Palladium-catalyzed aminosulfonylation of aryl halides

The palladium-catalyzed three-component coupling of aryl iodides, sulfur dioxide, and hydrazines to deliver aryl N-aminosulfonamides is described. The colorless crystalline solid DABCO·(SO(2))(2) was used as a convenient source of sulfur dioxide. The reaction tolerates significant variation of both the aryl iodide and hydrazine coupling partners.     

Palladium-catalyzed Suzuki cross-coupling of aryl halides with aryl boronic acids in the presence of glucosamine-based phosphines

Carbohydrate-substituted phosphines are easily obtained in quite good yields by coupling of protected or non-protected d-glucosamine with the corresponding diphenylphosphino acid. These neutral ligands, in association with palladium acetate, are very active catalysts in the Suzuki cross-coupling reaction. The polyhydroxy phosphines are more active than the peracetylated phosphines. The process tolerates electron-rich as well as electron-poor substituents. Excellent turnovers, up to 97?000 are observed.     

Palladium-catalyzed cross-coupling of benzyl thioacetates and aryl halides

A method for preparing benzyl aryl thioethers utilizing an in situ deprotection of benzyl thioacetates as an alternative to free thiols as starting materials has been developed and optimized. Good to excellent yields of diverse benzyl aryl thioethers are obtained with air-stable, odor-free, and easy to prepare thioesters. A one-pot protocol for forming benzyl aryl thioethers from a benzyl halide, potassium thioacetate, and an aryl bromide has also been demonstrated.     

Palladium-catalyzed intermolecular coupling of aryl halides and amides

[formula: see text] The first general intermolecular C-N bond-forming reactions between aryl halides and amides were realized using a palladium catalyst with Xantphos as the ligand. Aryl triflates, carbamates, and sulfonamides are also viable substrates for the amidations, which proceed at 45-110 degrees C with 1-4 mol% of Pd catalyst in 66-99% yields and exhibit good functional group compatibility.     

Palladium-catalyzed amination of aryl halides on solid support

[reaction: see text] The first examples of the Pd(0)-catalyzed amination of aryl halides using Rink-resins as nitrogen source are described. Pd(2)dba(3)/BINAP/NaO-t-Bu was found to be the most efficient catalyst/base system, while a solvent mixture of dioxane and tert-butyl alcohol was shown to enhance the selectivity toward the desired monoarylation. Moderate to good yields and excellent purities of the amination products were found with electron-poor aryl halides, while electon-rich aryl halides failed to react under these conditions.     

Palladium-catalyzed direct arylation of nitro-substituted aromatics with aryl halides

Direct arylation reactions of nitrobenzenes and aryl halides occur in good yield and high ortho regioselectivity. These reactions can be performed on gram scale with as few as 3 equiv of the nitro arene relative to the aryl halide. The synthetic utility of this method is demonstrated via rapid synthesis of a Boscalid intermediate.     

Palladium-catalyzed C-N cross coupling of sulfinamides and aryl halides

The palladium-catalyzed C-N cross coupling of sulfinamides and aryl halides is reported. In the presence of Pd(2)(dba)(3), tBuXPhos, NaOH, and a small amount of water, the C-N cross coupling of chiral tert-butanesulfinamide and aryl halides was accomplished to give N-aryl tert-butanesulfinamide without racemization, and the coupling of racemic p-toluenesulfinamide smoothly afforded N-aryl p-toluenesulfinamides. 2-Bromopyridine was also suitable for the coupling. Addition of a small amount of water to the catalytic system was of importance to obtain high yields.     

Palladium-catalyzed aminations of aryl halides with phosphine-functionalized imidazolium ligands

A series of 1-(2-diphenylphosphinoferrocenyl)ethyl-3-substituted imidazolium iodides [3-substituent = methyl (1a); isopropyl (1b); tert-butyl (1c); 1-adenosyl (1d); cyclohexyl (1e); 2,6-dimethylphenyl (1f); 2,4,6-trimethylphenyl (1g); 2,6-diisopropylphenyl (1h)] have been prepared and evaluated as ligands in the palladium-catalyzed aminations of aryl halides with various amines. The scope of the coupling process was carried out for various aryl bromides and chlorides with the catalysts generated in situ from a mixture of Pd(OAc)2 and in the presence of a base. NaO t Bu was found the choice of base in combination with dioxane, toluene, or DME as solvent, although NaOH or Cs2CO3 promoted the coupling of 4-bromotoluene with morpholine in moderate conversion. The steric hindrance from the 3-substituent of imidazolium in the hybrid-bidentate chelating system was found to be only beneficial to the substrates without ortho-substituents. The more sterically hindered 1d or 1h promoted the coupling of bromobenzene with morpholine in nearly quantitative conversion with 0.2 mol% of palladium loading in the presence of NaO t Bu at 110 degrees C, and 94% of conversion was afforded with the less sterical demanding 1a for a longer time. However, for the substrates with ortho-substituents, higher conversions were achieved with 1a. The Pd(OAc)2/1d catalytic system was also active for deactivated aryl chloride, and 71% isolated yield for the desired product was realized for coupling of 4-chloroanisole with morpholine at 2 mol% of catalyst loading. The developed catalyst system has been applied successfully to the synthesis of a key building block for a type of functional polymers.     

