R-Butyl propionate

Stereoselective Michael additions. In the absence of strong steric effects, the stereochemistry of Michael addition of amide enolates depends on the enolate geometry, with (Z)-enolates giving mainly antf-adducts and (E)-enolates giving mainly syn-adducts.1 Ester enolates show higher stereoselectivity than amide enolates, as shown by the (E)- and (Z)-enolates of r-butyl propionate (1). The (E)-... 

Few ester enolate crystal structures have been described. The lack of structural information is no doubt due to the fact that the ester enolates undergo a-elimination reactions at or below room temperature. A good discussion of the temperatures at which lithium ester enolates undergo this elimination is presented in the same paper with the crystal structures of the lithium enolates derived from r-butyl propionate (163), r-butyl isobutyrate (164) and methyl 3,3-dimethylbutanoate (165). It is significant Aat two of the lithium ester enolates derived from (163) and (165) are both obtained with alkene geometry such that the alkyl group is trans to the enolate oxygen. It is also noteworthy that the two TMEDA-solvated enolates from (163) and (164) are dimeric, while the THF-solvated enolate from (165) exists as a tetramer. 

These tri(alkoxy)titanium enolates, which have low Lewis acidity, are known to react chemoselective-ly with an aldehyde group in the presence of a ketone (equation 4).14 Other uses described by Reetz et al. include the diastereofacially selective additions of ketone and ester enolates to chiral a-alkoxy aldehydes with nonchelation control.15,16 For example, aldol addition of the tri(isopropoxy)titanium enolate of pro-piophenone to the aldehyde (24) leads to only the two syn diastereomers, with the nonchelation adduct (25) favored (equation 5) i.e. Felkin-Anh selectivity is operating. In the case of aldol addition of r-butyl propionate to the same aldehyde (equation 6), highest stereoselectivity for the isomer (26) is obtained using the tri(diethylamino)titanium enolate.17 Very high levels of nonchelation stereoselectivity can also be obtained in the aldol addition to chiral a-siloxy or a-benzyloxy ketones if a titanium enolate of low Lewis acidity is employed, as in equation (7).18... 

Several ester enolates have also been examined by X-ray crystallography. The enolates of r-butyl propionate and f-butyl 3-methylpropionate were obtained as TMEDA solvates of enolate dimers. Methyl 3,3-dimethylbutanoate was obtained as a THF-solvated tetramer. 

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 (r-butyl propionate) or LiHMDS (f-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. 

Although LHMDS was also used with methyl isobutyrate, better yields were obtained for the same reaction with r-butyl propionate and NaHMDS at room temperature. The a-arylation with t-butyl propionate and LHMDS proceeds only at a higher temperature (80 °C). It was shown later that LiNCy2 could also be very effective for this reaction. More sensitive substrates, such as a-imino esters, required the use of milder base as decomposition was observed with LHMDS. Finally, a-arylation of nitrile derivatives was also reported using LHMDS (eq 24). ... 

The Andersen sulphoxide synthesis allows one also to synthesize a variety of a-heteroatom substituted sulphoxides starting from a-heteroatom stabilized carbanions and (—)-(S)-276. The selected examples shown in Scheme 3 are the best illustration of the generality of this approach. The reaction of enolates or enolate like species with (—)-(S)-276 has been used for the synthesis of optically active a-carbalkoxy sulphoxides. For example, treatment of (—)-(S)-276 with the halogenomagnesium enolates of -butyl acetate, t-butyl propionate or t-butyl butyrate resulted in the formation of ( + )-(R)-t-butyl p-toluenesulphinylcarboxylates 298367 (equation 163). 

Papageorgiou and Benezra204 treated chiral r-butyl (-)-(S)- and ( + )-(R)-2-(p-tolylsulfinyl)propionate with an aldehyde, then pyrolyzed the mixture and obtained chiral a-(hydroxyalkyl)acrylate in 75% e.e. Similarly, condensation of the anion of ( + )-(R)-3-(p-tolylsulfinyl)propionic acid 159 with aldehydes was found to give the diastereomeric [i-sulfinyl-y-lactones, (+)-(Sc4,Rc5,Ps)-160a and ( + )-( c4,Sc5,l s)-160b in an approximate ratio of 60 40205. 

Related Reagents. (R)-(+)-r-Butyl 2-(p-Tolylsulfinyl)-propionate (R)-(+)-Methyl p-Tolyl Sulfoxide (R)-(+)-Phenyl (p-Toluenesulfinyl)acetate. 

Preparative Methods the synthesis of this compound was first reported by methylation of (R)-(+)-t-Butyl 2-(p-Tolylsulfinyl)acetate via enolate generation with lithium bases such as n-Butyllithium or t-Butyllithium at 0 °C and with only lodomethane as the alkylating agent (eq 1). The diastereomeric ratio was shown by H NMR to be 50 50 with BuLi and 42 58 with t-BuLi. The title compound was also prepared from (-)-(1R,2S,5R)-Menthyl (S)-p-Toluenesulfinate and the magnesium enolate of t-butyl propionate in 68% yield as a 1 1 ratio of the two possible diastereomers (eq 2). ... 

