Vinyl propionate, reaction

Table 10. Arylated and vinylated propionates by palladium-catalyzed reaction of zinc homoenolate (Ref. [29,40])...

Initially, kinetic resolutions of 2-(trimethylsilyl)-5-[l -(2, 2, 2 -trifluoro-l -hydroxy-ethyl)]furan with a wide variety of lipases and vinyl alkanoates were examined in 1,2-dichloroethane. On the basis of these results, the system consisting of an enzyme (Novozym 435, Candida antarctica, Novo Nordisk Co. Ltd.) and vinyl propionate was sufficient to obtain optical pure alcohol and ester with a high -value. Moderate effect on the optical purity was observed on changing the organic solvents. Obviously, Novozym 435-CH2ClCH2Cl system is the most convenient practical system for obtaining the optically pure alcohol and the ester on the basis of comparison of the reaction time and the -value. 

Racemic l-dimethylamino-2-propanol (100.0 g, 0.97 mol) was stirred with vinyl propionate (63.6 ml, 0.58 mol) at 40°C and Novozym 435 (5.0 g) was added. The reaction was stirred slowly for 75 h and after this time TLC (10% methanol/dichloromethane-visualize KMn04 solution) indicated that the reaction had gone to at least 50% conversion. The enzyme was removed by filtration and the filtrate was distilled at reduced pressure. S-(+)-l-Dimethylamino-2-propanol was obtained as a colourless oil (31.6 g, 64%), boil point 35°C. 

It has been shown that it is the vinyl group that is transferred in this reaction, not an alcoholic one as in acid- or alkali-catalyzed transesterification of esters with saturated alcoholic components. With 0-labeled acetic acid in the transvinylation of vinyl-propionate, the labeled oxygen remained completely in the acetate group [68]. 

In order to optimize and/or improve the behaviour of bioprocesses in ionic liquids/supercritical carbon dioxide biphasic systems, a better understanding of the chemical reaction and mass-transfer phenomena in these biphasic systans is required. In this context, de los Rfos et al. [38] analysed the chemical reaction and the mass-transfer phenomena in the synthesis of bntyl propionate from vinyl propionate and 1-butanol catalysed by CaLB immobilized on dynamic monbranes at... 

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]...

One of the most common substrates is vinyl acetate, leading to 2-acetoxypropanal with up to 98% ee125 if the reaction is carried out in the presence of orthoformate. Vinyl propionate and vinyl benzoate can also be used (see Table 7)75,167. All these substrates are prostereogenic building blocks, e.g, as precursors for the asymmetric preparation of a-amino acids, such as threonine. 

The first example in the Hterature of continuous-flow biocatalysis using SILP catalyst with a SCCO2 stream was published by Lozano et al. [60]. They grafted the ILs over a polymeric monolithic material and then immobiUzed the enzyme Candida antarctica lipase B (CALB) by simple adsorption of an aqueous solution of the enzyme. With this system, they performed the transesterification reaction of vinyl propionate and citroneUol (Figure 18.13). 

Figure 18.13 Vinyl propionate and citroneUol transesterification reaction.

R and R can be acyl, aryl, or alkyl. The formation of acetate or diester is suppressed by low temperatures and optimal reaction times. In the vinylization of different types of reagent, the equilibrium is strongly directed toward one side of the reaction. The vinylization can only occur in the direction of vinyl ester vinyl aryl ether -> vinyl alkyl ether. Poly(vinyl propionate) is also used as an adhesive. 

There are now hundreds of examples, both in the academic and also patent literature, of the use of lipases and esterases for the KR of racemic alcohols. A typical example (Scheme 4.6) is the lipase from Candida antarcHca lipase B (CALB - also known as Novozyme 435), used to resolve an intermediate in the synthesis of (R)-methadone [10]. Thus, the racemic substrate l-dimethylamino-propan-2-ol was treated with CALB in the presence of vinyl propionate that served not only as the acyl donor but also as the solvent. Both CALB and vinyl propionate were selected from an initial screen of different lipase/acyl donor combinations, and this pairing was found to be optimal in terms of reaction rate and enantioselectivity. The preparative scale reaction was ultimately run at 50% w/w concentration on a 1 kg scale to provide the (R)-ester in 45% yield and with an enantiomeric excess of 95%. 

Fig. 4. Trans-vlnylation on carbon-emchoj ed palladlijm chlorides (on the ordinate axis conversion ol vinyl acetate Into vinyl propionate Initial propionic acld/vlnyl acetate ratio 10 v/v static reactor, 50 °C, 34.50 as support, content of supported palladium 1 vt.% (a,b,c1) and 0.5 wt.% (c2), formal concentration of palladium in the reaction mlxtiore ca. 6 (a,b,c1 ) and 2 mg-atom/1). Catalysts ...

