Organoboronic Acids Research Articles

Gram‐Scale Synthesis of β‐(Hetero)arylethenesulfonyl Fluorides via a Pd(OAc)2 Catalyzed Oxidative Heck Process with DDQ or AgNO3 as an Oxidant

AbstractA practical oxidative Heck reaction between organoboronic acids and ethenesulfonyl fluoride (ESF) is developed. Aryl‐ and heteroaryl‐boronic acids react efficiently and stereoselectively with ESF in the presence of a catalytic amount of Pd(OAc)2 and 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ) or AgNO3 in AcOH to afford the corresponding E‐isomer of β‐arylethenesulfonyl fluoride products. The utility of this reaction is exemplified by an expanded scope of 47 examples including N‐, O‐, and S‐containing heteroaromatics, demonstrating chemoselectivity over aryliodides, and gram‐scale operation without the requirement for strict anhydrous or oxygen‐free conditions. Furthermore, this procedure discriminates against the formation of arylboronic acids homo‐coupling byproducts. In addition, the preparation of the first aryl vinylsulfonate polymer, a material with functionalizable Michael acceptor sites, from a starting arylboronic acid is described.magnified image

Nickel-Catalyzed Intermolecular Carbosulfonylation of Alkynes via Sulfonyl Radicals.

β,β-Disubstituted vinyl sulfones were obtained with complete regio- and stereocontrol in a multicomponent reaction involving alkynes, organoboronic acids, and sulfonyl chlorides in the presence of a nickel catalyst. The reaction proceeds via sulfonyl radicals generated in situ under mild reaction conditions.

Nickel‐Catalyzed Intermolecular Carbosulfonylation of Alkynes via Sulfonyl Radicals

Abstractβ,β‐Disubstituted vinyl sulfones were obtained with complete regio‐ and stereocontrol in a multicomponent reaction involving alkynes, organoboronic acids, and sulfonyl chlorides in the presence of a nickel catalyst. The reaction proceeds via sulfonyl radicals generated in situ under mild reaction conditions.

Silver‐Catalyzed Atom‐Economic Hydrophosphorylation of Propargyl Epoxides: An Access to 4‐Phosphoryl 2,3‐Allenols and Stereodefined 1‐Phosphoryl 1,3‐Dienes

AbstractThe highly regioselective nucleophilic ring opening of propargyl epoxides by P(O)H compounds based on a silver catalyst is reported. A variety of P(O)H compounds including H‐phosphonates, H‐phosphinates and diarylphosphine oxides can be used to produce 4‐phosphoryl 2,3‐allenols under mild conditions. The stereoselective synthesis of 1‐phosphoryl 1,3‐butadienes from 4‐phosphoryl 2,3‐allenols and organoboronic acids via a palladium‐catalyzed coupling reaction is also described.magnified image

Electrochemical Properties and Reactions of Organoboron Compounds

Organoboron compounds are highly useful in various fields such as synthetic organic chemistry, pharmaceutical chemistry, and materials chemistry as well as analytical chemistry. However, there have been limited reports dealing with their electrochemical properties and reactions to date.1-3) Quite recently, we found marked negative shifts of the oxidation potentials of alkyl and aryboronic acids and their esters in the presence of fluoride ions compared with those in the absence of fluoride ions. 4-8) It was also clarified that negative shift was derived from the formation of negatively charged boron-ate complex with fluoride ions. In this talk, we focus on our new finding of the β-effect of organoboronic acid esters having a heteroatom or unsaturated bond at their α-position, which is more pronounced compared with that of the corresponding organosilicon compounds. 5,6,8) Anodic radical coupling of organotrifluoroborates7) and substitutions of organoboronic acid esters with oxygen nucleophiles have been achieved. 4-8) Thus, we have shown that boryl groups work as electroauxiliaries like silyl groups.

Silver-catalyzed carbon–selenium cross-coupling usingN-(phenylseleno)phthalimide: an alternate approach to the synthesis of organoselenides

Silver(I) catalyzed phenylselenylation of terminal alkynes and organoboronic acids has been demonstrated using N-(phenylseleno)phthalimide as an electrophilic SePh donor. A wide variety of terminal alkynes and organoboronic acids are selenylated efficiently to produce the corresponding alkynyl and diaryl selenides, respectively, in good yields. Silver(I) acts as a Lewis acid in this process.

Short synthesis of polyfunctional sp3-rich threonine-derived morpholine scaffolds.

A convenient synthesis of novel complex morpholines was achieved by a two-step process involving a Petasis three-component coupling reaction of glycolaldehyde, organoboronic acid and different amines, followed by an acid- or base-mediated intramolecular cyclization. The use of threonine derivatives with glycolaldehyde in the Petasis reaction has been studied and successfully applied in the process, achieving morpholines with a higher fraction of sp3 carbon atoms compared to blockbuster drugs.

