2- butanone, reaction with lead

In contrast, highly stereoselective aldol reactions are feasible when the boron etiolates of the mandelic acid derived ketones (/ )- and (5,)-l- t,r -butyldimethylsiloxy-l-cyclohexyl-2-butanone react with aldehydes33. When these ketones are treated with dialkylboryl triflate, there is exclusive formation of the (Z)-enolates. Subsequent addition to aldehydes leads to the formation of the iyn-adducts whose ratio is 100 1 in optimized cases. 

What does all of this mean The reaction of 2-pentanone with LDA in THF at -78°C constitutes typical kinetic control conditions. Therefore, formation of the kinetic enolate and subsequent reaction with benzaldehyde to give 34 is predictable based on the kinetic versus thermodynamic control arguments. In various experiments, the reaction with an unsymmetrical ketone under what are termed thermodynamic conditions leads to products derived from the more substituted (thermodynamic) enolate anion. Thermodynamic control conditions typically use a base such as sodium methoxide or sodium amide in an alcohol solvent at reflux. The yields of this reaction are not always good, as when 2-butanone (37) reacts with NaOEt in ethanol for 1 day. Self-condensation at the more substituted carbon occurs to give the dehydrated aldol product 38 in 14% yield. Note that the second step uses aqueous acid and, under these conditions, elimination of water occurs. 

Write out the reaction of 2-methylcyclohexanone under kinetic conditions (choose the base) that will lead to the kinetic aldol product in a subsequent reaction with 2-butanone. 

A variation of the malonic ester synthetic uses a P-keto ester such as 116. In Section 22.7.1, the Claisen condensation generated P-keto esters via acyl substitution that employed ester enolate anions. When 116 is converted to the enolate anion with NaOEt in ethanol, reaction with benzyl bromide gives the alkylation product 117. When 117 is saponified, the product is P-keto acid 118, and decarboxylation via heating leads to 4-phenyl-2-butanone, 119. This reaction sequence converts a P-keto ester, available from the ester precursors, to a substituted ketone in what is known as the acetoacetic acid synthesis. Both the malonic ester synthesis and the acetoacetic acid synthesis employ enolate alkylation reactions to build larger molecules from smaller ones, and they are quite useful in synthesis. 

Using the relative rate method. Chew et al. (1998) have determined an upper limit of the rate coefficient for the NO3 reaction with 2-butanol, k < (2.6 0.8) x 10 cm molecule" s at 298 K (table II-B-17). The measurement was possibly affected by reaction of 2-butanol with N2O5 (gas-phase or heterogeneous) to form nitrates as observed by Langer and Ljungstrom (1995). The preferred value recommended by lUPAC (2008) is determined from a combination of the rate coefficient and product yield of 2-butanone measured by Chew et al. (1998), assuming that the reaction occurs almost exclusively by H-atom abstraction from the tertiary C—H bond. This procedure leads to k = 2.0 x 10 cm molecule" s at 298 K. 

Acetaldehyde can be used as an oxidation-promoter in place of bromine. The absence of bromine means that titanium metallurgy is not required. Eastman Chemical Co. has used such a process, with cobalt as the only catalyst metal. In that process, acetaldehyde is converted to acetic acid at the rate of 0.55—1.1 kg/kg of terephthahc acid produced. The acetic acid is recycled as the solvent and can be isolated as a by-product. Reaction temperatures can be low, 120—140°C, and residence times tend to be high, with values of two hours or more (55). Recovery of dry terephthahc acid follows steps similar to those in the Amoco process. Eastman has abandoned this process in favor of a bromine promoter (56). Another oxidation promoter which has been used is paraldehyde (57), employed by Toray Industries. This leads to the coproduction of acetic acid. 2-Butanone has been used by Mobil Chemical Co. (58). 

The thin-layer chromotography (TLC) monitoring of the reaction (Scheme 28) leads to a conclusion that the anomalous l-vinyl-2-methylpyrrole (53) is a secondary product from the pyrrole (54). When reacting with excess acetylene in an autoclave at 100°C, l-hydroxy-2-methyl-3-butanone oxime (55) gives two anomalous products, 2,3-dimethyl-1-vinylpyrrole (56), which was also reported (78IZV2426), and 2-(l-propeny 1-2)-1-vinylpyrrole (57) in 20 and 8% yields respectively (Scheme 28). 

Reaction of N-substituted bromomethanesulfonamides with 2 equiv of potassium carbonate and an cr-haloketone, ester, or nitrile leads directly to the /3-sultams 187 substituted at the C-3 position by an EWG. This base-promoted condensation can be used with a-halo ketones, esters, and nitriles where a second Sn2 intramolecular displacement can operate in tandem fashion (Scheme 60). This domino alkylation sequence exhibits a reactivity order where ketone > nitrile > ester (Table 14). The process is particularly efficient when diethyl bromomalonate or 3-chloro-2-butanone are involved <2004CJC113>. 

Another side reaction, caused by changes in the solvent composition, was studied in 1980 (in the former USSR) and, unfortunately, was also published in rather inaccessible journals [37]. The reactions of phenylmagnesium bromide with the aliphatic ketones, 2-butanone and 3,3-dimethyl-2-butanone (methyl-fcrt-butyl ketone), were studied. Besides the carbonyl addition reaction, leading to a tertiary alcohol, enolization also takes place with this type of ketones. The enolate, on hydrolysis, yields the starting ketone however, before hydrolysis, in the reaction mixture of the Grignard reagent and the ketone, the enolate can react further with the ketone to form a condensation product (Scheme 16). 

Butanone 29 was also investigated as an aldol donor. The reactions of 2-buta-none 29 with nitro-substituted benzaldehydes afforded the aldol product 30 with excellent stereoselectivity (up to 93 7 of dr and 98% ee). However, the reaction also occurred unselectively at the Cl position of the ketone, leading to the concomitant formation of 31 (Scheme 8.10). 

Cyclobutanones. Reaction of methyl methylthiomethyl sulfoxide with 1,3-dibromopropane in the presence of 2 eq. of potassium hydride leads to cyclo-butanone dimethyl dithioacetal S-oxide (2) in high yield. Intermediates (a)... 

Using a condensed reaction form, treatment of 2-butanone with NaBI leads to 2-butanol, and the first step delivers the hydrogen marked in blue in the illustration, whereas aqueous ammonium chloride (a weakly acidic solution) is the second step that delivers the hydrogen marked in red. Sodium borohydride reduces both ketones and aldehydes. Indeed, the reduction of an aldehyde with NaBH4 is somewhat easier than the similar reduction of a ketone. Aldehydes are easier to reduce than ketones because the carbonyl unit is less stericaUy hindered. 

The reaction of 2,2-dimethyl-2-butanone and a peroxyacid leads to ter/-butyl acetate. Draw both reactant and product. With this reaction in mind, surest a reaction sequence that will convert 1-pentene to tert-butyl pentanoate. 

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