Phenyl boronic add

There are several different routes to carboxamides.3 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.4 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.5 (3-Nitrophenyl)boronic add and [3,5-bis(triffuoromethyl)phenyl]boronic add are also effective amidation catalysts and commercially available. 

In a further example, phenyl boronic add-functionalized CdSe/ZnS QDs were used to bind NADor NADH via the boronic acid ligand to form boronate esters. The quenching of the QDs luminescence by the NAD + cofactor, via an ET quenching route, was substantially more efficient than was the quenching of QDs by NADH. This difference in quenching between NAD and NADH enabled QDs to be used for the luminescence analysis of NAD -dependent enzymes and their substrates, such as the AlcDH/ethanol system [141] (Figure 6.31a). The biocatalytic reduction of the... 

B, Werner, Selectivity gains and energy savings for the industrial phenyl boronic add process using micromixer/tuhular reactors, Org. Process Res. Dev. 2004, 8,511. 

Figure 9.3 Temperature profile of the phenyl boronic add synthesis along the major steps of the process flow scheme (AT ambient temperature THF tetrahydrofuran). The difference in 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 (by courtesy of ACS) [23].

Coupling partner RY E-1 -hexenyl boronic add or phenyl boronic add (1.1 equiv) Additives 2 equiv NaOEt or KOH Conditions dioxane or benzene, 80 °C... 

The boronic acid (or phenyl boronic adds) derivatives can be introduced onto particles surface via various processes starting from simple chemical grafting onto preformed reactive magnetic particles to direct incorporation into the used recipes for particle elaboration. 

Arylboron Formation Investigated in Micro Reactors Organic synthesis 40 [OS 40] Formation of phenyl esters of boronic add... 

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. 

Two further methods of preparing organoboron compounds have been the subject of fairly recent detailed study, namely, reaction of boron halides with hydrocarbons and addition of boron hydrides to olefins. For instance, arylboron dihalides are formed when boron trihalides are heated with aromatic hydrocarbons, aluminum chloride, and aluminum powder,217 and phenyl-boron dibromide has been prepared analogously.218 Further, boron halides such as diboron tetrachloride and tetrafluoride add to olefins, yielding bis-(dichloroboryl) and bis(difluoroboryl) compounds 219... 

El-Sayed and co-workers more recently reported on the catalytic activity of PVP-stabUized aqueous palladium colloids in Suzuki reactions (substrates 2-iodo-thiophene or phenyl iodide and 2-thiophene boronic add or phenylboronic acid 0.3 mol% palladium 12 h reflux) (Table 1) [20]. They did not find such a clear... 

The use of expensive and unstable ZnPli2 in the preparation of chiral di-arylmethanol derivatives, with electronically and sterically similar aryl rings, made this approach less attractive for the enantioselective synthesis. In order to avoid this inconvenience, other alternative preparations of arylzinc reagents were evaluated.As a first choice, Yus et al. proposed the use of arylboronic adds as a viable source of phenyl (Scheme 4.19). Thus, the reaction of various boronic acids with an excess of ZnEt2 at 70 °C gave the corresponding arylzinc intermediates (probably aryl(ethyl)zincs), which were trapped by reaction with dif-... 

Electron-rich aromatic compounds, such as phenol, anisole and A,./V-dimethylaniline, add to bis(2-trichloroethyl) azodicarboxylate under the influence of lithium perchlorate, boron trifluoride etherate or zinc chloride to yield para-substituted products 74, which are transformed into the anilines 75 by means of zinc and acetic acid86. Triflic acid (trifluoromethanesulphonic acid) catalyses the reactions of phenyl azide with benzene, toluene, chlorobenzene and naphthalene, to give TV-arylanilines (equation 34)87. 

A wide variety of substituted boronates are available commercially. For phenyl supports, use a phenyl or biphenyl (napthalene) derivative. For nonphenyl supports, evaluate both weakly and strongly hydrophobic alkyl derivatives (straight chain or branched). Raise sample pH to at least 8 and add the boronate derivative of choice to a concentration of at least 1 mM. The sample need not be buffer-exchanged prior to injection. Column buffers should be at least pH 8. 

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