固体表面における協奏的触媒作用：金属錯体・金属カチオン・有機分子の集積による有機反応の促進

Bifunctional catalytic surface enables significant acceleration of organic reactions by concerted catalysis. For example, allylation of nucleophiles smoothly occurred on a SiO2 surface possessing both Pd complex and tertiary amine. In the case of the catalysts with Pd-bisphosphine complex and 1,4-diazabicyclo [2.2.2] octane (DABCO) on same SiO2 surface, the turnover number (TON) value based on Pd species approached up to 106000. Other reaction systems containing Rh complex and In cation for 1,4-addition of organoboronic acid and cyanation reaction of aldehyde, respectively, are also described. These SiO2- and SiO2-Al2O3-supported catalysts were characterized by several spectroscopic techniques, such as solid-state NMR, X-ray absorption fine structure (XAFS) spectroscopy, and X-ray photoelectron spectroscopy (XPS), for atomic or molecular-level understanding. Reaction mechanisms including acceleration process is also discussed based on several experiments.

Electrochemical Properties and Reactions of Organoboronic Acid Esters Containing Unsaturated Bonds at Their α-Position

Electrochemical analyses of 2-(cynnamyl)boronic acid pinacol ester and (3-phenyl-2-propynyl)boronic acid pinacol ester, and their trimethylsilyl analogues as well as their parent compounds were comparatively studied by cyclic voltammetry measurements. We found remarkable negative shifts of the oxidation potentials of the organoboronic acid pinacol esters in the presence of fluoride ions compared to those in the absence of fluoride ions. The negative shift observed was more pronounced than that of the corresponding trimethylsilyl compounds. Such marked negative shift seems to be derived from the formation of negatively charged boron-ate complex with fluoride ions as well as β-effect of organoborate. Anodic acetoxylation of organoboronic acid pinacol esters was achieved in NaOAc/AcOH, while their alkoxylation was successfully carried out in the presence of fluoride ions.

ChemInform Abstract: Nickel‐Catalyzed Cyclization of Alkyne‐Nitriles with Organoboronic Acids Involving anti‐Carbometalation of Alkynes.

A nickel-catalyzed regioselective addition/cyclization of o-(cyano)phenyl propargyl ethers with arylboronic acids has been developed, which provides an efficient protocol for the synthesis of highly functionalized 1-naphthylamines with wide structural diversity. The reaction is characterized by a regioselective and anti-addition of the arylboronic acids to the alkyne and subsequent facile nucleophilic addition of the resulting alkenylmetal to the tethered cyano group. Mechanistic studies reveal that a Ni(I) species might be involved in the catalytic process.

Dioxygen-Promoted Pd-Catalyzed Aminocarbonylation of Organoboronic Acids with Amines and CO: A Direct Approach to Tertiary Amides.

A direct approach from organoboronic acids and amines to tertiary amides via Pd-catalyzed aerobic aminocarbonylation has been developed. The presence of O2 significantly promotes the efficiency of this transformation. This method uses commercially available organoboronic acids and cheap CO and O2 (1 atm), which renders amides an easy synthesis with broad substrate scope and high functional group tolerance.

Synthesis of New Chiral Benzimidazolylidene–Rh Complexes and Their Application in Asymmetric Addition Reactions of Organoboronic Acids to Aldehydes

A series of novel chiral N-heterocyclic carbene rhodium complexes (NHC–Rh) based on benzimidazole have been prepared, and all of the NHC–Rh complexes were fully characterized by NMR and mass spectrometry. These complexes could be used as catalysts for the asymmetric 1,2-addition of organoboronic acids to aldehydes, affording chiral diarylmethanols with high yields and moderate enantioselectivities.

Bio‐Waste Corn–cob Cellulose Supported Poly(amidoxime) Palladium Nanoparticles for Suzuki‐Miyaura Cross‐Coupling Reactions

AbstractWaste corn‐cob cellulose supported poly(amidoxime) palladium nanoparticles (PdNs@PA) were prepared by the surface modification of waste corn‐cob cellulose through graft co‐polymerization and subsequent amidoximation. The supported nanoperticles showed high catalytic activity (45‐400 mol ppm) towards Suzuki‐Miyaura cross‐coupling of aryl bromides/chlorides with organoboronic acids to give the corresponding biaryl products up to 99 % yield with high turnover number (TON) 19777 and turnover frequency (TOF) 4944 h−1. The PdNs@PA was easily recovered from the reaction mixture and reused several times without significant loss of its catalytic activity.

