Pinacolone

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 participate in condensation reactions. The carbonyl group can undergo the usual reactions (hydrogenation, reductive amination, etc.). It is a Schedule 3 compound under the Chemical Weapons Convention 1993, due to being related to pinacolyl alcohol, which is used in the production of soman. It is also a controlled export in Australia Group member states.

Preparation

Most famously, at least in the classroom, pinacolone arises by the pinacol rearrangement, which occurs by protonation of pinacol (2,3-dimethylbutane-2,3-diol).

File:800px-Pinacol rearragement.png

Industrially pinacolone is made by the hydrolysis of 4,4,5-trimethyl-1,3-dioxane, which is the product of isoprene and formaldehyde via the Prins reaction. It also is generated by ketonization of pivalic acid and acetic acid or acetone over metal oxide catalysts. 3-Methylbutanal is a starting material for 2,3-dimethyl-2-butene, which in turn is converted to pinacolone. Pinacolone can also be produced from 2-methy-2-butanol when reacted with C5 alcohols.

Uses

Pinacolone is produced in large amounts for use in fungicides, herbicides, and pesticides. Some derivatives include:

• retrosynthetic analysis of vibunazole showed that it was derived from pinacolone.
• It is also used to prepare pinacidil, as well as naminidil.
• Stiripentol
• Tribuzone
• Pivaloylacetonitrile is used in the synthesis of Doramapimod.
• Triadimefon
• Diclobutrazole
• Paclobutrazol
• Valconazole
• Diethylstilbestrol pinacolone [18922-13-9].
• Some kind of Bisphenol A derivative also U.S. patent 4599463
• Thiofanox

See also

• Pinacol
• Pinacolyl alcohol
• Soman