Facile Synthesis of Phenanthridinone Alkaloids via Suzuki–Miyaura Cross‐coupling

Phenanthridinone alkaloids crinasiadine 1 and N‐alkylcrinasiadines 6 , 7 , 8 , 9 , 10 have been synthesized based on palladium‐catalyzed tandem C–C and C–N bond formation starting from 2‐aminophenylboronic acid and 2‐bromobenzoate in short steps. Related alkaloids, 5,6‐dihydrobicolorine 2 , trisphaeridine 3 , and bicolorine 12 have also been synthesized.     

Easily Accessible 2‐(2‐Bromophenyl)‐4,4,5,5‐Tetramethyl‐[1,3,2]Dioxaborolane for Suzuki‐Miyaura Reactions

A simple and direct method has been developed for the preparation of the title compound from 1,2‐dibromobenzene. Suzuki‐Miyaura reactions of this compound with substituted bromoaryls proceeded smoothly to give 2‐bromobiphenyl derivatives in moderate to excellent yields. Instead of converting each of the bromoaryl compounds to the corresponding arylmetals followed by reacting with 2‐iodobromobenzene, the advantage of this protocol is that the substituted bromoaryls were used directly to couple with the title compound.     

Highly efficient Pd‐PEPPSI‐IPr catalyst for N‐(4‐pyridazinyl)‐bridged bicyclic sulfonamides via Suzuki–Miyaura coupling reaction

A protocol for the Suzuki–Miyaura coupling of novel 2‐(6‐chloropyridazin‐3‐yl)‐5‐(aryl/heteroarylsulfonyl)‐2,5‐diazabicyclo[2.2.1]heptanes and heteroarylboronic acids to afford variety of coupled products was realized. Pd‐PEPPSI‐IPr catalyst was found to be a powerful and reusable catalyst under relatively mild reaction conditions.     

Synthesis of a palladium complex bearing 2‐phenylbenzothiazole and its application to Suzuki–Miyaura coupling reaction

The palladacycle complex [L^sPdOAc]₂ bearing 2‐phenyl benzothiazole was synthesized and characterized by NMR and X‐ray crystallography. [L^sPdOAc]₂ was used as a catalyst in the Suzuki–Miyaura cross coupling reaction of 4‐bromotoluene with phenylboronic acid, which resulted in a conversion of >90% with 5 mol% of the Pd complex within 10 min at 60°C.     

cis‐ and trans‐2‐(4‐tert‐Butylcyclohexyloxy)‐1,3,5‐trinitrobenzene

The structures of cis‐ and trans‐2‐(4‐tert‐butyl­cyclo­hexyl­oxy)‐1,3,5‐tri­nitro­benzene, C₁₆H₂₁N₃O₇, (I) and (II), respectively, were determined at low temperature in order to obtain accurate structural parameters for comparison purposes. The C_alkyl—O_ether bond distances are 1.497 (2) and 1.491 (2) Å for (I) and (II), respectively.     

Synthesis of Arylated Benzofurans by Regioselective Suzuki–Miyaura Cross‐Coupling Reactions of 2,3‐Dibromobenzofurans‐ and 2,3,5‐Tribromobenzofurans

Arylated benzofurans were prepared by regioselective Suzuki–Miyaura cross‐coupling reactions of 2,3‐dibromobenzofuran. The reactions proceeded with very good site‐selectivity in favor of the more electron deficient position 2. The Suzuki–Miyaura reactions of 2,3,5‐tribromobenzofuran also proceeded in favor of position 2.     

Asymmetric Synthesis of the cis‐ and trans‐3,4‐Dihydro‐2,4,8‐trihydroxynaphthalen‐1(2H)‐ones

A short and efficient protocol for the asymmetric synthesis of cis‐ and trans‐3,4‐dihydro‐2,4,8‐trihydroxynaphthalen‐1(2H)‐one ( 1 and 2 , resp.) is described, with a phthalide annulation as the key step. Introduction of a OH substituent at position 2 was performed by Sharpless dihydroxylation of a silyl enol ether or by means of an N‐sulfonyloxaziridine. The absolute configuration of each isomer was determined via Mosher‐ester derivatives. By comparison with previously recorded CD spectra of our natural sample, we established that the natural trans‐ and cis‐isomers from Ceratocystis fimbriata sp. platani were the (?)‐(2S,4S)‐isomer (?)‐ 2 and the (+)‐(2S,4R)‐isomer (+)‐ 1 , respectively.     