Palladium-catalyzed nitromethylation of aryl halides: an orthogonal formylation equivalent

An efficient cross-coupling reaction of aryl halides and nitromethane was developed with the use of parallel microscale experimentation. The arylnitromethane products are precursors for numerous useful synthetic products. An efficient method for their direct conversion to the corresponding oximes and aldehydes in a one-pot operation has been discovered. The process exploits inexpensive nitromethane as a carbonyl equivalent, providing a mild and convenient formylation method that is compatible with many functional groups.     

Palladium-catalyzed cross-coupling of cyclopropanols with aryl halides under mild conditions

Intra- and intermolecular palladium-catalyzed cross-coupling of cyclopropanols with aryl halides can be achieved in good yields under mild conditions.     

Palladium-catalyzed carbonylative coupling of pyridine halides with aryl boronic acids

The carbonylative Suzuki cross-coupling of a variety of mono-iodopyridines and bromopyridines (1a,b, 3a-c, 5) catalyzed by palladium-phosphane systems has been studied to prepare benzoylpyridine derivatives (2, 4, 6). The selectivity and the rate of the reaction are highly dependent on the reaction conditions, i.e. nature of the palladium catalyst precursor, solvent, temperature and CO pressure. The main side-products arise from direct, non-carbonylative cross-coupling. Under optimized conditions, benzoylpyridines are recovered in high yields (80-95%). The order of reactivity decreases from iodo- to bromopyridines and from 2-, 4- to 3-substituted halopyridines. The reactivity of dihalopyridines has been investigated; 2,6-dibromopyridine (7) and 3,5-dibromopyridine (11) are selectively transformed into either the corresponding benzoyl-phenylpyridine (8, 12) or the corresponding dibenzoylpyridine (9, 13). Dissymmetric 2,5-dihalopyridines (15a,b) are transformed into 2-benzoyl-5-bromopyridine (16) or 2,5-dibenzoylpyridine (17) in high yields.     

Palladium-catalyzed cross-coupling reaction of tricyclopropylbismuth with aryl halides and triflates

The palladium-catalyzed cross-coupling reaction of tricyclopropylbismuth with aryl and heterocyclic halides and triflates is reported. The reaction tolerates numerous functional groups and does not require anhydrous conditions. The method was successfully extended to the cross-coupling of triethylbismuth.     

Palladium-catalyzed cross-coupling reactions of 2-indolyldimethylsilanols with substituted aryl halides

[reaction: see text] A mild and general cross-coupling reaction of 2-indolylsilanols has been developed. The experimental variables that lead to successful coupling are (1) the use of sodium tert-butoxide as the activator, (2) the use of copper(I) iodide in stoichiometric quantities, and (3) the use of Pd2(dba)3.CHCl3 as the catalyst. Under these conditions N-(Boc)-2-indolyldimethylsilanol reacts with a variety of aromatic iodides to afford the coupling products in good yield (70-84%).     

Palladium-catalyzed regiocontrolled alpha-arylation of trimethylsilyl enol ethers with aryl halides

Inter- and intramolecular arylations of trimethylsilyl enol ethers with aryl halides are accomplished regiospecifically in the presence of a palladium catalyst and tributyltin fluoride in refluxing benzene or toluene. The optimal catalyst system called for the use of Pd2(dba)3 and tri-tert-butylphosphine in ca. 1:2 ratio. Aryl iodides, bromides, and chlorides are all effective arylation partners in this reaction. [reaction: see text]     

Palladium-catalyzed benzylic direct arylation of benzyl sulfones with aryl halides

An effective palladium catalyst system for the direct arylation of benzyl sulfones with aryl halides has been developed. The catalytic reaction provides a facile route to diarylmethyl sulfones. The products can be transformed further via desulfonylative functionalization mediated by aluminum compounds.     

Palladium-catalyzed phenylation and vinylation of aryl halides in aqueous media

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, p. 2672, November, 1990.     

Palladium-catalyzed homocoupling of aryl halides in the presence of fluoride

This report describes the fluoride-mediated homocoupling of aryl iodides and bromides catalyzed by palladium(0). This coupling protocol is tolerant of electron-donating and electron-withdrawing substitutents on the aryl halide, as well as ortho substitution. Optimum reaction conditions entail 10 mol% Pd(dba)₂, 3 equiv of tetrabutyl ammonium fluoride (TBAF) in DMF at 90 °C.     

Palladium-catalyzed decarboxylative coupling of potassium nitrophenyl acetates with aryl halides

A palladium-catalyzed decarboxylative cross-coupling of potassium 2- and 4-nitrophenyl acetates with aryl chlorides and bromides has been developed. Because the nitro group can be readily converted to many other functional groups, the new reaction provides a useful method for the preparation of diverse 1,1-diaryl methanes and their derivatives.