Suzuki-Miyaura cross-coupling of alkenyl tosylates with alkenyl MIDA boronates

A practical procedure for the palladium-catalysed Suzuki-Miyaura coupling of various alkenyl tosylates with alkenyl MIDA boronates has been developed. Commercially available trans-bromo[N-succinimidyl-bis(triphenylphosphine)]palladium(II) [Pd(PPh₃)₂NBS] is an effective catalyst under the slow release conditions of MIDA boronates; with less activated alkenyl tosylates addition of the cheap, air-stable tricyclohexylphosphine tetrafluoroborate enhances reactivity.     

Synthesis and biological activity of 2-aminoimidazole triazoles accessed by Suzuki-Miyaura cross-coupling

A pilot library of 2-aminoimidazole triazoles (2-AITs) was synthesized and assayed against Acinetobacter baumannii and methicillin-resistant Staphylococus aureus (MRSA). Results from these studies show that these new derivatives have improved biofilm dispersal activities as well as antibacterial properties against A. baumannii. With MRSA biofilms they are found to possess biofilm inhibition capabilities at low micromolar concentrations.     

Regioselective synthesis of polysubstituted pyrazoles and isoxazoles

A regioselective synthesis has been developed for the preparation of unsymmetrical 1,3,5-triaryl-4-alkylpyrazolines and -pyrazoles by treatment of alpha-benzotriazolyl-alpha,beta-unsaturated ketones with monosubstituted hydrazines followed by alkylation at the 4-position of the pyrazoline ring. Reaction of alpha-benzotriazolyl-alpha,beta-unsaturated ketones with hydroxylamine gives 3,5-disubstituted isoxazoles regioselectively.     

One-pot reductive amination and Suzuki-Miyaura cross-coupling of formyl aryl and heteroaryl MIDA boronates in array format

Formyl-substituted aryl and heteroaryl MIDA boronates were prepared by a DMSO-free method and used in the first reported one-pot reductive amination-Suzuki-Miyaura cross-coupling sequence. This sequence was then carried out in parallel array format, using microwave-assisted in situ release cross-coupling of MIDA boronates to generate a library with diversity along two axes, affording rapid and convenient access to an array of druglike molecules.     

Palladium-catalyzed Suzuki-Miyaura cross-coupling reaction of organoboronic acids with N-protected 4-iodophenyl alanine linked isoxazoles

Suzuki-Miyaura coupling reaction of N-protected 4-iodopheyl alanine isoxazoles with arylboronic acids, catalyzed by palladium, efficiently produce benzyl-N-(4-bipheyl)-2-(3-methyl-5(E)-2-aryl-1-ethenyl-4- isoxazolyl)-amino-2-oxoethyl) carba-mates in good yields. This process is first of its kind to construct carbon-carbon bond formation having biaryl motif on amino acid linked isoxazole moiety.     

Azidosubstituted arylboronic acids: synthesis and Suzuki-Miyaura cross-coupling reactions

Arylboronic acids having a remote azido group were prepared from the corresponding azidosubstituted aryl bromides via lithiation and treatment with trialkyl borates. Preparative yields were achieved when the starting aryl bromides possessed ortho-alkoxy groups, which would stabilize the intermediate aryllithium species. Conventional Suzuki cross-coupling of the arylboronic acids proceeded generally well with retention of azido group; however, sometimes azidomethyl fragment underwent oxidative transformation into a nitrile.     

Solid-phase synthesis of 5-arylhistidines via a microwave-assisted Suzuki-Miyaura cross-coupling

Microwave irradiation efficiently promoted the solid-phase Suzuki-Miyaura reaction of a 5-bromohistidine with various arylboronic acids in the presence of a palladium catalyst. This methodology allowed the synthesis of peptides bearing a histidine residue substituted at position 5 of the imidazole ring with a phenyl, a substituted phenyl, a pyridyl, or a thienyl ring, as well as with the benzene ring of a tyrosine residue.     

Expedient synthesis of 4-O-methylhonokiol via Suzuki-Miyaura cross-coupling

Concise and practical synthesis of 4-O-methylhonokiol was achieved in 34% overall yield. The key features of our synthesis include chemoselective ortho-mono bromination of phenol as well as biaryl formation via Suzuki-Miyaura cross-coupling, in which bromophenol was reacted with potassium aryltrifluoroborate using Pd(OAc)₂ and RuPhos under microwave conditions.     

Suzuki-Miyaura cross-coupling of potassium trifluoroboratohomoenolates

Ketone-, ester-, and amide-containing potassium trifluoroboratohomoenolates were prepared in good to excellent yields from the corresponding unsaturated carbonyl compounds. They were shown to be effective coupling partners in the Suzuki-Miyaura reaction with a variety of electrophiles including electron-rich and electron-poor aryl bromides and -chlorides.     

Highly fluoroalkylated amphiphilic triazoles: Regioselective synthesis and evaluation of physicochemical properties

A series of fluoroalkylated amphiphilic 1,2,3-triazoles was synthesised by efficient 1,3-dipolar cycloaddition of 2-perfluoroalkyl-ethyl-azides, prepared from commercial 2-perfluoalkyl-1-iodoethanes, and acetylenic esters or acids. The synthesis was accomplished by heating in acetone or by microwave irradiation. Excellent regioselectivity was observed for dissymmetrical alkynes. Physicochemical study shows surfactant behaviour.     

