Synthesis and Functionalization of Indoles Through Palladium-catalyzed Reactions

Cacchi, Sandro; Fabrizi, Giancarlo

doi:10.1021/cr040639b

Cited by 1,708 publications

(369 citation statements)

References 319 publications

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“…Improved conversion (46%) was observed using NaOt-Bu, in the cross-coupling of 11 with 4-iodonitrobenzene; however, potassium tert-butoxide (KOt-Bu) provided only a 3% yield of the desired cross-coupling product With a successful activator in hand, palladium sources were then surveyed ( Table 2, entry 4). Interestingly, it was found that the palladium(0) source Pd 2 (dba) 3 •CHCl 3 was superior to the palladium(II) sources surveyed. With 5 mol % of Pd 2 (dba) 3 •CHCl 3 the cross-coupling reaction of 11 gave complete (99%) conversion to the product ( Table 2, entry 7).. Interestingly reaction times were much longer using Pd 2 (dba) 3 •CHCl 3 , in comparison to Pd 2 (dba) 3 ; however, the simple addition of 0.05 equiv of CHCl 3 to the reaction mixture containing Pd 2 (dba) 3 provided comparable results to the chloroform solvate.…”

Section: Cross-coupling Of Silanols and Silanolatesmentioning

confidence: 99%

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Palladium-Catalyzed Cross-Coupling of Five-Membered Heterocyclic Silanolates

2008

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The preparation of π-rich 2-aryl heterocycles by palladium-catalyzed cross-coupling of sodium heteroarylsilanolates with aryl iodides, bromides and chlorides is described. The cross-coupling process was developed through extensive optimization of the follow key variables: (1) identification of stable, isolable alkali metal silanolates, (2) identification of conditions for preformation and isolation of silanolate salts, (3) judicious choice in the palladium catalyst/ligand combination, and (4) selection of the protecting group on the nitrogen of indole. It was found that the alkali metal silanolates, either isolated or formed in situ, offered a significant rate enhancement and broader substrate scope over the use of silanols activated by Brønsted bases such as NaOt-Bu. In addition, the optimized conditions for the cross-coupling of 2-indolylsilanolates were readily applied to the cross-coupling of 2-pyrrolyl-, 2-furyl-, and 2-thienylsilanolates.

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Section: Cross-coupling Of Silanols and Silanolatesmentioning

confidence: 99%

“…1,7 Some of the more venerable methods include sigmatropic rearrangements of phenyl hydrazones 8 or [2,3]-sigmatropic rearrangements of e-mail: denmark@scs.uiuc.edu. sulfonium ylides.…”

Section: Introductionmentioning

confidence: 99%

Palladium-Catalyzed Cross-Coupling of Five-Membered Heterocyclic Silanolates

2008

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“…10 Bromide 1a undergoes oxidative addition with Pd(0) to form the arylpalladium intermediate A. Subsequently, this undergoes CO insertion to produce an acylpalladium intermediate B, which react with nucleophile 3a to produce intermediate C in the presence of Et 3 N. The reductive elimination of intermediate C is interrupted by the coordination of 2a to give the π-alkyne(acyl)palladium intermediate D. 11 Insertion then occurs to form intermediate E, which gives a Pd(0) species and product 4a through reductive elimination. …”

Section: Scheme 4 Palladium-catalyzed Carbonylative Addition Reactionmentioning

confidence: 99%

Synthesis of Enaminones by a Palladium-Catalyzed Four-Component Carbonylative Addition Reaction

