Palladium-catalyzed Aminocarbonylation Research Articles

High-yielding synthesis of deepened cavitands bearing picolyl moieties on the upper rim

Conventional high-yielding reactions (such as etherification, condensation reactions) and palladium-catalysed aminocarbonylation served as highly efficient synthetic tools for the synthesis of novel cavitands bearing Schiff-base and carboxamide/2-ketocarboxamide functionalities, respectively. In this way, two families of deepened cavitands with related structures possessing 2-, 3- and 4-picolylamine moieties on the upper rim have been synthesised. Unexpectedly high chemoselectivities towards tetracarboxamides and tetrakis(2-ketocarboxamides) have been observed. The aminocarbonylation of tetraiodocavitand as an iodoaromatic substrate proved to be highly selective in two aspects: (i) no substantial formation of either the mono-, di- or trifunctionalized products was observed and (ii) no ‘mixed’ products possessing both carboxamide and 2-ketocarboxamide fragments, due to selective simple and double carbon monoxide insertion, were detected.

Palladium-catalyzed diaminocarbonylation: synthesis of androstene dimers containing 3,3′- or 17,17′-dicarboxamide spacers

Novel androstene-based dimers linked through A- and D-ring with 3,3′- and 17,17′-dicarboxamide spacers, were synthesized via palladium-catalyzed aminocarbonylation. Androstane derivatives possessing either 3-iodo-3,5-diene or 17-iodo-16-ene functionality were used as substrates in the presence of palladium-phosphine in situ catalysts and aliphatic and aromatic diamines as N-nucleophiles. Since androst-4-ene-3,17-dione was used as starting material, a multistep synthesis including protection/deprotection of one of the keto functionalities (3-one or 17-one) as ethylene ketals, transformation of the other keto group to iodoalkene functionality via its hydrazone, and palladium-catalyzed aminocarbonylation of the iodoalkene functionality was used. In this way, new dimeric compounds possessing a keto functionality were obtained in moderate-to-good isolated yields, via highly chemoselective reactions, under relatively mild conditions.

Palladium-catalyzed aminocarbonylation of alkynes to succinimides.

Succinimide derivatives are useful building blocks for the synthesis of natural products and drugs. We describe an efficient route to succinimide derivatives comprising Pd(xantphos)Cl2-catalyzed aminocarbonylation of alkynes with aromatic or aliphatic amines in the presence of p-TsOH. The utility of this route is demonstrated with the synthesis of a large number of succinimide compounds including an important photochromic molecule.

Diastereoselective aminocarbonylation of a steroidal iodoalkene with 2,2′-diamino-1,1′-binaphthalene in palladium-catalysed reactions

A palladium-catalysed aminocarbonylation of a steroidal iodoalkene (17-iodo-5α-androst-16-ene) model compound with 2,2′-diamino-1,1′-binaphthalene as an N-nucleophile was carried out. The combination of a steroidal skeleton possessing central elements of chirality and a binaphthyl moiety with axial chirality was carried out resulting in a novel type of steroidal carboxamides. The binaphthalene—steroid conjugates are potential 5α-reductase inhibitors. Both epimers of the monocarboxamide and those of the dicarboxamide, formed with moderate diastereoselectivity, were isolated and fully characterised.

ChemInform Abstract: Palladium‐Catalyzed Aminocarbonylation of Aryl Iodides with Amides and N‐Alkyl Anilines.

A novel and efficient palladium-catalyzed aminocarbonylation of aryl iodides with amides and N-alkyl anilines has been developed. The reaction tolerates a wide range of functional groups and is a reliable method for the rapid synthesis of a variety of valuable imides and tertiary benzanilides under an atmospheric pressure of CO.

Alkoxycarbonylpiperidines as N-nucleophiles in the palladium-catalyzed aminocarbonylation

Piperidines possessing ester functionality, such as 2-(methoxycarbonyl)piperidine (methyl pipecolinate), 3-(ethoxycarbonyl)piperidine (ethyl nipecotate), and 4-(ethoxycarbonyl)piperidine (ethyl isonipecotate), were used as N-nucleophiles in palladium-catalyzed aminocarbonylation of iodobenzene and iodoalkenes such as 1-iodocyclohexene and 17-iodoandrost-16-ene. While the aminocarbonylation of both iodoalkenes, carried out under mild reaction conditions, resulted in the exclusive formation of the carboxamide, the same reaction of iodobenzene brought about the mixture of the corresponding carboxamide and 2-ketocarboxamide. The chemoselectivity toward the latter compounds, formed via double carbonyl insertion, was substantially increased by using high carbon monoxide pressure (up to 40 bar). Carboxamides derived from iodoalkenes and ketocarboxamides derived from iodoarene have been obtained in moderate to high yields.

ChemInform Abstract: A Phosphine‐Free Approach to Primary Amides by Palladium‐Catalyzed Aminocarbonylation of Aryl and Heteroaryl Iodides Using Methoxylamine Hydrochloride as an Ammonia Equivalent.

