2- Butanone, alkylation

Hydroxy-2-butanone (alkyl ketone) 3-Hydroxy-4,5-dimethyl-2(5H)-furanone (= Sotolon) (furanone)... 

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). 

Alkyl substituents stabilize a carbonyl group m much the same way that they sta bilize carbon-carbon double bonds and carbocations—by releasing electrons to sp hybridized carbon Thus as then heats of combustion reveal the ketone 2 butanone is more stable than its aldehyde isomer butanal... 

Ethyl acetoacetate may also be subjected to double alkylation Show how you could prepare 3 methyl 2 butanone by double alkylation of ethyl acetoacetate ... 

Derivatives. Small amounts of alkyl quiaolines are present ia the tars resulting from the carbonization and Hquefaction of coal (111). Good yields of 4-methyl quinoline, 4,6-dimethyl quinoline [826-77-7], and 4,8-dimethyl quinoline [13362-80-6] are obtained from 4-(diethylamino)-2-butanone and the appropriate aniline. This approach is a promising addition to the traditional syntheses discussed eadier (112). Vlaylacetylene reacts with mercuric chloride and either aniline or -toluidine to yield 4-methyl- and 4,6-dimethyl quinoline, respectively (113). 

Many 3-substituted indoles have also been prepared with the use of a-alkyl or a-aryl-p-keto sulfides. Thus indolization of aniline 5 with 3-methylthio-2-butanone 27 furnished indolenine 28, presumably via the same mechanism discussed earlier. The indolenine 28 was relatively unstable and reduced to the indole 29 without purification. Tetrahydrocarbazole 32 was prepared in 58% overall yield. Smith et al. made excellent use of the Gassman process in the total synthesis of (-i-)-paspalicine and (+)-paspalinine. ... 

Dimethoxy-2-(arylimino)-2,3,6,7-tetrahydro-4//-pyrimido[6,1 -n]iso-quinolin-4-ones were N-alkylated with A-(catalytic amount of I2 in boiling 2-butanone in 13-67% yields (00MIP19). 

Starting from n-butane, 2-butoxides that rapidly convert to 2-butanone are found over MgCr204 [24]. However, the further oxidation of adsorbed 2-butanone only gives rise to the acetate species, while starting from n-butane, formate species are also observed. This can be explained assuming that sec-butoxides can partly isomerize to rert-butoxides before further oxidation. This implies that the C-O bond formed is partly ionic and the alkyl moiety has the... 

The equilibrium ratios of enolates for several ketone-enolate systems are also shown in Scheme 1.1. Equilibrium among the various enolates of a ketone can be established by the presence of an excess of ketone, which permits reversible proton transfer. Equilibration is also favored by the presence of dissociating additives such as HMPA. The composition of the equilibrium enolate mixture is usually more closely balanced than for kinetically controlled conditions. In general, the more highly substituted enolate is the preferred isomer, but if the alkyl groups are sufficiently branched as to interfere with solvation, there can be exceptions. This factor, along with CH3/CH3 steric repulsion, presumably accounts for the stability of the less-substituted enolate from 3-methyl-2-butanone (Entry 3). 

The acetone-sensitized photodehydrochlorination of 1,4-dichlorobutane is not suppressed by triplet quenchers (20), but the fluorescence of the sensitizer is quenched by the alkyl chloride (13). These observations imply the operation of a mechanism involving collisional deactivation, by the substrate, of the acetone excited singlet state (13,21). This type of mechanism has received strong support from another study in which the fluorescence of acetone and 2-butanone was found to be quenched by several alkyl and benzyl chlorides (24). The detailed mechanism for alkanone sensitization proposed on the basis of the latter work invokes a charge-transfer (singlet ketone)-substrate exciplex (24) and is similar to one of the mechanisms that has been suggested (15) for sensitization by ketone triplets (cf. Equations 4 and 5). 

Cyclization occurred at the N-3 atom when 4-(3-bromopropylaruino)-l, 6,7,1 1 b-tctrahydro-2//-pyrimido[6,l -zz -isoquinoline was treated with NaH to give a tetracyclic derivative <2003M1271>. 9,10-Dimethoxy-2-(arylimino)-2,3,6,7-tetrahydro-4//-pyrimido[6,l- ]isoquinolin-4-ones were N-3-alkylated with iV-(ra-bromoalkyl)phthalimides in the presence of K2C03 and a catalytic amount of I2 in boiling 2-butanone in 13-67% yields <2000W020/058308>. Treatment of the 2-[(4-methoxyphenyl)methyl] derivative of 2,3,6,7-tctrahydro-l //,5//-pyrido[3,2,l-/ylqninazolinc-... 

The use of the trisylhydrazone 124 of 2-butanone 123 in the coupling process provides access to products containing an ethyl-substimted olefin 126. The starting unsymmetrical hydrazone 124 undergoes deprotonation and alkylation at the terminal a-carbon leading to a single metallated olefinic product 125Li (equation 44). The electrophilic component 2,3-dibromopropene leads to 126, which can be further elaborated via subsequent reactions. 

The kinetics of the base-catalysed alkylation of 5-substituted 3-nitrotriazoles with methyl vinyl ketone to give the N(l)-3-butanone derivative has been studied and the reaction was shown to be first order in both mvk and the 3-nitrotriazolium anion <90JOU1170>. 

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. 

An extension of the above preparative method of chirality transfer is the preparation of dioxolanes 16 from lactic acid and 3,3-dimelhyl-2-butanone (pinacolone)80. In this case the crude cis/trans ratio is already 95 5, thus, it is much better than the observed 80 20 ratio observed with trimethylacetaldehyde. Alkylation of 16 with benzyl bromide seems to proceed with a satisfactory 95 5 selectivity. 

Die Umalkylierung von cyclischen N-Methyl-aminen (z. B. 1-Methyl-piperidin, Morphin-Alkaloide) laBt sich in zwei Stufen durch Quaternisierung mit einem Alkyl-halogenid und Demethylierung des isolierten Quatemisierungsproduktes mit Natrium-benzolthiolat in siedendem Butanon/Acetonitril erreichen5 (vgl. S. 1221) ... 

Problem 17.43 Show how acetone can be converted into 4-phenyl-2-butanone using enamine alkylation. M... 

Direct alkylation of indoles under neutral conditions has been observed for especially reactive alkyl halides. 3-Methylbutenyl bromide gives the 3-substituted indole in acetic acid-sodium acetate at room temperature (equation 170) (69TL2485). At higher temperature in acidic solution, 1,2-dimethylindole undergoes bisallylation (equation 171) (67CJC2628). a-Halo ketones including bromoacetone, 3-bromo-2-butanone and 2-chlorocyclohexanone can alkylate 2-substituted indoles in aqueous acetic acid, but the acidic conditions used in these reactions would probably be destructive of indole itself (72JOC2010). 

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