Pinacolone: 2-Butanone, 3,3-dimethyl

Other Rea.ctlons, The anhydride of neopentanoic acid, neopentanoyl anhydride [1538-75-6] can be made by the reaction of neopentanoic acid with acetic anhydride (25). The reaction of neopentanoic acid with acetone using various catalysts, such as titanium dioxide (26) or 2irconium oxide (27), gives 3,3-dimethyl-2-butanone [75-97-8] commonly referred to as pinacolone. Other routes to pinacolone include the reaction of pivaloyl chloride [3282-30-2] with Grignard reagents (28) and the condensation of neopentanoic acid with acetic acid using a rare-earth oxide catalyst (29). Amides of neopentanoic acid can be prepared direcdy from the acid, from the acid chloride, or from esters, using primary or secondary amines. 

DimethyI-2 3-butanediol has the common name piiuicol. On heating with aqueous acid, pinacol rearranges to pinacolone, 3,3-dimethyl-2-butanone. Suggest a mechanism for this reaction. 

Pinacolone (3,3-dimethyl-2-butanone) adds to aldehydes in an enantioselective manner when advantage of the induction by a C 2-symmetric boron enolate derived by addition of (2/ ,5/ )-l-chloro-2,5-diphenylborolane is taken. In this way, /i-hydroxy ketones, whose absolute configuration is unknown, arc obtained with 32- 84% cc58. 

The reactions depicted in Fig. 32 are most often carried out at low temperatures. The incursion of a thermal process at elevated temperatures has occasionally been observed. In some cases the thermal oxygenation products are identical to the photochemical products and in other cases are different. For example, when 2,3-dimethyl-2-butene/02 NaY is warmed above — 20 °C a reaction was observed which led to pinacolone (3,3-dimethyl-2-butanone) as the major product.98,110 Pin-acolone is not formed in the photochemical reaction at the same temperature. On the other hand, identical products were observed in the thermal and photochemical intrazeolite oxygenations of cyclohexane.114,133 135 These intrazeolite thermal processes occur at temperatures well below that necessary to induce a classical autooxidation process in solution. Consequently, the strong electrostatic stabilization of oxygen CT complexes may also play a role in the thermal oxygenations. Indeed, the increase in reactivity of the thermal oxygenation of cyclohexane with increasing intrazeolite electrostatic field led to the conclusion that initiation of both the thermal and photochemically activated processes occur by the same CT mechanism.134 Identical kinetic isotope effects (kH/kD — 5.5+0.2) for the thermal and photochemical processes appears to support this conclusion.133... 

Material accountability (the sum of recovered chloropinacolone, methyl pivaloyl acetate, and pinacolone) with the active Pd monophosphine and carbene complexes was in the range of 92-99% without accounting for impurities present in the starting chloropinacolone. A GC-MS examination of several product mixtures was undertaken to see if there were any additional, unanticipated by-products. The only additional material identified was a-methoxy pinacolone (l-methoxy-3,3-dimethyl-2-butanone). This compound was formed by methanolysis of the starting a-chloropinacolone and appears to be formed by a mixture of catalyzed and uncatalyzed processes Since this product was not anticipated, it was not quantified but represents the majority of, if not the only, remaining volatile product. No attempt was made to determine the presence of any quaternary ammonium salt formed by similar alkylation of the amine base by a-chloropinacolone. 

Problem 17.46 Can 3,3-dimethyl-2-butanone (pinacolone), CHXOC(CH,), be synthesized from acetoacetic ester ... 

Pinacol rearrangement is a dehydration of a 1,2-diol to form a ketone. 2,3-drmethyl-2,3-butanediol has the common name pinacol (a symmetrical diol). When it is treated with strong acid, e.g. H2SO4, it gives 3,3-dimethyl-2-butanone (methyl r-butyl ketone), also commonly known as pinacolone. The product results from the loss of water and molecular rearrangement. In the rearrangement of pinacol equivalent carbocations are formed no matter which hydroxyl group is protonated and leaves. 

