Pinacolone oxidant

To meet the needs of the advanced students, preparations have now been included to illustrate, for example, reduction by lithium aluminium hydride and by the Meerwein-Ponndorf-Verley method, oxidation by selenium dioxide and by periodate, the Michael, Hoesch, Leuckart and Doebner-Miller Reactions, the Knorr pyrrole and the Hantzsch collidine syntheses, various Free Radical reactions, the Pinacol-Pinacolone, Beckmann and Arbusov Rearrangements, and the Bart and the Meyer Reactions, together with many others. 

The pinacolone may be employed for the preparation of trimethylacetlc acid (plvallc acid) by oxidation with sodium hypobromite solution ... 

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. 

Dienones of this class are useful starting materials for the preparation of bicyclic compounds via Diels-Alder reactions1 4 and for the synthesis of small ring compounds.6 The 2,4-dienone can be converted quantitatively to the 2,5-isomer by treatment with fuming sulfuric acid and subsequent hydrolysis.6 The oxidation procedure is also applicable to the conversion of mesity-lene to mesitol or of isodurene to isodurenol,7 and can be used to convert tetramethyl ethylene quantitatively and directly to pinacolone.8... 

A thermal oxidation of 2,3-dimethyl-2-butene, 16, occurs in NaY when the temperature of the oxygen-loaded zeolite in raised above — 20°C [35], Similar thermally initiated oxidations were not observed for the less electron rich tram-or cix-2-butene. Remarkably, pinacolone was conclusively identified as one of the products of the reaction of 16, This ketone is not a product of the photochemical Frei oxidation (vide supra) and underscores the very different character of these two reactions and the complexity of the oxygen/16 potential energy surface, A rationale for the different behavior could lie in the different electronic states of the reactive oxygen-CT complex in the thermal and photochemical reactions. Irradiation could produce an excited triplet-state CT complex ( [16 O2] ) and/ or ion pair ( [16 02 ] ) with different accessible reaction channels than those available to a vibrationally excited ground-state triplet complex ( [16 "02]) and/... 

It has been found that 3-azapyrylium salts 57 and 58 are obtained in reactions of pinacolone as well as vinyl chlorides 59 with N-acylnitrilium salt 56 (91ZOR2479 92ZOR2577). The acylation of vinyl chlorides 59 in benzonitrile also leads to salts 60 (91ZOR1986). The same salts 55 are formed as intermediates by acylation of acetylenes in the presence of nitriles (88ZOR1605). Vinyl chlorides and acetylenes are both direct derivatives of carbonyl compounds with the same oxidation level (72MI2 85KGS1443). 

In the examples given the preparative value depends upon the ready availability of the required methyl ketone thus pinacolone (Expt 5.98), cyclopropyl methyl ketone (Expt 7.1) and mesityl oxide (Expt 5.213) are converted into 2,2-dimeth-ylpropanoic acid, cyclopropanecarboxylic acid and 3,3-dimethylacrylic acid respectively (Expts 5.124 and 5.125). 

The syntheses of benzo[e] and benzo[g]indoles have been performed by reaction of 2-amino-1-bromo or l-amino-2-bromonaphthalene with the anion of pinacolone (67% and 82% yields, respectively). The reaction with the anion CH2COCH(OMe)2, affords the 2-formyl indoles (52% and 65% yields, respectively), which can be oxidized to the corresponding acids [90]. 

Cleavage of ketones by oxidation is infrequently used for preparation of monocarboxylic acids. Trimethylacetic acid is made in 75% yield from pinacolone, (CHj)jCCOCHj, by oxidation with chromic anhydride in aqueous acetic acid. Cleavage on only one side of the carbonyl group is possible in this case. 

An oxidizable alkyl group is not necessarily attached to an aromatic nucleus. Oxidation of a methyl group of trimethylacetic acid by heating for 7 hours with alkaline permanganate gives dimethylmaIonic acid (35%). Other examples include the a-keto acids, trimethylpyruvic acid (40%) ° from pinacolone and /3-naphthylglyoxylic acid (40%) from -acetyl-naphthalene. 

The reaction of the lithio derivative of the diethyl acetal of the polyenynal 304 with the polyenyne ketone 305 followed by acid hydrolysis gave the hydroxyaldehyde 306. The ethynyl ketone 307 obtained by the aldol condensation of 306 with pinacolone was ethynylated" to give 308. Oxidative coupling of 308 yielded the... 

Pinacolone (rert-butyl methyl ketone) is transformed into pivalic acid (trimethylacetic acid) in 71-74% yield [737], Mesityl oxide is converted into 3,3-dimethylacrylic acid in 49-53% yield [703], Isopropenyl methyl ketone gives methacrylic acid in 41% yield [697], and pregnenolone acetate furnishes 3-acetoxyetienic acid in 91-95% yield [117J] (equations 421-424). 

Preparation of Monomers. Methyl vinyl ketone (MVK) was obtained from Pfizer Chemical Division, New York, and distilled to remove the inhibitor. Methyl isopropenyl ketone (MIPK) was prepared by the aldol condensation of methyl ethyl ketone and formaldehyde, according to the method of Landau and Irany 0. The major impurity in this monomer is ethyl vinyl ketone (5. The monomer was redistilled before use. 3 Ethyl 3 buten 2 one (EB) was prepared by the aldol condensation of methyl propyl ketone and formaldehyde. Ethyl vinyl ketone (EVK) was prepared by a Grignard synthesis of the alcohol, followed by oxidation to the ketone. t-Butyl vinyl ketone (tBVK) was prepared from pinacolone and formaldehyde by the method of Cologne (9). Phenyl vinyl ketone (PVK) was prepared fay the dehydrochlorlnatlon of 0 cbloro propiophenone (Eastman Kodak). Phenyl isopropenyl ketone (PPK) was prepared by the Mannich reaction using propiophenone, formaldehyde and dimethylamine HCl. 

It is evident that the crucial step for the reaction is the generation of the transitory carbonium ion (XIII). Further support of this general scheme for the reaction is that other processes which would be expected to produce the same carbonium ion give exactly the same reaction. Thus pinacol bromohydrin (XIY) leads to pinacolone when it is treated with silver nitrate or silver oxide,13 and the same product is obtained by the action of nitrous acid on 2,3-dimethyl-3-amino-2-butanol (XV).14... 

Preparation carbonation of 1-butylmagnesium chloride (61-70%) hypobroraite oxidation of pinacolone (71 -74%). ... 

A 1,2-hydride shift As formulated (Scheme 12.2), the reaction could be considered an aza-analogous pinacol-pinacolone rearrangement. However, it seems doubtful that the C=N + < heterolysis on its own is efficient enough to pull off this self-oxidation/reduction. 

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