Applications using unsaturated esters

For internal olefins, the Wacker oxidation is sometimes surprisingly regioselective. By using aqueous dioxane or THF, oxidation of P,y-unsaturated esters can be achieved selectively to generate y-keto-esters (Eq. 3.18).86 Under appropriate conditions, Wacker oxidation can be used very efficiently in transforming an olefin to a carbonyl compound. Thus, olefins become masked ketones. An example is its application in the synthesis of (+)-19-nortestosterone (3.11) carried out by Tsuji (Scheme 3.5).87... 

Simple acyclic a,/ -unsaturated esters are not reactive in the conjugate addition of dialkylzincs. In contrast, nitro-substituted unsaturated esters68 and malonates69 are applicable for this reaction. Using peptide-based chiral phosphine 66, Hird and Hoveyda realized the Cu-catalyzed conjugate addition of Et2Zn to iV-acyloxazolidinones with excellent enantioselectivity (Scheme 21).70... 

Palladium-catalyzed bis-silylation of a,/ -unsaturated ketones using bis(disilanyl)dithiane affords seven-membered ring silyl enol ethers in high yields via 1,4-addition (Equation (48)).8,97 Application of this reaction to a,/ -unsaturated esters and nitriles gives five-membered ring 1,2-addition products in good yields (Equation (49)). 

Applications. Phthalic anhydride is used largely to make plasticizer for polyvinyl chloride. It is also a feed for alkyd resins and. for unsaturated polyesters that are widely used in construction, rharine, and synthetic marble applications. Other minor applications are dyes, esters, drying oil modifiers and pharmaceutical intermediates. 

The Favorskii reaction has been used to effect ring contraction in the synthesis of strained ring compounds. Entry 4 in Scheme 10.3 illustrates this application of the reaction. With 7,7 -dihalo ketones, the rearrangement is accompanied by dehydrohalo-genation to yield an a,/ -unsaturated ester, as illustrated by entry 3 in Scheme 10.3. 

Addition poly(imide) oligomers are used as matrix resins for high performance composites based on glass-, carbon- and aramide fibers. The world wide market for advanced composites and adhesives was about 70 million in 1990. This amounted to approximately 30-40 million in resin sales. Currently, epoxy resins constitute over 90% of the matrix resin materials in advanced composites. The remaining 10% are unsaturated polyester and vinylester for the low temperature applications and cyanate esters and addition poly(imides) for high temperatures. More recently thermoplastics have become important and materials such as polyimides and poly(arylene ether) are becoming more competitive with addition polyimides. 

Allenic esters react as enoates in tandem difunctionalization reactions using organocopper reagents as Michael donors (J.-y-unsaturated esters result (equation 28).81 These substrates have found application in the synthesis of a variety of heterocyclic systems.114... 

There was only one reported example of successful RCM involving an a,(3-unsaturated ketone.17 RCM of a,fJ-unsaturated esters was known to be difficult unless special conditions, possibly not applicable to ketones (the addition of Lewis-acids), were used.1 0... 

The addition of other metals to promote skeletal catalysts has been the subject of a number of investigations including the use of V, Cr, Mn, and Cd for hydrogenation of nitro compounds [23], Cd in the hydrogenation of unsaturated esters to unsaturated alcohols [24], and Ni and Zn for the dehydrogenation of cyclo-hcxanol to cyclohexanone. The use of Cr as a promoter is particularly attractive as copper chromite catalysts arc used in a wide range of industrial applications. Lainc and co-workers [25] have made a detailed study of the structure of chromium promoted skeletal copper catalysts. 

This reaction illustrates a stereoselective preparation of (Z)-vinylic cuprates, 5 which are very useful synthetic Intermediates. They react with a variety of electrophiles such as carbon dioxide,5,6 epoxides,5,6 aldehydes,6 allylic halides,7 alkyl halides,7 and acetylenic halides 7 they undergo conjugate addition to a,6-unsaturated esters,5 6 ketones,6 aldehydes,6 and sulfones.8 Finally they add smoothly to activated triple bonds6 such as HCSC-OEt, HC3C-SEt, HC=C-CH(0Et)2. In most cases these cuprates transfer both alkenyl groups. The uses and applications of the carbocupration reaction have been reviewed recently.9 The configurational purity in the final product 1s at least 99.951 Z in the above transformations. 