Wang

Chen

et al. 2017

Synlett

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A palladium-catalyzed carbonylative addition reaction of aryl bromides, amines, and alkynes has been developed. The reaction occurs readily in N,N-dimethylformamide with PdCl 2 (PPh 3 ) 2 as a catalyst to give the corresponding enaminones in medium to excellent yields. Furthermore, a mechanism for the palladium-catalyzed four-component carbonylative addition reaction is proposed.Key words palladium catalysis, multicomponent reaction, carbonylative addition, enaminones, aryl bromides, amines For economic and environmental reasons, environmentally friendly chemistry has attracted considerable attention in modern organic synthesis. 1 Multicomponent reactions (MCRs) 2 can produce target products directly by simple operations with high efficiency and with reduced waste generation compared with conventional methods in organic synthesis. 3 Palladium-catalyzed carbonylation is a representative MCR 4 that has played an important role in the synthesis of carbonyl compounds because of its high selectivity and mild reaction conditions. In recent years, palladium-catalyzed three-component carbonylative coupling reactions of aryl halides with organometallic reagents, alkenes, alkynes, amines, alcohols, water, or hydrogen have been studied. 5 However, much to our regret, there have been few reports on palladium-catalyzed four-component carbonylations. 6 Recently, Wu and co-workers reported a palladium-catalyzed four-component carbonylation for the synthesis of 4(3H)-quinazolinones or thiochromenones. 7 In 2014, Bao and co-workers reported the palladium-catalyzed threecomponent carbonylative addition reaction using 1,4-bis(diphenylphosphino)butane (DPPB) as a ligand in DMF. 8 In the present study, we found that the reductive elimination of the acylpalladium amine intermediate was interrupted by coordination of an alkyne and that a carbonylative addition reaction of an aryl bromide, CO, an amine, and an alkyne successfully occurred with PdCl 2 (PPh 3 ) 2 as catalyst at 120 °C in DMF (Scheme 1), thereby providing an efficient and novel strategy for the synthesis of enaminones. 9 The method has several prominent advantages over conventional methods, such as mild reaction conditions, high efficiency, simple starting materials, and straightforward operations. Scheme 1 Palladium-catalyzed four-component one-pot synthesis of enaminonesInitially, we began our study by using 1-(4-bromophenyl)ethanone (1a, 0.5 mmol), ethynylbenzene (2a, 0.6 mmol), HNEt 2 (3a, 0.75 mmol), and CO (5 atm) as substrates and PdCl 2 (5 mol%) as a catalyst to optimize the reaction conditions. The expected reaction occurred, and 1-(4-acetylphenyl)-3-(diethylamino)-3-phenylprop-2-en-1-one (4a) was obtained in 20, 22, and 45% yields in the presence of the bidentate ligands DPPB, 1,3-bis(diphenylphosphino)propane (DPPP), and 1,2-bis(diphenylphosphino)ethane (DPPE) respectively (Table 1, entries 1-3). To our delight, however, the isolated yield of product 4a improved to 86% when PPh 3 was used as the ligand in DMF solvent (entry 4). A decreased yield of 4a...

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“…Due to high electron density at position 3, indole undergoes electrophilic substitutions at position 2 and 3, respectively. A variety of synthetic methods for the indole ring system have been developed for the past hundred years [12][13][14][15] . The palladium-catalyzed annulation of 2-haloanilines with alkynes, in particular, is of great importance due to the easy availability of substrates 16 .…”

Section: Introductionmentioning

confidence: 99%

A Novel Synthesis of [4-(3-Methyl-1H-Indol-2-Yl)Phenyl]Phenylmethanone

Suhana¹,

Rȧjeswari²

2017

Orient. J. Chem

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We have developed a simple route for the synthesis of [4-(3-methyl-1H-indol-2-yl)phenyl](phenyl)methanone from easily available starting materials. The (4-propylphenyl) phenylmethanone was prepared by Friedel Craft's benzoylation of n-propyl benzene with benzoyl chloride in dichloromethane using aluminium chloride as the Lewis acid catalyst. Side chain bromination with N-bromo succinimide in tetra chloro methane furnished the bromo derivative which on oxidation with bis-tetra butyl ammonium dichromate gave 1, 4-diacyl benzene. The target molecule was obtained through Fischer indole cyclisation of the diacyl benzene namely 1-(4-benzoylphenyl)propan-1-one via the formation of the hydrazone, followed by cyclization in presence of boron trifluoride ethyl etherate in acetic acid. The structure of the target molecule was elucidated by IR, H 1 , C 13 NMR, Mass spectroscopy and elemental analysis. This method proves to be an efficient route for the synthesis of [4-(3-methyl-1H-indol-2-yl)phenyl](phenyl)methanone in high yields, thereby facilitating the generation of potential biologically active compounds.

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Synthesis and Functionalization of Indoles Through Palladium-catalyzed Reactions

Cited by 1,708 publications

References 319 publications

Palladium-Catalyzed Cross-Coupling of Five-Membered Heterocyclic Silanolates

Palladium-Catalyzed Cross-Coupling of Five-Membered Heterocyclic Silanolates

Synthesis of Enaminones by a Palladium-Catalyzed Four-Component Carbonylative Addition Reaction

A Novel Synthesis of [4-(3-Methyl-1H-Indol-2-Yl)Phenyl]Phenylmethanone

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