Boronic acid, phenyl

C13H11NS2 7643-08-5) see Mesoridazine Thioridazine lV-(3-methylthiophenyl)anthranilic acid (CJ4H13NO2S 18902-93-7) see Thioridazine [4-(methylthio)phenyl]boronic acid (C7H,B02S 98546-51-1) see Rofecoxib 4-[4-(methylthio)phenyl]-2(5H)-furanone (CiiH, 02S 162012-28-4) see Rofecoxib... 

Phenyl boronic acid synthesis (Clariant/Frankfurt) [10]... 

Temperature profile of the phenyl boronic acid synthesis along the major steps of the process flow scheme. The difference in the temperatures of the conventional batch and the microreactor processes stand for the reduction in energy consumption and respective heat-transfer equipment when using the latter [10]... 

The asymmetric 1,4-conjugate addition of phenyl boronic acids to cyclohex-2-enone was catalysed by the Pd complex 141 (Fig. 2.25). Good to excellent yields and high ee (90-97%) were obtained under mild conditions and low catalyst loadings (rt, 3 mol%)... 

Fig. 2.25 Palladium catalysts and postulated intermediates in the asymmetric conjugate addition of phenyl boronic acids to cyclohex-2-enone...

Crude chloroform-methanol-water (30 60 8, v/v) extracts of immunostainedTLC bands were analyzed without further purification by nanoelectrospray low-energy mass spectrometry. The authors showed that this effective PLC/MS-joined procedure offers a wide range of applications for any carbohydrate-binding agents such as bacterial toxins, plant lectins, and others. Phenyl-boronic acid (PBA) immobilized on stationary support phases can be put to similar applications. This technology, named boronate affinity chromatography (BAC), consists of a chemical reaction of 1,2- and 1,3-diols with the bonded-phase PBA to form a stable... 

The Baccatin III synthesis by K. C. Nicolaou and co-workers is summarized in Scheme 13.54. Diels-Alder reactions are prominent in forming the early intermediates. In Step A the pyrone ring served as the diene. This reaction was facilitated by phenyl-boronic acid, which brings the diene and dienophile together as a boronate, permitting an intramolecular reaction. 

Krische and coworkers [44] developed a Rh-catalyzed asymmetric domino Michael/aldol reaction for the synthesis of substituted cyclopentanols and cyclohex-anols. In this process, three contiguous stereogenic centers, including a quaternary center, are formed with excellent diastereo- and enantioselectivity. Thus, using an enantiopure Rh-BINAP catalyst system and phenyl boronic acid, substrates 2-108 are converted into the correspondding cyclized products 2-109 in 69-88% yield and with 94 and 95% ee, respectively (Scheme 2.24). 

Ternary Pd-catalyzed coupling reactions of bicyclic olefins (most often norbor-nadiene is used) with aryl and vinyl halides and various nucleophiles have been investigated intensively over the past few years [44]. A new approach in this field is to combine Heck and Suzuki reactions using a mixture of phenyliodide, phenyl-boronic acid and the norbornadiene dicarboxylate. Optimizing the conditions led to 84% of the desired biphenylnorbornene dicarboxylate [45]. Substituted phenyl-iodides and phenylboronic acids can also be used, though the variation at the norbornadiene moiety is highly limited. 

Typically, the boronic acid group is part of an aminophenyl boronic acid derivative, and this group has been used for bioconjugation and affinity chromatography purposes (Burnett et al., 1980 O Shannessy and Quarles, 1987). A common partner for a phenyl boronic acid group in bioconjugation is the salicylhydroxamic acid (SHA) group (Chapter 17, Section 3) (Reaction 59). 

In a more recent study, Wang and coworkers have discussed microwave-assisted Suzuki couplings employing a reusable polymer-supported palladium complex [141]. The supported catalyst was prepared from commercial Merrifield polystyrene resin under ultrasound Bonification. In a typical procedure for biaryl synthesis, 1 mmol of the requisite aryl bromide together with 1.1 equivalents of the phenyl-boronic acid, 2.5 equivalents of potassium carbonate, and 10 mg of the polystyrene-... 

The first microwave-promoted Suzuki couplings were reported in 1996 (Eq. 11.20) [17]. Phenyl boronic acid was coupled with 4-bromotoluene to give a fair yield of product after a reaction time of less than 3 min under single-mode irradiation. The same reaction had previously been conducted with a reported reaction time of 4 h. 

Equation 11.20 Suzuki coupling of phenyl boronic acid with 4-bromotoluene. 

Application of the complexes 63 in the Mizoroki-Heck reaction did not reveal higher activity than the previously examined palladium(II) complexes. However, in the Suzuki-Miyaura reaction, a drastically increased activity was observed with complex 63. Catalysis starts without a measurable induction period at mild temperatures accompanied by an extraordinarily high turnover frequency (TOF) of 552 [mol product x mol Pd x h ] at the start of the reaction for the coupling of p-chlorotoluene and phenyl boronic acid [Eq. (48)]. ... 

Solid czs-1,2-diols and pyrocatechols react quantitatively with phenyl-boronic acid to form the phenylboronic esters upon stoichiometric milling. The water of reaction is taken up by the crystals and can be removed in a vacuum [90]. Thus, the aliphatic diols 186 and 189 give the borolic esters 188 and 190 with 100% yield (Scheme 25). Equally successful is the reaction of pyrocatechol (191) and 187. The reaction mixture is heated to 80 °C after milling at 0 °C. 