The palladium-catalyzed synthesis of primary amides by aminocarbonylation of aryl and heteroaryl iodides under phosphine-free conditions is reported for the first time. Methoxylamine hydrochloride, acting as an ammonia equivalent, undergoes sequential carbonylation and demethoxylation under mild reaction conditions. The procedure does not require a phosphine ligand and takes place in short reaction times at low temperatures to provide the products in excellent yields.

Synthesis of N-picolylcarboxamides via palladium-catalysed aminocarbonylation of iodobenzene and iodoalkenes

A systematic investigation of the palladium-catalysed aminocarbonylation of iodobenzene, 1-iodocyclohexene and 1′-iodostyrene in the presence of N-nucleophiles containing pyridyl moieties (2-, 3- and 4-picolylamine, N-ethyl-4-picolylamine, di-(2-picolyl)amine) was carried out. The two types of iodo substrates differ substantially regarding the selectivity towards carbonylation: while the aminocarbonylation of iodobenzene resulted in the formation of carboxamide and ketocarboxamide mixtures under various conditions, with the predominant formation of ketocarboxamide even at low carbon monoxide pressure, the aminocarbonylation of iodoalkenes under same conditions gave the corresponding unsaturated carboxamide exclusively. Most of the carboxamides and phenylglyoxylamides, obtained via single and double carbon monoxide insertion, respectively, were isolated in yields of synthetic interest (up to 86%). Low reaction rates and unexpected chemoselectivity towards carboxamide formation have been observed with di-(2-picolyl)amine as N-nucleophile in the aminocarbonylation of iodobenzene.

Palladium-catalyzed aminocarbonylation of aryl iodides with amides and N-alkyl anilines.

A novel and efficient palladium-catalyzed aminocarbonylation of aryl iodides with amides and N-alkyl anilines has been developed. The reaction tolerates a wide range of functional groups and is a reliable method for the rapid synthesis of a variety of valuable imides and tertiary benzanilides under an atmospheric pressure of CO.

Synthesis and Evaluation of a 18F-Labeled Diarylpyrazole Glycoconjugate for the Imaging of NTS1-Positive Tumors

Aiming to image NTS1 overexpressing tumors, the diarylpyrazole glycoconjugate 8, derived from the potent NTS1 antagonist SR142948A, was synthesized taking advantage of the palladium-catalyzed aminocarbonylation reaction. The glycoconjugate 8 displayed excellent affinity and selectivity toward NTS1. Radiosynthesis proceeded straightforwardly, obtaining [(18)F]8 with excellent stability and highly beneficial biodistribution in vivo as demonstrated by PET imaging in HT29 tumor-bearing nude mice. Thus, the tracer [(18)F]8 represents a highly promising candidate for PET imaging of NTS1-positive tumors.

A Phosphine-Free Approach to Primary Amides by Palladium-Catalyzed Aminocarbonylation of Aryl and Heteroaryl Iodides Using Methoxylamine Hydrochloride as an Ammonia Equivalent

The palladium-catalyzed synthesis of primary amides by aminocarbonylation of aryl and heteroaryl iodides under phosphine-free conditions is reported for the first time. Methoxylamine hydrochloride, acting as an ammonia equivalent, undergoes sequential carbonylation and demethoxylation under mild reaction conditions. The procedure does not require a phosphine ligand and takes place in short reaction times at low temperatures to provide the products in excellent yields.

Palladium-catalyzed carbonylative synthesis of N-cyanobenzamides from aryl iodides/bromides and cyanamide

A novel and convenient protocol for the synthesis of N-cyanobenzamides starting from readily available aryl halides and cyanamide via palladium-catalyzed aminocarbonylation has been developed. The protocol utilizes Mo(CO)6 as the CO source or CO(gas) and affords the desired N-cyanobenzamides in moderate to good yields.

Synthesis of novel 13α-18-nor-16-carboxamido steroids via a palladium-catalyzed aminocarbonylation reaction

13α-18-nor-16-Carboxamido steroids were synthesized via a palladium-catalyzed aminocarbonylation reaction of the corresponding iodoalkenes. The starting material was an unnatural 13α-16-keto steroid, obtained by a Wagner–Meerwein rearrangement of a 16α,17α-epoxide in the presence of [BMIM][BF4]. The 13α-16-keto steroid was converted to a mixture of 16-iodo-16-ene and 16-iodo-15-ene derivatives in two steps by Barton’s methodology. Aminocarbonylation of the steroidal alkenyl iodides was carried out using different primary and secondary amines as nucleophiles. The products, 16-carboxamido-16-ene and 16-carboxamido-15-ene derivatives, were obtained in good yields and were characterized by 1H and 13C NMR, IR and MS.The reduction of the above two unsaturated carboxamides resulted in the same product, 17α-methyl-16α-carboxamido-androstane.

Sequential one-pot synthesis of benzoxazoles from aryl bromides: successive palladium- and copper-catalyzed reactions

A convenient one-pot process has been developed for the synthesis of benzoxazoles. Starting from aryl bromides and 1,2-dibromobenzenes palladium-catalyzed aminocarbonylation and subsequent copper-catalyzed coupling reaction gave a variety of substituted benzoxazoles in moderate to good yields.

