3- Hydroxy-2-butanone, addition

Out first example is 2-hydroxy-2-methyl-3-octanone. 3-Octanone can be purchased, but it would be difficult to differentiate the two activated methylene groups in alkylation and oxidation reactions. Usual syntheses of acyloins are based upon addition of terminal alkynes to ketones (disconnection 1 see p. 52). For syntheses of unsymmetrical 1,2-difunctional compounds it is often advisable to look also for reactive starting materials, which do already contain the right substitution pattern. In the present case it turns out that 3-hydroxy-3-methyl-2-butanone is an inexpensive commercial product. This molecule dictates disconnection 3. Another practical synthesis starts with acetone cyanohydrin and pentylmagnesium bromide (disconnection 2). Many 1,2-difunctional compounds are accessible via oxidation of C—C multiple bonds. In this case the target molecule may be obtained by simple permanganate oxidation of 2-methyl-2-octene, which may be synthesized by Wittig reaction (disconnection 1). 

The addition of phenyllithium to 3-hydroxy-l,3-diphenyl-1-butanone (4. R1 = R3 = C6HS R2 = H) leads to the predominant formation of either one or the other diastereomer, depending on the reaction temperature146. Thus, for this type of addition reaction there are at least two competing mechanisms which have quite different activation entropies147. 

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. 

Additional aldehydes and ketones were also included in the U.S. Nationwide Occurrence Study dimethylglyoxal (2,3-butanedione), cyanoformaldehyde, 2-butanone (methyl ethyl ketone), trans-2-hexanal, 5-keto-l-hexanal, and 6-hydroxy-2-hexanone [11, 13]. Dimethylglyoxal was the most consistently detected of these carbonyl compounds (up to 3.5 pg/L) and was found at higher levels in plants using ozone. Maximum levels of 0.3, 5.0, and 0.7 pg/L were observed for cyanoformaldehyde, 2-butanone, and trans-2-hexenal, respectively 6-hydroxy-2-hexanone and 5-keto-1 -hexanal were only detected in early stages of treatment, and not in finished waters. 

A wide range of donor ketones, including acetone, butanone, 2-pentanone, cyclopentanone, cyclohexanone, hydroxyacetone, and fluoroacetone with an equally wide range of acceptor aromatic and aliphatic aldehydes were shown to serve as substrates for the antibody-catalyzed aldol addition reactions (Chart 2, Table 8B2.6). It is interesting to note that the aldol addition reactions of functionalized ketones such as hydroxyacetone occurs regioselectively at the site of functionaliztion to give a-substitutcd-fi-hydroxy ketones. The nature of the electrophilic and nucleophilic substrates utilized in this process as well as the reaction conditions complement those that are used in transition-metal and enzymatic catalysis. 

Methyl ketones from esters (12, 126).1 The reaction of a carboxylic acid or ester with CH3Li and ClSi(CH3)3 to provide a methyl ketone has been used to obtain a silyl protected (S)-3-hydroxy-2-butanone (2) from ethyl lactate (1). The addition of... 

HOMOCONJUGATE ADDITION, 66 Homo-Michael acceptor, 69 Hydrogen peroxide-acetonitrile, 63 4-Hydroxy-2-butanone, 93... 

To a cold (0 °C) solution of 0.2 g (1.1 mmol) of 4-cyclohexyl-4-hydroxy-3-methylene-2-butanone dissolved in 8 mL of dry benzene is added 0.06 g (0.22 mmol) of vanadyl acetylacetonate, producing a green solution which is stirred for 20 min before dropwise addition of 0.73 mL (2.2 mmol) of 3 M r-BuOOH in 2,2,4-trimethylpentane over 10 min. The resultant red solution is stirred for 10 h at r.t. and the color changes to yellow-brown. The reaction mixture is washed with 4 mL of H20, 4 mL of brine and dried over MgS04. Evaporation of the solvent in vacuo followed by column chromatography (silica gel, petroleum ether/EtOAc 3 1) gives 0.16 g (76%) of pure yyrc-epoxide. 

In addition to the 3-hydroxy-2-butanone and ammonium acetate model reaction as previously studied reaction of 3-hydroxy-2-butanone and... 

At 120°C, both components in this binary indicate positive deviation in one composition range and negative deviation in another (Figure 1.13). The system also indicates a slight maximum pressure azeotrope near a water mole fraction of 0.95 (Figures 1.13 and 1.15). Additionally, a maximum is observed for the activity coefficient of water (Figure 1.14, curve 1) and a minimum for the activity coefficient of 3-hydroxy-2-butanone (curve 2). These phenomena are best represented by the Margules equation. 