Seebach, Dunitz and coworkers reported, in 1981226, the first crystal structures of lithium enolates of simple ketones, obtained in THF from pinacolone (3,3-dimethyl-2-butanone) and cyclopentanone. Both were arranged as tetrasolvated cubic tetramers, one THF molecule capping each lithium cation (Scheme 58A). Note that pinacolone enolate can also be crystallized, from heptane at — 20 °C, as a prismatic unsolvated hexamer exhibiting an approximate S6 symmetry and six slight it-cation interactions227,228 (Scheme 58B) or as a dimer in the presence of 2 molecules of TriMEDA29. Similarly,... 

Dimethyl-2,3-butanediol (pinacol) (2.12) on treatment with H2SO4 generates 3,3-dimethyl-2-butanone, commonly known as pinacolone (2.13). Pinacol itself is produced by magnesium reduction of acetone, probably by way of a ketyl intermediate. 

In 1961, kinetic studies of methylmagnesium bromide with benzophenone and pinacolone, 3,3-dimethyl-2-butanone [37], confirmed the existing opinion at that time [see Ref. 38, for its origin]. First, a complex was formed between the Grignard reagent and the ketone. The complex was then attacked by a second Grignard molecule to form the addition product (Scheme 7) ... 

Seebach, Dunitz and cowoikers fust described the THF-solvated tetrameric aggregates obtained from THF solutions of 3,3-dimethyl-2-butanone (pinacolone) and cyclopentanone lithium enolates. These are represented as (137). The pinacolone enolate also crystallizes as the unsolvated hexamer (138) from hydrocarbon solution, but this hexamer rearranges instantaneously to the tetramer (137) in the presence of THF. Williard and Carpenter completed the characterization of both the Na+ and the K+ pinacolone enolates.Quite unexpectedly the Na pinacolone enolate is obtained from hydrocarbon/THF solutions as the tetramer (139) with solvation of the Na atoms by unenolized ketone instead of by THF. Hie potassium pinacolone enolate is a hexameric THF solvate depicted as (140) and described as a hexagonal prism. A molecular model of (140) reveals slight chair-like distortions of the hexagonal faces in (140) so that the solvating THF molecules nicely fit into the holes between the pinacolone residues. 

Synthesis of the morpholine enamine from pinacolone (3,3-dimethyl-2-butanone) by the modified TiC -method discussed above was complicated by considerable self-condensation of the ketone. 

The catalysts were pre-activated before use at 450 °C. The olefin 2,3-dimethyl-2-butene (purchased from ACROS, 95%) was distilled before use. H2O2 (30 wt% aqueous) was purchased from Merck, l,3,5-tri-/e/-/-butylbenzeen from Fluka (>97%), pinacol (2,3-dimethyl-2,3-butanediol) from Aldrich (98%), pinacolone (3,3-dimethyl-2-butanone) from ACROS... 

The pinacol rearrangement was first described by Fittig in 1860 [10]-treatment of pinacol (2,3-dimethyl-2,3-butanediol, 1), a ditertiary 1,2-diol, with sulfuric acid resulted in the formation of pinacolone (3,3-dimethyl-2-butanone, 2) (Scheme 1). The overall reaction is dehydration with concomitant migration of a methyl substituent. 

D.18) 2-Butanone, 3,3-dimethyl-, 3,3-dimethylbutan-2-one, tert-butyl methyl ketone, 2,2-dimethylbutanone, trimethylacetone, pinacoline, pinacolone 75-97-8]... 

Some years later, ligandless conditions were tilso used by Prashad and coworkers [25]. An efficient large-scale synthesis of l-(4-chlorophenyl)-3,3-dimethyl-2-butanone by arylation of pinacolone with l-bromo-4-chlorobenzene in the presence of Pd(OAc)2 and NaOfBu in toluene was described. An increase in the concentration of NaOfBu to 2.5-3.0 equiv suppressed the formation of over-arylated products. The yield of the l-(4-chlorophenyl)-3,3-dimethyl-2-butanone was very similar when ligandless conditions were applied [25]. 

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