A systematic approach to the synthesis of androstane-based 3,17-dicarboxamides (homo- and mixed dicarboxamides) via palladium-catalyzed aminocarbonylation

3,17-Dicarboxamido-androst-3,5,16-triene derivatives possessing various amine moieties were synthesized under mild conditions using palladium-catalyzed homogeneous aminocarbonylation as key reaction. Compounds containing the corresponding iodoalkene functionalities, i.e., 17-iodo-16-ene and 3-iodo-3,5-diene structural motifs, were used in the aminocarbonylation and the N-nucleophiles were varied systematically. Three amines, such as tert-butylamine, piperidine and methyl alaninate were used as N-nucleophiles in the aminocarbonylation. All variations of 3,17-dicarboxamides were synthesized using this methodology.Androst-4-ene-3,17-dione was used as starting material. The synthetic strategy of the multistep synthesis was based on the systematic variation and consecutive use of three different reactions: (i) the protection/deprotection of one of the keto functionalities (3-one or 17-one) as ethylene ketals, (ii) the transformation of the other keto group to iodoalkene functionality via its hydrazone, and (iii) palladium-catalyzed aminocarbonylation of the iodoalkene functionality.

High-yielding synthesis of 1-carboxamido-3,4-dihydronaphthalenes via palladium-catalyzed aminocarbonylation

1-Iodo-3,4-dihydronaphthalene, an iodoalkene substrate obtained from α-tetralon, has been carbonylated in the presence of palladium–phosphine precatalysts. Systematic investigations have revealed that the 1-carboxamido-3,4-dihydronaphthalenes and 1-methoxycarbonyl-3,4-dihydronaphthalene have been formed in exceptionally high isolated yields (up to 96%) in chemospecific reaction. The influence of the amine nucleophile and that of the reaction conditions (carbon monoxide pressure, reaction temperature) on the reactivity of the substrate have been investigated.

Palladium-Catalyzed Synthesis of Benzimidazoles and Quinazolinones from Common Precursors

N-(o-Halophenyl)imidoyl chlorides and the corresponding imidates are easily prepared and can be utilized as complementary precursors for the synthesis of important heterocycles. The synthesis of N-substituted benzimidazoles was possible from the palladium-catalyzed reaction of both classes of substrate with a variety of N-nucleophiles. The use of the imidate precursor for the synthesis of N-substituted quinazolinones by incorporation of a palladium-catalyzed aminocarbonylation reaction has also been demonstrated. Both processes tolerate a wide range of functional groups.

New conjugated dienamides via palladium-catalyzed selective aminocarbonylation of enynes

New conjugated dienamides have been synthesized effectively via palladium-catalyzed aminocarbonylation of enynes in the presence of various amines, diaminoalkanes, and aminoalcohols. The products have been utilized as substrates in alkoxycarbonylation reactions using methanol as the nucleophile and Pd(PPh3)2Cl2 as the catalyst to afford novel ω-amidoesters in high yields and selectivities. Interestingly, the product obtained from the alkoxycarbonylation reaction of the dienamide product of enyne 1b was observed to undergo carbonylation of the α,β-double bond with respect to the carbonyl group and isomerization of the second isolated double bond.

Functionalization of the pyridazin-3(2H)-one ring via palladium-catalysed aminocarbonylation

5-Iodo- and 4,5-dibromo-2-methylpyridazin-3(2H)-ones were aminocarbonylated in the presence of various amines including amino acid methyl esters in a palladium-catalysed reaction. The iodo derivative afforded the corresponding amides with complete conversion and high isolated yields. The dibromo derivative has shown unexpectedly high reactivity in this reaction, resulting in 4,5-dicarboxamides using primary amines as N-nucleophiles. Monoaminocarbonylation has not been observed, i.e., neither 4-bromo-5-carboxamide nor 4-carboxamido-5-bromo derivatives have been formed. However, the use of secondary amines such as piperidine and morpholine resulted in the formations of mixtures of amino-substituted bromopyridazinones. That is, no carbon monoxide insertion took place in these cases. Some mechanistic details of the formation of aminocarbonylation and amination products are also discussed.

An efficient route for the synthesis of chiral conduritol-derivative carboxamides via palladium-catalyzed aminocarbonylation of bromocyclohexenetetraols

A family of chiral conduritol-derivative carboxamides was synthesized through palladium-catalyzed aminocarbonylation of diastereoisomeric bromocyclohexenetetraols, previously prepared through biotransformation of bromobenzene by mutant strains of Pseudomonas putida F39/D.The coupling reactions of bromocyclohexenetetraols with CO and different amines, such as tert-butylamine, aniline, and piperidine, were performed in the presence of in situ generated Pd(0)/PPh3 catalyst. The methodology was applied to the corresponding iodo-cyclohexenetetraol derivative, using (L)-alanine and (L)-valine methyl ethers as N-nucleophiles. The resulting carboxamides were obtained in highly chemoselective reactions, isolated, and fully characterized.