Phenyl-boron

A polymeric version of the phenyl boronate has been developed. 

Ethyl Boronate, 243 Phenyl Boronate, 244 o-Acetamidophenyl Boronate, 244... 

PhB(OH)2, PhH or Pyr. A polymeric version of the phenyl boronate has been developed.Phenyl boronates are stable to the conditions of stannyla-tion and have been used for selective sulfation to produce monosulfated monosaccharides. Phenyl boronates were found to be stable to oxidation with pcc ... 

Propanediol, acetone. This method removes the boronate by exchange. 2-Methylpentane-2,5-diol in acetic acid cleaves a phenyl boronate (85% yield). 

This boronate was developed to confer added stability toward hydrolysis. It was shown to be substantially more stable to hydrolysis than the simple phenyl boronate because of coordination of the the ortho acetamide to the boronate. ... 

Syntheses of 6-Deoxy-2- and 3-O-methyl-D-allose and Some 6-Deoxyhexopyranoside Phenyl-boronates," J. S. Brimacombe, A. Husain, F. Hunedy, and M. Stacey, Adv. Chem. Sen, No 74 ( Deoxy-sugars") (1968) 56 - 69. 

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]... 

Reaction of ally I tetraacetyl P-D-glucopyranoside and phenyl boronic... 

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. 

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