There are several different routes to carboxamides. In most of these reactions, a carboxylic acid is converted to a more reactive intermediate, e.g. the acid chloride, which is then allowed to react with an amine. For practical reasons, it is preferable to form the reactive intermediate in situ. Arylboronic acids with electron-withdrawing groups such as (3,4,5-trifluorophenyl)boronic acid act as highly efficient catalysts in the amidation between carboxylic acids and amines. (3-Nitrophenyl)boronic acid and [3,5-bis(trifluoromethyl)phenyl]boronic acid are also effective eimidation catalysts and commercially available. 

The proposed mechanism of the boron-catalyzed amidation is depicted in the Figure. It has been ascertained by H NMR analysis that monoacyloxyboronic add 1 is produced by heating the 2 1 mixture of 4-phenylbutyric add and [3,5-bis(trifluoromethyl)phenyl]boronic acid in toluene under reflux with removal of water. The corresponding diacyloxyboron derivative is not observed at all. When 1 equiv of benzylamine is added to a solution of 1 in toluene, the amidation proceeds even at room temperature, but the reaction stops before 50% conversion because of hydrolysis of 1. These experimental results suggest that the rate-determining step is the generation of 1. 

A flask was charged with 4-bromo-iodobenzene (0.079 mol), 4-methoxy-2-methyl-phenyl boronic acid (0.087 mol), palladium acetate (0.004 mol), and triphenyl phosphine (0.008 mol) and then treated with 200 ml acetone and 250 ml 2M NaHCO i. The mixture was refluxed at 65°C for 18 hours and was then treated with water and diethyl ether and the organic layer isolated. This layer was washed with 40 ml saturated sodium chloride solution and water, dried over MgSC>4, filtered, and concentrated. The residue was purified by column chromatography using silica gel with CH2C12/ hexane, 1 1, and then recrystallized in / , 7 3, respectively, and 16.4 g of product isolated. 

A reactor containing 10 ml of toluene and 10 ml of aqueous Na2C03 was treated with the step 2 product (1.0 mmol), 2,7-dipinacol boron-9,9-di-octyl-fluoiene (1.0 mmol), tetrakis triphenylphosphine palladium (0.01 mmol), and 0.16 ml of tricaprylmethyl-ammonium chloride. The mixture was then treated with a few drops of bromobenzene and then refluxed for 1 hour and treated with a few drop of phenyl boronic acid and then further refluxed 15 hours and cooled. The mixture was diluted with toluene and isolated toluene layer washed with water. The mixture was filtered after adding 40 mg of the palladium scavenger 3-mercaptopropyl modified silica gel. The solution was then poured into methanol and a yellow polymer isolated. The polymer was redissolved in toluene and then purified using a short column of silica gel. The solution was rewashed with water, reprecipitated in ethanol, and 0.80 g of polymer isolated having an Mn of 32,800 Da. 

In a similar way, dinitro-4-azaheptane-l,7-diols reacted with phenyl-boronic acid to yield isomeric cis- and trans-substituted diptychs with condensed 5-nitrotetrahydro-2,l,3-boraoxazine rings (5)38,37 [Eq. (2)]. 

Wulff and his collaborators reported, in 1989, the preparation of imprinted polymers able to perform enantioselective synthesis [11, 12]. The imprinting complex was prepared by reacting 3,4-di-hydroxy-phenyl-alanine methyl-ester (l-DOPA methyl ester) (16) with the 4-vinyl-salicylaldehyde (17) to form the corresponding Schiff s base (18), which was further reacted with the 4-vinyl-phenyl-boronic acid (19) to afford to the corresponding ester (20) (Scheme 4). The imprinting complex obtained was then polymerised and the template removed. The resulting polymers were incubated with sodium glycinate to allow formation... 

In 2001, Cammidge et al. [47] reported the preparation of an MIP for Suzuki cross-coupling between p-bromoanisole (68) and phenyl-boronic acid (69) to give the corresponding 4-methoxy-biphenyl (70). 

The benzene derivatives containing the fluorinated sulfone have been prepared either by nucleophilic substitution of the 4-fluorophenyl derivative (e.g. 1) or by starting with the appropriately substituted sodium thiophenoxide and reacting with perfluoroalkyl iodide follow by oxidation with either MCPBA or chromium oxide (12. li.) The biphenyl derivatives have been prepared by palladium catalyzed cross coupling chemistry of the 4-bromophenyl derivative (e.g. 2) with substituted phenyl boronic acid (yields 37-84%) (JLH, .). Compound 16 has been prepared by palladium catalyzed cross coupling of (4-bromophenyl)perfluorohexyl sulfone with vinyl anisole in 37 % yield (JJL). The vinyl sulfones, 7 and 9, have been prepared by condensation of CH3S02Rf (JJL) with the appropriate aldehyde (yields 70,and 73%) following a literature procedure (1 ). Yields were not optimized. 

Tschierske developed a variety of molecules containing a p-terphenyl unit as backbone equipped with two terminal decyloxy chains and laterally attached crown ethers of different sizes [51-53]. The synthesis was straightforward starting from methyl-2,5-dibromobenzoate 30 that was coupled with [4-(decyloxy)phenyl]boronic acid 31 in a subsequent Pd°-catalyzed Suzuki reaction. The 2-hydroxymethyl crown ethers 32 were attached in the last step (Scheme 18) to yield mesogenic 33. 

The same group developed an interesting intermolecular palladium-catalyzed alienation of aryliodide with N-tosyl o-iodoanilines with nucleophiles in combination with two palladium-coupling reactions [69]. In this reaction, the N-allyl(2-iodopalladium)aniline intermediate 52 underwent an intramolecular Heck reaction followed by a cross-coupling reaction with phenyl boronic acid to give the 3,3-disubstituted indoline 53 in 78% yield (Scheme 8.27). 

---