Ketone pinacolone

A reaction that follows this pattern is the acid-catalyzed conversion of diols to ketones, which is known as the pinacol rearrangement.60 The classic example of this reaction is the conversion of 2,3-dimethylbutane-2,3-diol(pinacol) to methyl /-butyl ketone (pinacolone).61... 

Yamamoto has recently described a novel catalytic, asymmetric aldol addition reaction of enol stannanes 19 and 21 with aldehydes (Eqs. 8B2.6 and 8B2.7) [14]. The stannyl ketones are prepared solvent-free by treatment of the corresponding enol acetates with tributyltin methoxide. Although, in general, these enolates are known to exist as mixtures of C- and 0-bound tautomers, it is reported that the mixture may be utilized in the catalytic process. The complexes Yamamoto utilized in this unprecedented process are noteworthy in their novelty as catalysts for catalytic C-C bond-forming reactions. The active complex is generated upon treatment of Ag(OTf) with (R)-BINAP in THF. Under optimal conditions, 10 mol % catalyst 20 effects the addition of enol stannanes with benzaldehyde, hydrocinnamaldehyde, or cinnamaldehyde to give the adducts of acetone, rerf-butyl methyl ketone (pinacolone), and acetophenone in good yields and 41-95% ee (Table 8B2.3). 

The dehydration of ditertiary alcohols in the presence of hydrobromic acid may lead to dienes (e.g. pinacol to 2,3-dimethylbuta- 1,3-diene, cognate preparation in Expt 5.12), although in this case some concomitant rearrangement to t-butyl methyl ketone (pinacolone, Expt 5.98) occurs under the acidic conditions employed. 

The conversion of pinacol (Expt 5.35) to t-butyl methyl ketone (pinacolone, Expt 5.98) under acid conditions exemplifies a general reaction of 1,2-diols (the pinacol-pinacolone rearrangement). The mechanism, formulated below, involves loss of water from the protonated 1,2-diol accompanied by a 1,2-nucleophilic shift of a methyl group. 

The pinacol rearrangement is a useful reaction that proceeds via a carbocation rearrangement. Treatment of 2,3-dimethyl-2,3-butanediol, also known as pinacol, with acid results in the formation of a ketone, pinacolone ... 

Experiment 5.98 t-BUTYL METHYL KETONE (Pinacolone) Me2C(OH)-C(OH)Me2 Me-CO-CMe3... 

Deviations from the Bronsted lines were observed for iodination of several ketones (acetone, diethyl ketone, isopropyl methyl ketone, pinacolone and cyclohexanone) (Feather and Gold, 1965) and for dedeuteration of [2-2H] isobutyraldehyde (Hine et al., 1965) when these reactions are catalysed by pyridines with one or two methyl substituents in the 2- and 6-position. They were ascribed to steric hindrance since their magnitude depends on the structure of the ketone (the deviations increase along the series from acetone to isopropyl methyl ketone to pinacolone) and on the number of a- methyl substituents in the base. It was at first suggested that such steric effects favour a tram coplanar arrangement of the C=0 bond and of the C(a)—H bond at the... 

The number of publications describing new ligands that allow the transfer hydrogenation of aromatic ketones with over 90 % ee has grown in leaps and bounds since 1996 [15]. In these reactions the use of ruthenium [15a-f] and iridium [15g] as the catalytically active metals has recently been augmented by the use of phosphorus-free ligands such as chiral diamines, amino alcohols, and bisthioureas such as 7 [15a,e-g]. A ruthenium-catalyzed transfer hydrogenation with 92 % ee has even been reported for the aliphatic ketone pinacolone (tert-butyl methyl ketone) [16]. 

Strong CIDNP effects may be observed during photolysis of dialkyl ketones and an example will be treated in this Section. Fig, 8a shows an NMR spectrum taken during irradiation of a 0.7 M solution of tert.-butyl methyl ketone (pinacolone) in benzene with the unfiltered light of a high pressure mercury lamp 3). When compared with the spectrum taken after 20 minutes ir-... 

Inconclusive results were obtained for reactive species in solution (see Schemes 7 and 8 [37]). Indeed RMgBr was used in Scheme 8 in the reaction sequence that included a preliminary complexation of the ketone (pinacolone) with magnesium bromide. 

Exactly 10 years after the previous statement appeared, the first lithium enolate crystal structures were published as (5) and (6). Thus, structural information derived from X-ray diffraction analysis proved the tetrameric, cubic geometry for the THF-solvated, lithium enolates derived from r-butyl methyl ketone (pinacolone) and from cyclopentanone. Hence, the tetrameric aggregate characterized previously by NMR as (7) was now defined unambiguously. Moreover, the general tetrameric aggregate (7) now became embellished in (5) and (6) by the inclusion of coordinating solvent molecules, i.e. THE. A representative quotation from this 1981 crystal structure analysis is given below. 

Indanedione derivatives, i.e. the derivatives of 2-acyl-1,3-indanedione, are also compounds with anticoagulant properties (Kabat et al., 1944 Shapiro et al., I960). Their synthesis starts from phthalic acid dimethylester (29). In the presence of metallic sodium this compound reacts with methyl-/-butyl ketone (pinacolon, 30) to produce 2-pivaloylindane-l,3-dione (pindone, 31). 

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