2- Formylphenylboronic acid

Yeste et al.7 have developed chiral derivatization protocols for determination of enantiopurity of chiral diols by the H and 19F NMR spectroscopy. Three-component method has required the treatment of diol with 2-formylphenylboronic acid and a-methyl-4-fluorobenzylamine [4],... 

Ir(OH)(cod)]2 catalyzed a formal [3+2] cycloaddition of 2-formylphenylboronic acid and 1,3-dienes (Scheme 11.41) [50]. The transmetaUation of boronic acid with iridium would yield aryliridium, where the carbonyl group coordinates to the metal. An electrophihc attack of the diene terminus to formyl carbon would then... 

Boranes and, to a lesser extent, boronic acids can undergo slow hydrolysis (protode-boration) in the presence of protic solvents. This unwanted reaction can become predominant if a cross-coupling reaction only proceeds slowly (e.g. with electron-rich, sterically demanding, or unreactive halides Scheme 8.20 see also Scheme 8.14) or if the boron derivative is particularly sensitive, for example 2-formylphenylboronic acid. In such instances the reaction should be performed under anhydrous conditions in an aprotic solvent with a boronic acid ester [151] or a stannane. 

Formylphenylboronic acid (l.Oequiv, 1.93 g, 12.9 mmol) was suspended in 50 mL benzene in a 100-mL round-bottomed flask with stir bar and pinacol (l.lequiv, 1.67g, 14.1 mmol) was added. A Dean-Stark trap (DST) was attached and filled with 15 mL benzene. The joints were sealed with Teflon tape and the mixture was vigorously refluxed (90 °C) with stirring under air until all the calculated amount of water present had collected within the DST (ca. 4—5 hours). After cooling to room temperature, the DST was drained and removed. Methyl (triphenylphosphoranylidene) acetate (1.3equiv, 5.6 g, 16.8 mmol) was then added in one portion, the round-bottomed flask was sealed with a rubber septum, and the mixture stirred at room temperature for 16 hours. 

MeCOjH catalysed the amination-reduction reaction of 2-formylphenylboronic acid used in excess, with Af-aUcylaniline and NaBH(OAc)3 as the reducing agent to form 2-[(iV-alkylanilmo) methyl]phenylboronic acid with up to 66% yield. The crystal stmc-ture of the aromatic amine derivative was determined. ... 

The set of 2-thiocarbamoylated 2,3,1-benzodiazaborines 148a—h, synthesized from 2-formylphenylboronic acids and thiosemicarbazides, was sought for potential antifungal activity (Scheme 52) (2015AJC366). Of the eight compounds prepared, four showed at least some activity against... 

Scheme 2.6 Reaction of 1,2-aminoalcohols with 2-formylphenylboronic acid.

To study the interaction of phenylboronic acids with amines in water, Yatsimirsky et al. used NMR spectroscopy to probe the charged state of the boron when complexing with an amine. At neutral pH ( 7.0), 2-formylphenylboronic acid (2-FPBA) shows two boron resonances at 29.3 and 8.6 ppm. Acidification of the solution to pH 6.5 results in the complete disappearance of the 8.6 ppm peak. Hence, the peak at 29.3 ppm corresponds to the neutral boronic acid FPBA. Increasing the pH of the solution to pH 9.0 shows elimination of the 29.3 ppm signal. This means that the peak at 8.6 ppm corresponds to the anionic boron in 17 (Scheme 2.9). To deduce... 

The protocol is based on the assembly of 2-formylphenylboronic acid and enantiopure a-methylbenzylamine to afford a mixture of diastereoisomeric iminoboronate esters whose ratio is an accurate reflection of the enantiopurity of the parent diol (Scheme 6.2 and Figure 6.22). The enantiomeric excess can be easily determined using NMR (Figure 6.22). The e.e. values of various diols can be determined using this protocol. 

It is challenging to determine the e.e. value of simple chiral hydrox-ylamines because there is only one binding site. However, based on the B-N interaction, the e.e. value of simple amines can also be determined by using H NMR analysis based on the three-component assembly of 2-formylphenylboronic acid, racemic BINOL and the chiral hydroxyl-amines to afford a mixture of diastereomeric nitrono-boronate esters whose ratio is an accurate reflection of the enantiopurity of the parent hydroxylamine (Scheme 6.3). ... 

Suzuki coupling reactions of 12 and 13 with 2-formylphenylboronic acid afforded the corresponding biaryl products, which were cyclized with ammonia to yield hitherto undescribed pyridazino[4,5-c]isoquinolinones (Equations 28 and 29) [30],... 

SCHEME 50.1. Borate-imine complex formed by the reaction of a diol, 2-formylphenylboronic acid, and 1-phenylethylamine. 

Also the ring-chain tautomerism of 2-formylphenylboronic acids 5 (Scheme 5.3) was studied by variable-temperature NMR spectroscopy to determine the equilibrium constants as well as enthalpies and entropies of tautomerization in a mixed solvent (acetone-dg/D20 = 95 5) [17]. 

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