtures (O 2 = 5 mol%) in the presence of Pd(II)/ligand/NEt 3·HI catalytic systems. The catalytic process takes place under very mild conditions ( p(CO/O 2) = 0.1 MPa; 303–333 K). The target products can be isolated in high yield through a very simple and straightforward procedure. The catalytic system can be easily recovered and recycled for several times. The influence of a few reaction parameters (nature of ancillary ligand and iodide co-catalyst, I/Pd molar ratio, etc.) on the catalytic activity has also been investigated and the main mechanistic features of the catalytic process fully elucidated.

One-pot amide synthesis from allyl or benzyl halides and amines by Pd-catalysed carbonylation

Amides can be prepared from allyl or benzyl halides and primary or secondary amines, using Pd(0) catalyst under CO pressure, in a one-pot synthesis. The reaction proceeds through the acyl palladium halide formation which undergoes an acylic nucleophilic substitution from the amine.

Convergent synthesis of stereodefined exo-alkylidene-gamma-lactams from beta-halo allylic alcohols.

A convergent process for the assembly of stereodefined mono- and bicyclic exo-alkylidene-gamma-lactams is described that proceeds through the union of beta-halo allylic alcohols, aromatic imines, and CO. Overall, regio- and stereoselective Ti-mediated reductive cross-coupling, followed by Pd-catalyzed carbonylation, can be performed in a one- or two-pot procedure, defining a highly selective three-component coupling process for heterocycle synthesis.

Palladium-catalyzed carbonylation reactions of aryl bromides at atmospheric pressure: a general system based on Xantphos.

A method for the Pd-catalyzed carbonylation of aryl bromides has been developed using Xantphos as the ligand. This method is effective for the direct synthesis of Weinreb amides, primary and secondary benzamides, and methyl esters from the corresponding aryl bromides at atmospheric pressure. In addition, a putative catalytic intermediate, (Xanphos)Pd(Br)benzoyl, was prepared and an X-ray crystal structure was obtained revealing an unusual cis-coordination mode of Xantphos in this palladium-acyl complex.

Palladium-Catalyzed Thiocarbonylation of Iodoarenes with Thiols in Phosphonium Salt Ionic Liquids

Trihexyl(tetradecyl)phosphonium hexafluorophosphate, a phosphonium salt ionic liquid (PSIL) is a particularly effective general reaction media for the Pd-catalyzed carbonylation reaction of iodoarenes and thiols to form thioesters. Recycling of the ionic liquid containing active Pd-catalyst was also demonstrated.

Palladium‐Catalyzed Aminocarbonylation of Aryl Chlorides at Atmospheric Pressure: The Dual Role of Sodium Phenoxide

No pressure, no worries: A general, functional-group-tolerant, mild system for the Pd-catalyzed carbonylation of aryl chlorides to the corresponding amides has been developed. The catalyst operates at 1 atm CO using an inexpensive, air-stable, and commercially available ligand (see scheme, Cy=cyclohexyl). Sodium phenoxide is a critical additive in this transformation; its role has been studied using in situ IR spectroscopy.

An Efficient Catalyst for Pd‐Catalyzed Carbonylation of Aryl Arenesulfonates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.