Suzuki–Miyaura Cross‐Coupling of Potassium Organoborates with 6‐Sulfonate Benzimidazoles Using Microwave Irradiation

This article focuses on the utility of organotrifluoroborate salts as coupling partners for Suzuki–Miyaura cross‐coupling with 4‐nitro‐6‐triflyl benzimidazoles using microwave irradiation. The C–C bond formation at the 6‐position of the electron‐rich 1‐,4‐,6‐trisubstituted benzimidazole core is challenging and was not achievable via Kumada, Negishi, Stille, or Heck coupling strategies. Yields of 37–70% could be obtained via palladium coupling strategies utilizing potassium benzyl trifluoroborates as the organometallic coupling partner.     

Synthesis and photochemical properties of trans‐2‐(2‐aryl‐ or heteroarylvinyl)‐4,5‐dichloropyridazin‐3(2H)‐ones

trans‐2‐(2‐Aryl‐ or heteroarylvinyl)‐4,5‐dichloropyridazin‐3(2H)‐ones 3 were synthesized from 4,5‐dichloropyridazin‐3(2H)‐one via 2 step. The photochemical behavior of 3 in THF, methylene chloride, acetonitrile and methanol is dependent on the kind of aryl or heterocyclic ring and the solvent polarity     

Diversification of 6‐bromo‐2‐substituted Pyridine Derivatives via Suzuki‐Miyaura Cross‐Coupling

The functionalized pyridine ring is a ubiquitous moiety in numerous research areas including materials, natural products, as well as agrochemicals and is a strategic synthon for heteroaromatic synthetic method development. Pyridinyl ligand scaffolds are also frequently incorporated into the study of metal complexes for pharmaceutical applications or separation science. Convergent access to advanced synthons is critical to experimentally defining structure activity relationships and improvement of molecular performance in the aforementioned areas. The current work describes an efficient catalyst/ligand combination for accessing 2‐acetyl‐ and 2‐procarbonyl substituted pyridines via Suzuki‐Miyaura cross‐coupling with various organotrifluoroborates. Twenty examples are described with carbonyl and procarbonyl functional groups which afford subsequent access to diversified unsymmetric ketones. Substrate scope and limitation in addition to a scale up experiment are reported.     

Synthesis and antibacterial activity of novel series of 2‐(p‐tolyloxy)‐3‐(5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazol‐2‐yl)quinoline

A new series of 2‐(p‐tolyloxy)‐3‐(5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazol‐2‐yl)quinoline were synthesized from oxidative cyclization of N′‐((2‐(p‐tolyloxy)quinoline‐3‐yl)methylene)isonicotinohydrazide in DMSO/I₂ at reflux condition for 3–4 h. The structures of the new compounds were confirmed by elemental analyses as well as IR, ¹H‐NMR, and mass spectral data. All the synthesized compounds were screened for their antibacterial activities against various bacterial strains. Several of these compounds showed potential antibacterial activity. J. Heterocyclic Chem., (2011).     

Interconversion of cis‐ and trans‐Fused Oxabicyclo[5.2.0]nonan‐2‐ones

On irradiation (350 nm) in the presence of alkenes (2,3‐dimethylbut‐2‐ene, 1,1‐dimethoxyethene, and 2,4,4‐trimethylpent‐1‐ene), benzoxepinone 1 and dioxepinone 2 are converted into mixtures of cis‐ and trans‐fused oxabicyclo[5.2.0]nonan‐2‐ones. Their relative thermodynamic stabilities (as reflected by the observed diastereoisomer ratios after equilibration with basic alumina) depend on the substitution pattern of the alkene moiety.     

3‐(4‐Bromophenyl)‐5‐(4‐dimethylaminophenyl)‐1‐phenyl‐2‐pyrazoline: X‐ray and density functional theory (DFT) studies

In the crystal structure of the title compound, C₂₃H₂₂BrN₃, a strong conjugation of the pyrazoline chromophore with the aromatic rings at positions 1 and 3 is observed, as well as a significant shift in the synclinal→synperiplanar direction. The absolute structure was unequivocally determined. In the absence of clasical hydrogen‐bond donors, the structure is stabilized by weak C—H...π interactions. This paper also reports the electronic structure of the title compound using NBO (natural bond order) analysis. The contributions of lone pairs to the relevant bonds were revealed.     

