The preparation of a stable 2-pyridylboronate and its reactivity in the Suzuki-Miyaura cross-coupling reaction

The preparation and reactivity of a 2-pyridylboronate stabilised by N-phenyldiethanolamine is described. In Suzuki-Miyaura cross-coupling reactions employing this boronate, significant aryl-aryl exchange from the phosphine ligand was observed with some combinations of ligand and substrates. The amount of the exchange by-product can be minimised by appropriate choice of phosphine ligand.     

Synthesis of substituted 2-phenylhistamines via a microwave promoted Suzuki coupling

Substitutions on the 2-position of the imidazole ring of histamine have proven useful in a number of biochemical settings. Current art for the synthesis of these constructs relies upon a cumbersome and low-yielding condensation reaction. Here-in we report a new procedure for the synthesis of a series of substituted 2-phenylhistamines utilizing a microwave-promoted Suzuki coupling.     

Exploring the functionalisation of the thieno[2,3-d]pyrimidinedione core: Late stage access to highly substituted 5-carboxamide-6-aryl scaffolds

The thieno[2,3-d]pyrimidinedione core is found as a component in a range of pharmaceutically active compounds, however, synthetic approaches to these scaffolds rely on access to functionalised, highly substituted thiophenes. Here we describe a new approach for the preparation of 5-carboxamide-6-aryl analogues that involves a two-step synthesis of the thieno[2,3-d]pyrimidinedione core from a readily available mercaptouracil derivative. Thio-alkylation with ethyl 3-bromopyruvate, followed by cyclisation and dehydration mediated by polyphosphoric acid allowed the scalable synthesis of the thieno[2,3-d]pyrimidinedione unit. The late-stage functionalisation of this core motif via bromination of the thiophene ring and a subsequent Suzuki-Miyaura reaction as the key steps permitted access to a novel library of 5-carboxamide-6-aryl analogues. The physicochemical properties of these compounds were determined, generating an insight into the potential bioavailability of these scaffolds. Based on these results, a selection of the novel 5-carboxamide-6-aryl analogues were tested as lactate uptake inhibitors of monocarboxylate transporters 1, 2 and 4 in Xenopus oocytes.     

Liebeskind-Srogl cross coupling mediated synthesis of verbenachalcone

A flexible and scalable total synthesis of verbenachalcone is achieved in eight linear steps from cheap commercially available starting material, 3-(4-hydroxyphenyl)propanoic acid.     

Three-component coupling of alkynes, Baylis-Hillman adducts and sodium azide: a new synthesis of substituted triazoles

A three-component coupling was used to prepare a series of 1,4-disubstituted-1,2,3-triazoles from the corresponding acetylated Baylis-Hillman adducts, sodium azide and terminal alkynes. This one-pot reaction further increases the efficacy of ‘Click’ synthesis and diversifies the preparation of multi-functional 1,4-disubstituted-1,2,3-triazoles.     

Facile functionalization at the C2 position of a highly substituted benzofuran

To expedite an SAR study of the C2 position of a highly substituted benzofuran ring system, we developed a method for the preparation of a key precursor, iodide 10. From iodide 10, a diverse set of compounds with different substituents at the C2 position were prepared efficiently.     

A highly regioselective synthesis of 2-aryl-6-chlorobenzothiazoles employing microwave-promoted Suzuki-Miyaura coupling reaction

Suzuki-Miyaura coupling reactions of 2,6-dichlorobenzothiazole with arylboronic acids, promoted by microwave heating, efficiently produce 2-aryl-6-chlorobenzothiazoles in a highly regioselective manner. This process serves as the foundation for a simple method to rapidly construct 2-aryl-6-chlorobenzothiazole libraries.     

Synthesis of bis-8-hydroxyquinolines via an imination or a Suzuki-Miyaura coupling approach

Bis-8-hydroxyquinolines represent an important yet underexplored class of potential ligands for the preparation of various coordination polymers, which can be used in a plethora of applications. In this work, the synthesis of two types of bis-8-hydroxyquinolines, prepared via either an imination or a Suzuki-Miyaura coupling approach, as well as their analysis is discussed. Imination was pursued through the condensation of quinolinecarbaldehydes with diamines or aminoquinolines with dialdehydes, and the Suzuki-Miyaura coupling reactions were evaluated using a bromoquinoline substrate and diboronic acids.     

N-Doped porous carbon supported palladium nanoparticles as a highly efficient and recyclable catalyst for the Suzuki coupling reaction

A new catalyst, Pd particles supported on the N-doped porous carbon(PC) derived from Zn-based metal–organic frameworks(zeolitic imidazolate framework: ZIF-8), was successfully prepared for the first time.The as-prepared catalyst was designated as N-doped PC-Pd, and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscope, N_2 adsorption and inductively coupled plasma atomic emission spectroscopy. The N-doped PC-Pd composite exhibited high catalytic activity toward the Suzuki–Miyaura cross-coupling reactions. The yields of the products were in the range of 90%–99%. The catalyst could be readily recycled and reused at least 6 consecutive cycles without a significant loss of its catalytic activity.     

Stereoselective synthesis of 4-fluoro-1,3-alkadienylboronates and their application in the stereoselective synthesis of fluoropolyenes

(1E,3E)- and (1E,3Z)-4-fluoro-1,3-alkadienylboronates were stereoselectively prepared by the Heck-reaction of a vinylboronate with (E)- or (Z)-2-fluoro-1-alkenyliodonium salts, and applied to the Suzuki-Miyaura coupling reaction for the synthesis of fluoropolyenes.     