The condensation of the dilithio derivative of (R)-(+)-3-(p-tolylsulfinyl)propionic acid with protected glycoaldehy-des (O-r-butyl and 0-benzyl) gives 5-alkoxy-4-hydroxy-3-(p-tolylsulfinyl)pentanoic acids, which spontaneously cyclize to the corresponding 3-sulfinyl-4-alkoxymethyl butanolides (eq 4). Pure diastereomers can be separated by flash chromatography and are obtained in comparable amounts. The corresponding optically pure butenolides are obtained by pyrolytic elimination of the sulfoxides and then transformed into natural (-i-)-(/ )-umbelactone (eq5). 

Reaction of the a-carbanion of an alkyl aryl sulfoxide (RCHzSOAr) with aldehydes may give four dia-stereomers. In general, the reaction is highly diastereoselective with respect to the a-sulfmyl carbon, but poorly diastereofacially selective with respect to attack on the carbonyl component. In fact, the a-carb-anion (31) of benzyl r-butyl sulfoxide adds to an aldehyde to produce only two diastereomers (32a) and (32b). As shown in Scheme 10, the selectivity increases when the counterion is Zn . A transition state structure (33) is proposed to account for the anti stereoselection. ° Addition of the dianion of (/ )-3-(p-to-lylsulfinyl)propionic acid (34) to aldehydes affords two main diastereoisomeric P-(p-tolylsulfinyl)-7-lac-tones (35 R = Ph and Bu , ca. 60 40). These isomers (35) were separated by chromatography, and their... 

Fig. 8.4 Initial reaction rate (bars) and selectivity (points) exhibited by free Candida antarctica lipase B for butyl propionate synthesis in supercritical carbon dioxide and in four different ionic liquids/supercritical carbon dioxide systems. The reaction conditions were r=50°C, vinyl propionate 150 mM and 1-butanol 100 Mm [38]...

Figure 1. CL time profiles upon injection ("on") of two forms of the same antioxidant (T.OxlO" M) into the probe solution [50 % cumene in PhCl in the presence of AIBN as an initiator initiation rate was 1.0x10 Ms at 333 K]. Curve 1 displays the response to the injection of Y-(4-hydroxy-3,5-di-r-butyl-phenol) propionic acid taken from its organic-phase (PhCl) stock solution, while curve 2 refers to the effect of the potassium salt of this acid taken from its aqueous solution.

Diastereoselective addition of a propionate unit to an achiral aldehyde is an important process in organic synthesis (see Section 1.7.2.3 for the reaction with chiral aldehydes). This process can be achieved with full control by the judicious choice of a thiol ester and a dialkylboryl triflate. As shown in Scheme 16, the (0)-enolate (19) generated from S-r-butyl propanethioate, dicyclopentylboryl triflate and diisopropylethylamine furnishes, upon reaction with an aldehyde, the anti aldol product (20). The syn product (21) is obtained from the Z(0)-enolate (22) derived from the reaction of 5-phenyl propanethioate with 9-borabicyclo[3.3.1]non-9-yl triflate (9-BBNOTf). 

Munoz, R. Monton, J. B. Burguet, M. C. De la Torre, J. Vapor-liquid equihbria in the ternary system isobutyl alcohol + isobutyl acetate + butyl propionate and the binary systems isobutyl alcohol + butyl propionate, isobutyl acetate + butyl propionate ata 101.3 iiPa. Fluid Phase Equilib. 2005, 238, 65-71... 

Octadccy 1-3 (3,5-dwe r/-butyl -4-hydroxyphenyl) propionate (.Iciadecy 1-3(3,5-di-/er/-buiyl -4-hydroxyphenyl) propionate Octadecy l-3( 3.5 -di-terf- buty 1 4 hydroxy phenyl) propionate Octadecy 1-3(3,5-di-f rf-buty I -4-hydroxyphenyl) propionate Octadecy 1-3(3,5-di-ferf-buty) -4-hydroxyphenyl) propionate 2,2 -Methylen bis 6-(m-butyI-4-niethylphcnol)... 

The methyl ester 3-(3, 5-propionic acid (1) is known as an antioxidant [12] and is characterized by values k = 2.3 X 10 l-mol-l-s f = 2, and this data is confirmed by the present work. However as a result of inhibiting oxidation at presence tert.butyl ester 3-(3, 5 -di-tert.butyl-4 -hydroxyphenyl)-propionic acid (2) reaction proceeds with a specific reaction rate 3.0 x 10 l.mol" s , coefficient of stopping of chain f = 5. 

Lladosa, E. Monton, J. B. Biuguet, M. C. Munoz, R. Isobaric vapor-liquid equiUbria for binary and ternary mixtures of dipropyl ether, 1 -propyl alcohol, and butyl propionate. J. Chem. Eng. Data 2006, 51, 2233-2238. 

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