R-Butyl acetate

Alkali metal alkoxides, r-butyl acetate neat, 45°, 30 min, 98% yield of r-butyl ester from methyl benzoate. The rate constant for the reaction increases with increasing ionic radius of the metal and with decreasing polarity of the solvent. Equilibrium for the reaction is achieved in <10 sec. Other examples eire presented. " ... 

Fig. 10 Excess acidity plots against X for the hydrolyses of some esters in aqueous H2SO4 at 25°C for methyl benzoate (open circles) and methyl 2,6-dimethylbenzoate (closed circles), data from ref. 41, and for r-butyl acetate (open triangles), data from ref. 29. PCT, protonation correction term.

An alternate, shorter route was also developed which involved reaction of the alcohol derived from 27 with 3-4 equivalents of hthium r-butyl acetate to afford an excellent 75-80% yield of hydroxyketone 31 without the need for pnor protection of the alcohol and with no detectable reaction with the nitrile (Scheme 7). Although these routes still involved a low-temperature reduction, both could be scaled to kilogram... 

Addition of r-butyl acetate to lithium diisopropylamide (LDA) in hexane at - 78°C gives the lithium salt of r-butyl acetate456 (2-22) as a stable solid. The nmr and ir spectra of this... 

Preparation.l Dialkyl acetals of DMF are generally prepared by transacetal-ization of the dimethyl or diethyl acetal, but this reaction is not useful in the case of the di-r-butyl acetal. Replacement of one methoxy group of DMF dimethyl acetal occurs on refluxing in f-butyl alcohol conversion to the dw-butyl acetal is effected in the presence of 2,4,6-tri-f-butylphenol (equation I). 

As indicated by the position of lsO in the product, the acid-catalyzed hydrolysis of r-butyl acetate in water enriched in lsO does not follow the mechanism for the reverse of Fischer esterification, shown in Figure 19.3. Suggest a mechanism that explains the position of the lxO in the product and explain why this mechanism is favored in this case. 

Preparative Methods conveniently prepared - by reaction of the magnesium enolate of r-butyl acetate (readily made with Bromomagnesium Diisopropylamide) with (-)-(lR,2S,5R)-Menthyl (S)-p-Toluenesulfinate (eq 1). It was also made in 91% yield by reacting a solution of Lithium Diisopropylamide with (R)-(+)-methyl p-tolyl sulfoxide and 7-butyl carbonate (eq 2). It should be noted that asymmetric oxidation of 7-butyl 2- p-tolylsulfinyl)acetate with a modified Sharpless reagent gave a... 

The effectiveness of lead tetra-alkyls can be degraded by the presence of sulphur compounds and enhanced by certain organic co-anti-knocks. Graiff [44] has shown that the latter effect is due to the formation of different forms of lead monoxide (red and yellow), with different catalytic activities [39]. The co-anti-knocks may be carboxylic acids or esters like r-butyl acetate [45] but, surprisingly, r-butyl and cumene hydroperoxides also work as co-anti-knocks with lead [44]. That is, when added to leaded... 

Diethylaluminum enolates can be produced regiospecifically through reaction of diethylaluminum chloride and zinc dust with a-bromo ketones and esters (Scheme 32).122 Obviously zinc is involved in this reaction, but the mild conditions are in sharp contrast to the Reformatsky reaction and support the existence of an aluminum enolate in this process. The same type of enolate can be obtained from r-butyl acetates and diethylaluminum 2,2,6,6-tetramethylpiperidide (DATMP), which is generated in situ from diethylaluminum chloride and LITMP (Scheme 33).123... 

Note that the anion of diethyl malonate requires a more polar solvent than THF. 7r-(Fluorobenzene)chromium tricarbonyl is more reactive than (1) the corresponding iodo complex is less reactive than (1). The reaction appears to be fairly limited. Thus the anions of 1,3-dithiane, r-butyl acetate, acetonitrile, and acetophenone fail to react with (1),... 

None of the products formed in the reactions described above is considered to significantly change the reaction rates and product distributions by acting as a catalyst. However, Siskin et al. [106] reported that in the hydrolysis of methyl 1-naphthoate at 343 °C naphthalene was predominantly formed because the potential for autocatalysis arises. They concluded that decarboxylation of naphthoic acid, the main product at a lower temperature of 250 °C, led to the formation of naphthalene at 343 °C the reaction is catalyzed by the generated carbonic acid. In the hydrolysis of typical p-keto esters, ethylacetoacetate was completely converted to acetone, eAanol, and CO2 within 30 min at 250 °C. Under the same conditions, r-butyl acetate degraded into a bright red, insoluble mixture of unidentifled products resulting from polymerization of isobutylene [107]. 

Esters Me acetate Et acetate /-Propyl acetate r)-Butyl acetate Cellosolve acetate... 

A valuable method for converting one alkoxide to another is an ester exchange reaction [20], This method is particularly suited for the preparation of the tertiary butoxide from the isopropoxide and r-butyl acetate. The reaction is as follows ... 

More modem variations include the use of p-methylthiovinylketones, as 1,3-dicarbonyl synthons, in combination with the enolate anion of r-butyl acetate. ... 

Transacetalization, usually starting from the dimethyl acetal, is an important method for the preparation of amide acetals (465 Scheme 86) with long chain or secondary alkyl groups7 4 83t3235 Recently a method was described which allows the preparation of even the di-r-butyl acetal of DMF by transace-talization. To achieve good yields it is necessary to drive the equilibrium reaction to completion by distilling off the alcohol formed. Cyclic acetals (467) or dithioacetals (466) can be more easily synthesized by transacetalization. 24 28-3i-32,35... 

A variety of bases have been used in the palladium-catalyzed a-arylation of carbonyl derivatives. The pKa of the carbonyl moiety determines the choice of the base. The preferred bases for the a-arylation with ester derivatives are either NaHMDS (f-butyl propionate) or LiHMDS (r-butyl acetate) as KHMDS was reported to lead to lower yield because of competing hydrodehalo-genation. More sensitive substrates such as a-imino esters, malonates, or cyanoesters required the use of a milder base, as decomposition was observed with HMDS bases. 

Less hindered bases can be used to form the enolate, provided tertiary butyl. esters are employed to retard reactions at the carbonyl group. For example, lithium amide in liquid ammonia has been successfully used for the alkylation of r-butyl acetate. 

In this reserpine synthetic route (Scheme 3.21), Diels-Alder reaction of dihydropyridine 133 (100) and methyl a-acetoxyacrylate 134 afforded iso-quinuclidenes 135 and 136 (36). Addition of lithium r-butyl acetate to 135 afforded the )8-ketoester 137 which was converted to the corresponding enol ester 138. When 138 was refluxed in xylenes, the cis-fused hexahydroiso-quinoline 139, in which the reserpine C(15), C(16), and C(20) stereocenters are in place, formed in good yield. Hydrogenation of the enamine function in 139 followed by reduction of the enol ester afforded 140 which has the C(17)-methoxy group with the required relative stereochemistry. Acylation of ketone 140 yielded the C(18), C(19) enol ester which was hydrogenated stereoselectively to produce 141 in which the C(18) stereochemistry is set. Deprotection of the nitrogen function followed by tryptophylation afforded 142 which was then cyclized to provide the anticipated isoreserpine diol 143... 

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