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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.
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.
Pinacolyl alcohol (also known as 3,3-dimethylbutan-2-ol and as pine alcohol) is one of the isomeric hexanols and a secondary alcohol. Pinacolyl alcohol appears on the List of Schedule 2 substances of the Chemical Weapons Convention as a precursor for the nerve agent soman .
A Mukaiyama aldol addition (magnesium bromide / toluene) took place between aldehyde 7 and ketene silyl acetal 8 with 71% stereoselectivity to alcohol 9 which was protected as the TBS ether 10 (TBSOTf, 2,6-lutidine). The ester group was reduced with DIBAL to an alcohol and then back oxidized to aldehyde 11 by Swern oxidation.
The reaction product he obtained instead he called paraceton which he believed to be an acetone dimer. In his second publication in 1860 he reacted paraceton with sulfuric acid (the actual pinacol rearrangement). Again Fittig was unable to assign a molecular structure to the reaction product which he assumed to be another isomer or a polymer.
The B-B bond adds across alkenes and alkynes to give the 1,2-diborylated alkanes and alkenes. Using various organorhodium or organoiridium catalysts, it can also be installed onto saturated hydrocarbons: [3] CH 3 (CH 2) 6 CH 3 + [pinB] 2 → pinBH + CH 3 (CH 2) 7 Bpin. These reactions proceed via boryl complexes. Bis(pinacolato)diboron can also ...
Pinacolone (3,3-dimethyl-2-butanone) is an important ketone in organic chemistry. It is a colorless liquid with a slight peppermint or camphor odor. It is a precursor to triazolylpinacolone in the synthesis of the fungicide triadimefon and in synthesis of the herbicide metribuzin. The molecule is an unsymmetrical ketone. The α-methyl group can ...
The bottom part of ring B was constructed by nucleophilic addition to the aldehyde of 2.1 (scheme 2) with dibenzyl acetal of 2-bromobenzaldehyde 2.2 as its aryllithium.This step is much in common with the B ring synthesis in the Nicolaou Taxol total synthesis except that the aldehyde group is located at ring A and not ring B.