A general and efficient synthesis of substituted fluorenes and heterocycle-fused indenes containing thiophene or indole rings utilizing a Suzuki-Miyaura coupling and acid-catalyzed Friedel-Crafts reactions as key steps

A general and efficient synthesis of fluorenes or heterocycle-fused indenes including 3-thia-cyclopenta[a]indenes, 9-thia-indeno[1,2-a]indenes, 5,6-dihydroindeno[2,1-b]indoles has been developed. This methodology is realized by a multistep protocol involving first preparation of ortho-formylbiaryls through Suzuki-Miyaura coupling of o-bromobenzaldehydes with arylboronic acids or the coupling of aryl halides with 2-formylbenzene boronic acid, this is followed by Grignard addition and Friedel-Crafts cyclization reactions catalyzed by Brønsted or Lewis acid to form the desired fluorene or indene rings. The method offers several advantages such as high yields, high selectivities, mild reaction conditions, easily accessible starting materials, and so on.     

Chemo-selective Suzuki–Miyaura reactions: Synthesis of highly substituted [1,6]-naphthyridines

The Suzuki-Miyaura reaction of methyl-5-bromo-8-(tosyloxy)-1,6-naphthyridine-7-carboxylate(5),with 2 equiv. of arylboronic acids gave diarylated product, 5,8–diaryl-1,6-naphthyridine-7-carboxylate(7), whereas 1 equiv. of arylboronic acid resulted in site-selective formation of 5-aryl-8-(tosyloxy)-1,6-naphthyridine-7-carboxylate(8). The reactions proceeded with excellent chemo-selectivity in favor of the bromide group. Likewise, one-pot reaction with completely different boronic acids by sequential addition produced 1,6-naphthyridine-7-carboxylates,(10) containing two different aryl groups at 5 and 8 positions.     

Total synthesis of mycestericin A and its 14-epimer

The total synthesis of mycestericin A (1) and its 14-epimer 34 is described herein. The Overman rearrangement of an allylic trichloroacetimidate derived from l-tartrate generated a tetra-substituted carbon with nitrogen and subsequent stereoselective transformations afforded the highly functionalized left-half segment, vinyl iodide. Cross-coupling of the vinyl iodide with a chiral organometallic species synthesized from d-tartrate under the Negishi or Suzuki-Miyaura coupling conditions, followed by deprotection, completed the total synthesis of 1. The 14-epimer of mycestericin A was also synthesized, and a comparison of [α]_D values of peracetyl γ-lactone derivatives of mycestericin A and its 14-epimer as well as degradation studies of 1 and 34 fully confirmed the proposed absolute structure of mycestericin A.     

Synthesis of C1-alkyl- and acylglycals from glycals using a B-alkyl Suzuki-Miyaura cross coupling approach

A B-alkyl Suzuki-Miyaura cross coupling approach provides a flexible, efficient means to convert glycals to C1-alkylglycals and C1-acylglycals that are versatile synthetic intermediates. This approach uses readily available glycal starting materials and overcomes major limitations associated with direct alkylation or acylation of glycals. Further, a commonly observed side reaction involving reduction of the halide coupling partner is suppressed by preincubation of the borane coupling partner with aqueous base, providing new mechanistic insights into the side reaction.     

Toward the synthesis of the antibiotic branimycin: novel approaches to highly substituted cis-decalin systems

A variety of highly functionalized cis-decalin systems have been prepared by means of the stereoselective transannular Diels-Alder (TADA) reaction of a (Z,E,Z,Z)-tetraene macrolide, and by means of intramolecular nitrile oxide olefin (INOC) or ring-closing metathesis (RCM) annulations to quinic acid derivatives.     

Regioselective synthesis of substituted pyrrolopyridines based on Pd(II)-mediated cross coupling and base induced heteroannulation

Novel pyrrolopyridines have been synthesized by an efficient, regioselective and catalytic method from commercially available and inexpensive 3-aminopyridine or 2-aminopyridine.     

Base-catalyzed cross coupling of secondary alcohols and aryl-aldehydes with concomitant oxidation of alcohols to ketones: An alternative route for synthesis of the Claisen-Schmidt condensation products

Base-catalyzed C–C cross coupling of secondary alcohols and aryl-aldehydes was achieved, when an alcoholic solution of an aryl-aldehyde was stirred under reflux for 45 h in the presence of a catalytic (20 mol%) amount of K₂CO₃. The consistent formation of α,α′-bis-(benzylidene) alkanones was obtained in moderate to good yields using various secondary alcohols and substituted aryl-aldehydes. Herein, α,α′-bis-(benzylidene)alkanones, which are the classical products of Claisen-Schmidt (cross aldol) condensation, have been synthesized via an alternative strategy using secondary alcohols. Bis-(benzylidene) alkanones are an integral part of various drug regimes and the production of bis-(benzylidene) alkanones without using any precious metal is a major outcome of the present reaction.     

The reaction between 3-aminocrotonates and oxindole-3-ylidene derivatives: synthesis of highly substituted pyrroles

The reaction between 3-aminocrotonates and 3-acetonylideneoxindole in refluxing toluene resulted in 2-pyrrolo-3′-yloxindoles in high yields (around 90%). At room temperature the 2-pyrrolo-3′-yloxindoles exists as keto-enol tautomers. Treatment with POCl₃ yielded the 2-chloro-3-pyrrolyl indole, which gave the pyrrolo annulated indolopyran-2-one upon basic hydrolysis of 2-chloro-3-pyrrolyl indole methyl ester.     

Synthesis and absolute configuration of cordiaquinone K, antifungal and larvicidal meroterpenoid isolated from the Panamanian plant, Cordia curassavica

Total synthesis of cordiaquinone K, a new antifungal and larvicidal meroterpenoid, is reported. The absolute configuration of cordiaquinone K was confirmed by the synthesis.