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Examples of boronic esters Boronic ester Diol Structural formula Molar mass CAS number Boiling point (°C) Allylboronic acid pinacol ester: pinacol: 168.04: 72824-04-5: 50–53 (5 mmHg) Phenyl boronic acid trimethylene glycol ester: trimethylene glycol: 161.99: 4406-77-3: 106 (2 mm Hg) Diisopropoxymethylborane: isopropanol: 144.02 86595-27-9: ...
Phenylboronic acid or benzeneboronic acid, abbreviated as PhB(OH) 2 where Ph is the phenyl group C 6 H 5 - and B(OH) 2 is a boronic acid containing a phenyl substituent and two hydroxyl groups attached to boron. Phenylboronic acid is a white powder and is commonly used in organic synthesis.
In fact, the addition of acid (H+) or hydroxide (OH-) acts to attenuate protodeboronation by shifting the speciation away from the reactive zwitterion. It is important to note that not all basic heteroaromatic boronic acids are reactive through a zwitterionic intermediate. Scheme for the speciation of 2-pyridine boronic acid in aqueous solution
Pinacol is a branched alcohol which finds use in organic syntheses. It is a diol that has hydroxyl groups on vicinal carbon atoms. A white solid that melts just above room temperature, pinacol is notable for undergoing the pinacol rearrangement in the presence of acid and for being the namesake of the pinacol coupling reaction .
Boronic acids and esters are classified depending on the type of carbon group (R) directly bonded to boron, for example alkyl-, alkenyl-, alkynyl-, and aryl-boronic esters. The most common type of starting materials that incorporate boronic esters into organic compounds for transition metal catalyzed borylation reactions have the general ...
It has the formula [(CH 3) 4 C 2 O 2 B] 2; the pinacol groups are sometimes abbreviated as "pin", so the structure is sometimes represented as B 2 pin 2. It is a colourless solid that is soluble in organic solvents. It is a commercially available reagent for making pinacol boronic esters for organic synthesis.
The reaction is named after pinacol (also known as 2,3-dimethyl-2,3-butanediol or tetramethylethylene glycol), which is the product of this reaction when done with acetone as reagent. The reaction is usually a homocoupling but intramolecular cross-coupling reactions are also possible. Pinacol was discovered by Wilhelm Rudolph Fittig in 1859.
The reactants are the lactol derived from L-phenyl-lactic acid and acetone, l-phenylalanine methyl ester and a boronic acid. The reaction takes place in ethanol at room temperature to give the product, an anti-1,2-amino alcohol with a high diastereomeric excess. [34] Petasis reaction example (Kumagai et al.)
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