Synthesis of Novel Heterocyclic Compounds with Expected Antibacterial Activities from 4‐(4‐Bromophenyl)‐4‐oxobut‐2‐enoic Acid

This research describes the utility of 4‐(4‐bromophenyl)‐4‐oxobut‐2‐enoic acid as a key starting material for preparation of a novel series of aroylacrylic acids, pyridazinones, and furanones derivatives. These heterocyclic compounds were synthesized by reaction of 4‐(4‐bromophenyl)‐4‐oxobut‐2‐enoic acid with benzimidazole, ethyl glycinate hydrochloride, anthranilic acid and o‐phenylenediamine under Aza–Michael addition conditions. Every Aza–Michael adduct was allowed to react with haydrazine hydrate and acetic anhydride to form pyridazinones and furanones derivatives, respectively. In further step, some pyridazinones were allowed to react with ethyl acetoacetate, acetyl acetone, acetyl chloride, and aromatic aldehydes to form novel heterocylces. Finally, studying antibacterial activities of these compounds was performed.     

Nanostructured Pyrophosphate Na2PdP2O7‐Catalyzed Suzuki‐Miyaura Cross‐Coupling Under Microwave Irradiation

Nanostructured palladium pyrophosphate (Na₂PdP₂O₇) catalyst was synthesized and well characterized by using different techniques (TGA, XRD, SEM, TEM....). This nanocatalyst exhibited excellent catalytic activity in the synthesis of biaryl compounds via Suzuki‐Miyaura cross‐coupling to produce their corresponding products in good to excellent yields under mild conditions. The catalyst is recyclable and was recycled for four runs for the reaction of 4‐bromoacetophenone with phenylboronic acid without appreciable loss of its catalytic activity.     

Modular Stereoselective Synthesis of (1→2)‐C‐Glycosides based on the sp2–sp3 Suzuki–Miyaura Reaction

This work reports a modular and rapid approach to the stereoselective synthesis of a variety of α‐ and β‐(1→2)‐linked C‐disaccharides. The key step is a Ni‐catalyzed cross‐coupling reaction of D ‐glucal pinacol boronate with alkyl halide glycoside easily prepared from commercially available D ‐glucal. The products of this sp²–sp³ cross‐coupling reaction can be converted to glucopyranosyl, mannopyranosyl, or 2‐deoxy‐glucopyranosyl C‐mannopyranosides by one‐ or two‐step stereoselective oxidative–reductive transformations. To the best of our knowledge, we demonstrated the first synthetic application of a challenging sp²–sp³ Suzuki‐Miyaura cross‐coupling reaction in carbohydrate chemistry.     

Palladium‐Catalyzed Suzuki–Miyaura Cross‐Coupling of Secondary α‐(Trifluoromethyl)benzyl Tosylates

A palladium‐catalyzed C(sp³)−C(sp²) Suzuki–Miyaura cross‐coupling of aryl boronic acids and α‐(trifluoromethyl)benzyl tosylates is reported. A readily available, air‐stable palladium catalyst was employed to access a wide range of functionalized 1,1‐diaryl‐2,2,2‐trifluoroethanes. Enantioenriched α‐(trifluoromethyl)benzyl tosylates were found to undergo cross‐coupling to give the corresponding enantioenriched cross‐coupled products with an overall inversion in configuration. The crucial role of the CF₃ group in promoting this transformation is demonstrated by comparison with non‐fluorinated derivatives.     

Efficient Synthesis of Sterically Hindered Arenes Bearing Acyclic Secondary Alkyl Groups by Suzuki–Miyaura Cross‐Couplings

Bulky P,P?O ligands were designed to inhibit isomerization and reduction side reactions during the cross coupling between sterically hindered aryl halides and alkylboronic acids. Suzuki–Miyaura cross‐couplings between di‐ortho‐substituted aryl bromides and acyclic secondary alkylboronic acids have been achieved with high yields. The method has also enabled the preparation of ortho‐alkoxy di‐ortho‐substituted arenes bearing isopropyl groups in excellent yields. The utility of the synthetic method has been demonstrated in a late‐stage modification of estrone and in the application to a new synthetic route toward gossypol.     

Asymmetric Suzuki–Miyaura Cross‐Coupling for the Synthesis of Chiral Biaryl Compounds as Potential Monophosphine Ligands

Efficient asymmetric Suzuki–Miyaura coupling reactions have been employed for the first time to synthesize chiral biaryl compounds with phosphinate groups as chiral auxiliaries. A series of functionalized chiral biaryls are thereby synthesized in excellent yields and good diastereoselectivities (up to >95:5 d.r.) and axially chiral monophosphorus ligands are obtained through further functionalizations.