Convenient synthesis of selected meta- and ortho-substituted pentaarylpyridines via the Suzuki-Miyaura cross-coupling reaction

The first synthesis of sterically demanding, stable at room temperature atropisomeric derivatives of penta-(ortho-substituted phenyl)pyridines is described. The Suzuki-Miyaura cross-coupling reaction of pentabromopyridine and selected meta- and ortho-tolylboronic acids afforded a series of pentaarylpyridine derivatives. The structures of two room temperature stable atropisomeric derivatives of penta-(o-tolyl)pyridines were confirmed by single-crystal X-ray analysis. Racemic atropisomers were examined by ¹H NMR spectroscopy with a chiral solvating agent in order to visualize the presence of individual enantiomers.     

Suzuki-Miyaura cross-coupling reactions of potassium alkenyltrifluoroborates

We have previously reported that the palladium-catalyzed cross-coupling reaction of air-stable potassium alkenyltrifluoroborates with aryl halides and triflates proceeds readily with good yields. Recent progress in outlining the scope and limitations of such reactions is described herein. The palladium-catalyzed cross-coupling reaction of potassium alkenyltrifluoroborates with aryl and heteroaryl halides and triflates proceeds readily with moderate to excellent yields. The alkenyl cross-coupling reaction can generally be effected using 2 mol % of PdCl2(dppf).CH2Cl2 as catalyst in i-PrOH-H2O in the presence of t-BuNH2 as the base. A variety of functional groups are tolerated in both partners, and the process is stereospecific with regard to the alkenyltrifluoroborate starting material.     

Microwave assisted asymmetric Suzuki-Miyaura and Negishi cross-coupling reactions: synthesis of chiral binaphthalenes

Microwave assisted asymmetric Suzuki-Miyaura and Negishi enantioselective cross-coupling reactions are reported for the first time, and have been applied to the rapid synthesis of chiral sterically hindered binaphthalene derivatives in reasonable to excellent yields (65–96%) and fair to good enantioselectivities (43–70% ee).     

Regioselective palladium cross-coupling of 2,4-dihalooxazoles: convergent synthesis of trisoxazoles

A regioselective Suzuki-Miyaura cross-coupling of 2,4-dihalooxazoles followed by a Stille coupling has been successfully developed. The procedure affords convergent syntheses of trisoxazoles in high yield and in a minimum number of steps.     

Exploring the selectivity of the Suzuki-Miyaura cross-coupling reaction in the synthesis of arylnaphthalenes

A series of 1-arylnaphthalenes and 1,8-diarylnaphthalenes were synthesized by the Suzuki-Miyaura cross-coupling methodology showing significant differentiation in the yields and selectivity between aryl rings with electron donating (higher yields), and electron withdrawing substituents (lower yields). These results strongly support the relation between the nucleophilicity of the boronate complex and its reactivity, and emphasize the importance of the transmetalation step in the overall efficiency of this cross-coupling reaction. The results obtained with non-symmetric 1,8-diarylnaphthalenes indicate preference for arylation of an already arylated species (the 1-aryl-8-bromonaphthalene intermediate) over mono-arylation of 1,8-dibromonaphthalene. Evidences for the existence of intramolecular Pd?π and aromatic interactions in some Pd(II) complexes were found.     

One-pot synthesis of trisubstituted conjugated dienes via sequential Suzuki-Miyaura cross-coupling with alkenyl- and alkyltrifluoroborates

The sequential, stereoselective disubstitution of 1,1-dibromoalkenes using a variety of alkenyltrifluoroborates followed by alkyltrifluoroborates in the presence of Pd(PPh3)4 is described. This synthetic method proceeds smoothly in one pot under mild reaction conditions to provide the corresponding trisubstituted, conjugated dienes in excellent yield. Moreover, the method is operationally very simple because the organotrifluoroborates are stable in air, and the byproducts are innocuous inorganic salts.     

Synthesis of S-acetyl oligoarylenedithiols via Suzuki-Miyaura cross-coupling

Oligoarylenes with three or four aromatic rings, bearing two S-acetylated mercaptomethyl groups in 1,3 position on one end of the polyaromatic system and presenting various functionalities on the other terminal ring, have been synthesized by the Suzuki-Miyaura cross-coupling reaction. The use of palladium complexes with a Buchwald's phosphine as ligand allowed us to perform this coupling reaction also in the presence of benzylic S-acetyl-protected functionalities on the aromatic halide. The obtained oligoarylenes are potential novel candidates for the generation of self-assembling monolayers on metal substrates.     

Synthesis of biphenylamines via Suzuki-Miyaura cross-coupling reactions

A small library of meta- and para-biphenylamines substituted by various alkyl, alkoxy, phenoxy, or halogeno groups on their aromatic rings was synthesized via Suzuki-Miyaura cross-coupling between bromoanilines and arylboronic acids using palladium catalysts. The experimental conditions were carefully adjusted to accommodate a wide range of substituents, in terms of electron-withdrawing or -donating ability and steric bulk. In some cases, protection and deprotection of the amine function via its trifluoroacetamide were added to the reaction sequence in order to facilitate the cross-coupling step.     

Site-selective Suzuki-Miyaura cross-coupling reactions of 2,3,4,5-tetrabromofuran

Suzuki-Miyaura reactions of 2,3,4,5-tetrabromofuran allow a convenient and site-selective synthesis of mono-, di- and tetraarylfurans which are not readily available by other methods.