In order for the prcx ess to be more practical at large scale a number of improvements were made. As described previously, vinyl butyrate was found to be the most selective acyl donor. However, in consideration of scale-up costs, vinyl butyrate was much more expensive than vinyl propionate. Furthermore, the smell associated with butyrates was an added process consideration. Since vinyl propionate was only slightly less selective than vinyl butyrate (around 5% d.e.), on balance it was decided to scale up the biotransformation with vinyl propionate. In addition, MTBE was replaced with heptane as the reaction solvent. This prevented the solvent swap required for the diol/ester partition. The change in solvent gave no loss in selectivity. This was thus a very volume-efficient resolution that could be performed in standard chemical vessels without the need for any specialized equipment. After flie reaction was complete the workup was performed as outlined previously. This process was scaled up to 40-kg input batches of racemic/meso diol without complication. 

The combination of a resin and covalently supported IL with SCCO2 was also used in the KR and dynamic kinetic resolution (DKR) of 1-phenylethanol with vinyl propionate catalyzed by Candida antarctica lipase B (CALB) [125]. The IL molecule covalently supported on Merrifield resin was realized through the reaction of 1-butyl imidazole with chloromethylated resin. Subsequently, NTf2 was introduced via ion exchange. Under improved conditions, the conversion of 1-phenylethanol was 50% with 99.9% ee to the product. In order to develop a more efficient process, the KR of 1-phenylethanol was tested on a flow system, and it remained stable for 6 days with 99% ee Moreover, by combing two fixed-bed reactors loaded with the supported enzyme (biocatalytic reactor, CALB-SILLP (SILLP, supported ionic liquid-like phase) 11, 150 mg) and an additional one with an acid zeolite (chemical racemization catalyst, 100 mg). Figure 2.40, the DKR of 1-phenylethanol... 

Water also causes a change in the reaction medium, which may be advantageous. A drawback of the reducing medium in the Eastman process is that in addition to acetic anhydride, the by-product ethylidene diacetate is formed, CH3CH(AcO)2. This can be thermally decomposed to vinyl acetate and acetic acid, or it can be reduced to ethyl acetate, which in the recycle would lead eventually to propionic acid. 

Uses Solvent for nitrocellulose cellulose acetate cellulose acetobutyrate cellulose aceto-propionate, waxes, fats, dyestuffs, vinyl, and alkyd resins experimental propellant fuel additive organic synthesis (FriedeLCrafts reactions) manufacture of pharmaceuticals and pesticides. 

The dimerization of functional alkenes such as acrylates and acrylonitrile represents an attractive route to obtain bifunctional compounds such as dicarboxylates and diamine, respectively. The head-to-tail dimerizahon of acrylates and vinyl ketones was catalyzed by an iridium hydride complex generated in situ from [IrCl(cod)]2 and alcohols in the presence of P(OMe)3 and Na2C03 [26]. The reaction of butyl acrylate 51 in the presence of [IrCl(cod)]2 in 1-butanol led to a head-to-tail dimer, 2-methyl-2-pentenedioic acid dibutyl ester (53%), along with butyl propionate (35%) which is formed by hydrogen transfer from 1-butanol. In order to avoid... 

Among the characterized metal homoenolates, only zinc homoenolate of alkyl propionate undergoes substitution reactions with electrophiles under suitable conditions. Two types of metal catalysts, copper(I) and metals of the nickel triad (e.g. Pd), have successfully been used to effect allylation, arylation, and vinylation reactions. 

Reduction of add chlorides (8, 461).2 Acid chlorides can be selectively reduced to aldehydes by slightly less than 1 molar equivalent of NaBH4 in a mixture of DMF THF at - 70°. It is essential to minimize further reduction by quenching the reaction with a mixture of propionic acid-dilute HC1 and ethyl vinyl ether (caution H2 is evolved). Both aliphatic and aromatic aldehydes can be obtained in 80-95% yield. 

In almost all of the transformations described above it has been assumed that both vinyl groups of protoporphyrin-IX (19) have been affected. Obviously, by judicious control of stoichiometry it is possible in many cases to effect only partial transformations of protoporphyrin-IX in which only one vinyl group has been modified. Under these circumstances a mixture of the 3-vinyl and 8-vinyl derivatives results, and in a number of situations these isomers can be isolated, separated and characterized. In order to purify almost all of the compounds shown in Scheme 8, it is usually necessary to esterify the propionic acid groups on the 13- and 17-positions so that the products can be effectively chromatographed, usually on alumina or silica. Indeed, in many instances the reactions are carried out on the dimethyl ester derivatives, and this enables normal organic solvents to be employed. 

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