Electrochemical Properties and Reactions of Organoboronic Acids in the Presence of Fluoride Ions

AbstractElectrochemical analyses of alkyl, phenyl, and thienylboronic acids were comparatively studied by cyclic voltammetric measurements in the absence and presence of fluoride ions, and we found remarkable negative shift of their oxidation potentials in the presence of fluoride ions compared with those in the absence of fluoride ions. Such negative shift seems to be derived from the formation of negative charged boron‐ate complex with fluoride ions. Anodic fluorination of 2‐acetyl‐5‐thienylboronic acid was carried out to provide mono‐ and trifluoro products eliminating a boryl group in moderate yields. These results clearly indicate that a boryl group with fluoride ions is a good electroauxiliary.

Nickel‐Catalyzed Desulfitative C–C Cross Coupling: The Synthesis of 6‐Aza‐Tetrahydroquinazolines and their Solvatochromism

AbstractA convenient nickel catalyzed approach towards the synthesis of diversely substituted 6‐aza‐tetrahydroquinazolines from pyrido‐pyrimidine‐2‐thione motifs with organo boronic acids by non‐basic desulfitative C−C cross coupling strategy is described. The absorption and emission spectral studies on some of the synthesised compounds reveal the existent of D‐π‐A−D systems displaying solvatochromism.

Copper(II)‐Catalyzed C–S Cross‐Coupling with Thiazolidine‐2‐thiones and Boronic Acids: Synthesis of Azole Sulfides

AbstractThe copper(II)‐catalyzed C–S cross coupling of thiazolidine‐2‐thiones with organoboronic acids towards the synthesis of azole sulfides was investigated. This mild and base‐free protocol has the advantages of short reaction times and excellent yields with no need for an ancillary ligand.

ChemInform Abstract: Supported Palladium Nanoparticle‐Catalyzed Carboxylation of Aryl Halides, Alkenylsilanes, and Organoboronic Acids Employing Oxalic Acid as the C1 Source.

Polystyrene-supported palladium(0) (Pd@PS) nanoparticles as a heterogeneous catalyst have been developed for caboxylation of aryl halides, alkenylsilanes, and organoboronic acids to produce the corresponding carboxylic acids with minor quantities of corresponding aldehydes using bench-stable and inexpensive oxalic acid as the C1 source under focused microwave irradiation. The close vicinity of oxalic acid to Pd@PS maintained through ionic bonding helped to produce CO2 over the catalytic surface that concurrently participated in the carboxylation reaction.

α‐Phosphonovinyl Arylsulfonates: An Attractive Partner for the Synthesis of α‐Substituted Vinylphosphonates through Palladium‐Catalyzed Suzuki Reactions

AbstractIt has been demonstrated that a variety of α‐phosphonovinyl arylsulfonates with electron‐neutral, ‐donating, and ‐withdrawing groups on the phenyl ring could be conveniently and efficiently prepared. In the presence of a Pd(OAc)2/SPhos‐based catalyst, various organoboron compounds could be employed as the nucleophilic coupling partners, such as organoboronic acids, boronate esters, and organotrifluoroborates. The newly developed O‐centered electrophiles could couple with a multitude of aryl, heteroaryl, and alkylboron reagents, to give α‐substituted vinylphosphonates in moderate to excellent yields. Generally, the Suzuki reaction is tolerant of extensive substitution at the aromatic ring of both electrophilic and nucleophilic coupling partners. As in the case of the Suzuki reaction of 8‐quinolineboronic acid, proper choice of α‐phosphonovinyl arylsulfonates is critical to efficient coupling. Moreover, the prospect for application of this method to complex synthesis has been demonstrated through the coupling of estrone‐derived arylborons. The present protocol also features mild conditions and high efficiency.

ChemInform Abstract: An Efficient Method for the Synthesis of 2‐Methylallyl Alkenes by Cross‐Coupling Reactions.

To obtain aromatic 2-methylallyl derivatives, cross-coupling reactions between 2-methyl-2-propen-1-ol and various boronic acids were studied. Among allylic alcohols described for such cross-coupling reactions, 2-methyl-2-propen-1-ol has a low reactivity. Indeed, this substrate did not react with several boronic acids under the previously described conditions and new reaction conditions were investigated. We describe herein a new protocol with small amounts of palladium and ligand, without any additive solvent and under microwave heating. A subsequent simple distillation process not only leads to the product, but also allows the ‘reagent–solvent’ to be recycled for further cross-coupling reactions, without loss of yield. Scope and limitations were studied. Furthermore, when this easy cross-coupling reaction was extended to a wide range of organoboronic acids, high functional group tolerance was observed and a new series of alkenes was synthesized in good yields.

ChemInform Abstract: Copper‐Catalyzed Cyanation of Aryl‐ and Alkenylboronic Reagents with Cyanogen Iodide.

Direct catalytic cyanation of organoboronic acids with cyanogen iodide has been achieved by using a copper–bipyridine catalyst system. The cyanation reaction is likely to occur through two catalytic cycles: copper(II)-catalyzed iodination of organoboronic acids and the following cyanidocopper(I)-mediated cyanation of organic iodides.