Percent product distribution 2-methyl-propanal 48.1 1.1, 2-hydroxy-3-methyl-butanal 6.9 0.34, l-hydroxy-3-methyl-2-butanone 29.5 0.61, 1,2-dihydroxy-3-methy 1-butane 15.5 1.1. Data evaluation in a manner similar to that for 1-butene showed 24 % of OH addition to occur at the inner and 76 % at the outer position of the double bond, = 0.82 0.02, and 38% reaction of... 

Percent product distribution butanone 80.8 1.46, 2-hydroxy-2-methyl-butanal 4.6 0.1, l,2-dihydroxy-2-methyl-butane 14.3 0.3. The addition of OH at the double bond of 2-methyl-1-butene occurs to 10.5 % at the inner and to 89.5 % at the outer position. This results mainly in the formation of a tertiary hydroxyalkyl peroxy radical, which carries no abstractable hydrogen at the... 

If we were prepared to waste one molar equivalent of the Grignard reagent, we can treat 4-hydroxy-2-butanone with two molar equivalents of the Grignard reagent and thereby get addition to the carbonyl group ... 

Scheme 23 also outlines a potential problem with the syjnthesis. The initial attack can occur at either end of the double bond of the 7r-complex, 28, to give the two isomers 29 and 30 in a ratio of 4 1. These two isomers are expected from Wacker chemistry since propene produces both acetone and propanal in about the same ratio from the two modes of addition. However, as shall be discussed below, this is not a serious problem with most a-olefins. The same catalyst oxidizes methyl vinylketone only to 4-chloro-3-hydroxy-2-butanone (29 R = C(=0)CH3). The optical purity was still only about 12%. 

Compound 32 was prepared in four steps from 4-hydroxy-2-butanone (36). Protection of the alcohol ftmction of 36, as a tetrahydropyranyl (THP) ether 37, was acconqjlished with dihydropyran (DHP) and NH4CI catalyst in refluxing THF (24). Wittig reaction of 37 with the ylide from butyl(triphenyl)phosphonium bromide (n-BuLi, THF) resulted in alkylidenation to form 38, but the yield was less than 5%, even with dropwise addition of the ylide to the aldehyde at -78 . Removal of the THP group, followed by oxidation of the alcohol directly to the acid under neutral conditions (PDC in DMF, 33) afforded 32. Mild oxidation conditions are required to prevent migration of the double bond from the 3-position to the 2-position. 

Goodwin and Treble (78a) have reported that the addition of 3-hydroxy-2-butanone-l-C to growing cultures of E. ashbyii led to incorporation of radioactivity into ring A of riboflavin exclusively. One-half of the was in the methyl groups and none in carbons 6 and 7 of the o-xylene moiety. The labeled acetoin was incorporated more effectively than acetate-2-Cn into ring A. 

Secondary Alcohols. In addition to reporting that primary alcohols cause an increased excretion of glucuronic acid, Neubauer (299) claimed a similar effect after administration of isopropyl, sec-butyl and sec-octyl alcohols. In contradiction, Neymark (310) has reported the quantitative transformation of isopropyl alcohol to acetone in the dog. Neuberg and Gott-schalk (303) claimed that in rabbits acetoin (3-hydroxy-2-butanone) forms a glucuronoside, either from acetoin itself or from its metabolite, 2,3-butylene glycol. 

Asymmetric reducing agents based on chiral 9-alkoxy-9-BBN derivatives have been developed and their ability to reduce acetophenone and 3-methyl-2-butanone assessed.Furthermore the new chiral reagent, potassium 9-0-(l,2 5,6-di-O-isopropylidene-a-D--glucofuranosyl)-9-BBNH reduces a-keto esters to the corresponding a-hydroxy esters with optical purities approaching 100% ee. In addition a reagent, based on (R,R) or (S,S)-2,5-dimethylborolane,... 

Signicant new information related to the photodecomposition of some bifiinctional alkyl nitrates has been reported. In addition to absorption spectra of many alkyl nitrates, Roberts and Fajer (1989) also measured the spectra for the bifiinctional 2-nitrooxyethanol. Bames et al. (1993) studied the absorption spectra and photolysis products of several dinitrates 1,2-propandiol dinitrate, 1,2-butandiol dinitrate, 2,3-butandiol dinitrate, l,4-dinitrooxy-2-butene, 3,4-dinitrooxy-l-butene, as well as several bifiinctional nitrates a-nitrooxyacetone, l-nitrooxy-2-butanone, and 3-nitrooxy-2-butanone. Wangberg et al. (1996) reported on the the atmospheric chemistry of the bifiinctional cycloalkyl nitrates 2-hydroxy-cyclopentyl-l-nitrate, 2-oxo-cyclohexyl-1-nitrate, and frans -l-methyl-cycto-l,2-dinitrate. In this section, we will review the findings related to the tropospheric photodecomposition of these multifunctional nitrates. 

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