Palladium-catalyzed Coupling Reactions of Aryl Halides

4 Palladium-catalyzed Coupling Reactions of Aryl Halides 

Palladium-catalyzed coupling reactions of aryl halides or triflates with vinylic compounds are of paramount importance for the generation of sp -sp carbon 

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The 2,3-substituted indols are formed via a palladium-catalyzed coupling reaction of aryl halide, o-alkenylphenyl isocyanide, and amine (Equation (122)).481 Oxidative addition of an aryl halide, insertion of both the isonitrile and alkene moieties of o-alkenylphenyl isocyanide, and 1,3-hydrogen migration may form a 7r-allylpalladium species, which is then attacked by an amine to afford an indol. 

Alkylboronic acids and arylboronic acids, RB(OH)2, and ArB(OH)2, respectively, are increasingly important in organic chemistry. The palladium catalyzed coupling reaction of aryl halides and aryl triflates with arylboronic acids (the Suzuki-Miyaura... 

Recently, Buchwald and Hartwig have developed the palladium-catalyzed coupling reaction of aryl halides with amines (Scheme 165), and they have extended this reaction to the intramolecular version to give a variety of the aza-heterocyclic compounds 547 (Scheme 166).231 This methodology has provided a wide variety of alkaloids, such as indoles,232 inda-zoles,233 benzimidazoles,234 benazepines,235 phena-zines,236 carbapenems,237 the mitomycin ring system,238 a-carbolines,239 and polyheterocycles.240 Pharmacologically active natural products, such as (—)-asperlicin (550) (Scheme 167),241 dehydrobufotenine (553) (Scheme 168),242 and makaluvamine C... 

Zapf A, Beller M (2005) The development of efficient catalysts for palladium-catalyzed coupling reactions of aryl halides. Chem Commnn 431 40... 

Bumagin, N.A., More, P.G. and Beletskaya, I.P. (1989) Synthesis of substituted cinnamic acids and cinnamonitriles via palladium-catalyzed coupling reactions of aryl halides with acrylic acid and acrylonitrile in aqueous media. J. Organomet. Chem., 371, 397-401. 

In 2005, The Development of EfQcient Catalysts for Palladium-Catalyzed Coupling Reactions of Aryl Halides, by Zapf and Beller [104]. 

This article presents the principles known so far for the synthesis of metal complexes containing stable carbenes, including the preparation of the relevant carbene precursors. The use of some of these compounds in transition-metal-catalyzed reactions is discussed mainly for ruthenium-catalyzed olefin metathesis and palladium-Znickel-catalyzed coupling reactions of aryl halides, but other reactions will be touched upon as well. Chapters about the properties of metal- carbene complexes, their applications in materials science and medicinal chemistry, and their role in bioinorganic chemistry round the survey off. The focus of this review is on ZV-heterocyclic carbenes, in the following abbreviated as NHC and NHCs, respectively. 

The reaction can be performed at room temperature with various heteroaryl halides (Equation 73) <20050L697>. It was found that (2-pyridyl)allyldimethylsilanes are pyridyl-transfer reagents in palladium-catalyzed coupling reactions of aryl iodides in the presence of silver oxide as an activator <20060L729>. 

The synthesis of 1-alkenylboronic acids from l-alkenylmagnesiums or -lithiums suffers from difficulty in retaining the stereochemistry of 1-aikenyl halides, but the palladium-catalyzed coupling reaction of diboron 82 with 1-aikenyl halides or tri-flates directly provides 1-alkenylboronic esters (Scheme 1-43) [157, 158]. Although the reaction conditions applied to the aryl coupling resulted in the formation of an... 

Palladium-catalyzed cyclization reactions with aryl halides have been used to synthesize pyrazole derivatives. V-Aryl-lV-(c>-bromobenzyl)hydrazines 26 participated in a palladium-catalyzed intramolecular amination reaction to give 2-aryl-2W-indazoles 27 . Palladium-catalyzed cascade intermolecular queuing-cyclocondensation reaction of o-iodophenol (28) with dimethylallene and aryl hydrazines provided pyrazolyl chromanones 29 <00TL7129>. A novel one-pot synthesis of 3,5-disubstituted-2-pyrazolines 32 has been achieved with an unexpected coupling-isomerization sequence of haloarene 30, propargyl alcohol 31, and methylhydrazine <00ACIE1253>. 

The added advantage of the C (1 )-stannylated glycals is their abUity to participate in palladium-catalyzed coupling reactions with organic halides, a process independently reported by Beau [75] and Friesen [81]. Vinyl stannane 237 can be benzylated, allylated or acylated provided that appropriate catalysts are used [75,77] and representative examples are given in Scheme 59. The C-arylation of... 

Cross-coupling reaction of aryl halides with arylamines is a straightforward method for forming a carbon-nitrogen bond and is catalyzed by a palladium complex. This methodology was applied by Kanbara, Mullen, and several groups to... 

Wang L, Zhang Y, Liu L et al (2006) Palladium-catalyzed homocoupling and cross-coupling reactions of aryl halides in poly(ethylene glycol). J Org Chem 71(3) 1284-1287... 

Carbon—carbon coupling reactions of aryl halides are commonly catalyzed by palladium triarylphosphine complexes and proceed well for aryl bromides and iodides while aryl chlorides are generally unreactive. More basic chelating trialkylphosphines, however, render palladium sufficiently electrophilic to undergo rapid oxidative addition with chlorobenzene ... 

It has been demonstrated that fluorovinylzinc reagents undergo stereoselective palladium-catalyzed coupling reactions with aryl (e.g., formation of 2 " ), vinyl (e.g., formation of heteroaryl, alkanoyl. and alkoxycarbonyl halides. Fluorovinylzinc reagents also undergo allyl-ation (e.g., formation of 4 ), halogenation, oxidative dimerization, and protonation reactions. ... 

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