The inter- and intramolecular Diels-Alder reactions of furans, and their applications to the synthesis of natural products as well as synthetic materials, were reviewed <1997T14179>. HfCU promoted the endo-seXccuve. inter-molecular Diels-Alder cycloadditions of furans with a,/3-unsaturated esters <2002AGE4079>. The cycloaddition between furan and methacrylate was also achieved under these conditions, providing, however the o-isomer as the major cycloadduct. A catalytic enantioselective Diels-Alder reaction between furan and acryloyl oxazolidinone to provide the < 46i-adduct in 97% ee was achieved by using the cationic bis(4-fer7-butyloxazoline)copper(ll) complex 55, as shown in Equation (41) <1997TL57>. 

Metathesis of olefins, through the use of transition metal catalysis, is an important application in the petrochemical as well as in the polymer chemical industry for the production of special olefins and polymers (cf. Section 2.3.3). This chemistry is also applicable to unsaturated fatty acid esters, such as acetic acid methyl ester. However, the high price and unsustainability of the catalysts, compared with the fatty acids as substrates, have made commercial utilization not yet possible nevertheless they are of great interest for researchers in this field. 

Complementary selectivity is observed when the reaction is carried out at low temperature with KH in THF in the presence of 18-crown-6 ether. With the use of n-BuLi in DME at low temperature, the yields of oc-(trimethylsilyl)methyl-a,P-unsaturated esters are roughly comparable to those obtained in standard conditions (NaH, THF, room temperature). Other modified Homer-Wadsworth-Emmons reaction procedures proved to be applicable. For example, addition of two equivalents of an aqueous solution of K2CO3 and formaldehyde to diethyl 2-(trimethylsilyl)-l-(ethoxycarbonyl)ethylphosphonate gives ethyl a-(trimethylsilyl)methyl acrylate in 48% yield. ... 

Yastrebova in 1970, the use of dialkyl l-(alkoxycarbonyl)methylphosphonates in Homer-Wadsworth-Emmons reactions has carefully been covered in several exhaustive and excellent reviews.All the factors governing the reaction (nature of the carbanion and carbonyl group, reaction conditions, mechanism, and stereochemistry) have been studied in depth. We invite the reader to refer to these papers. We discuss here the synthetic applications resulting directly from the use of dialkyl l-(alkoxycarbonyl)methylphosphonates, which is the pathway of choice for the preparation of a,P-unsaturated alcohols and related compounds via the a,P-unsaturated esters. 

Ethenolysis of unsaturated esters results in the synthesis of shorter-chain w-unsaturated esters, compounds with a broad range of application. Excess ethene can easily be used (e. g. by use of ethene pressures of 30-50 bar) to suppress self-metathesis of the ester and to force the conversion to completion. Ethenolysis of methyl oleate produces methyl 9-decenoate and 1-decene (Eq. 13) [37,38]. High conversion of methyl oleate can be obtained at room temperature by use of a Re207 catalyst promoted with tetraalkyltin. 

Nevertheless only scare data is available in the recent literature on the application of Group VIII noble metal (M) or rhenium-based mono- and Re-M bimetallic catalysts, in the hydrogenolysis of esters or hydrogenation of acids to alcohols. Recently a few publications, - and patents. have been reported on the transformation of different carbonyl compounds (saturated and unsaturated esters, acids and carboxamides) over rhenium-containing catalysts. In the bimetallic catalysts used for the hydrogenation of carbonyl compounds the rhenium was combined with Pd, or Rh. In the case of catalysts used for the hydrogenation of unsaturated carbonyl compounds the rhenium is usually modified with tin. ... 

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