Of unsaturated ester

The cycloaddition reactions of unsaturated esters with cyclopentadiene on y-alumina [18]... 

Conjugate reductions and conjugate alkylations of unsaturated esters are found in Section 74 (Alkyls from Alkenes). 

Branched-regioselective hydroformylation of unsaturated esters has been achieved [41]. The use of the phosphaadamantane ligand 1, which is readily available from acetylacetone and phenylphosphine (Eq. 1), proved particularly useful in terms of reaction rate, regio-, and chemoselectivity [42-44]. 

A facile synthesis of cyclic five-, six-, and seven-membered oxonitriles 7-35 by a combination of an ozono lysis and an aldol reaction has been described by the Fleming group [17]. As starting material the unsaturated oxonitriles 7-33 are used, which are easily accessible by reaction of unsaturated esters 7-32 with LiCHjCN (Scheme 7.11). It can be assumed that 7-34 acts as an intermediate. 

Scheme 21 Cathodic cyclization of unsaturated esters yield (alcohol) 60%, yield (TMS ether) 67%.

Herein we will focus on the recent development of vinylogous [1] aldol reactions and their application in the synthesis of natural products [2-5]. In particular the synthesis of unsaturated esters through the vinylogous Mukaiyama aldol reaction is of great interest, since it provides rapid access to larger carbon frameworks and allows for a wide variety of transformations of the double bond (dihydroxylation, epoxidation, cuprate addition etc.). 

Nickel-cyclam and related complexes can also be used though previous reports indicated that the turnover of Ni/(tet a) in acetonitrile is low [85]. The process has now been reinvestigated to show that Ni/(tet a) can been used in catalytic conditions (2%) in DMF containing NH4CIO4 as proton source to perform the alkylation of unsaturated esters, ketones, or nitriles (Table 9) [86]. Yields are good if the terminal carbon of the double bond is not substituted (Ri = H). 

The reduction of unsaturated esters encompasses the reduction of esters containing double and triple bonds, usually in positions, and/or aromatic rings. Such esters may be converted to less saturated or completely saturated esters, to unsaturated or less unsaturated alcohols or to saturated alcohols. Presence of aromatic rings in conjugation with the multiple bonds facilitates saturation of the bonds. Aromatic rings are hydrogenated only after the saturation of the double bonds. 

Complete reduction of unsaturated esters to sativated alcohols takes place when the esters are hydrogenated over Raney nickel at 50° and 150-200 atm [44] or over copper chromite at temperatures of 250-300° and pressures of 300-3 50 atm [52,1056] (p. 153). In contrast to most examples in the literature the reduction of ethyl oleate was achieved at atmospheric pressure and 270-280° over copper chromite, giving 80-90% yield of octadecanol [1074]. a.,P-Unsaturated lactones are reduced to saturated ethers or alcohols, depending... 

When R2 substituent is flourocontaining alkyl group, the transformation 17 18 becomes hindered and its proceeding requires some special methods. For example, in [48] Biginelli-like cyclocondensations based on three-component treatment of 3-amino-l,2,4-triazole or 5-aminotetrazole with aldehydes and fluorinated 1,3-dicarbonyl compounds were investigated. It was shown that the reaction can directly lead to dihydroazolopyrimidines 20, but in the most cases intermediate tetrahydroderivatives 19 were obtained (Scheme 10). To carry out dehydration reaction, refluxing of tetrahydroderivatives 19 in toluene in the presence of p-TSA with removal of the liberated water by azeotropic distillation was used. The same situation was observed for the linear reaction proceeding via the formation of unsaturated esters 21. 

Chen and co-authors in their work [50] offered key stages for mechanism of heterocyclization leading to compounds 25 and 26 (Scheme 12). The reaction sequence for azolopyrimidines 25 formation is very similar to that published in [47] and presented in Scheme 9. Pathway to tetrahydroderivatives 26, in opinion of [50], also includes at the beginning Knoeveganel condensation. Further step of the reaction in this case should be the addition of exocyclic NH2 group of aminoazole to enone fragment of unsaturated ester, with subsequent cyclization of the adduct formed into final tetrahydropyrimidine (Scheme 14). 

Reactions of unsaturated esters with electron-rich alkenes have been reported to yield only cyclobutane derivatives. However, NMR examination of the products has indicated the formation of substituted 3,4-dihydro-2H-pyrans. The most informative feature of the spectra is the C-2 proton coupling constants of ca. 3 Hz with the two different protons at... 

The reduction of unsaturated esters has, until recently, proved rather more difficult to reduce in high yield and selectivity, possibly due in part to their inferior donor properties... 

The success of the reaction is crucially dependent on the cleanliness of the zinc surface, prior to the formation of the organozinc reagent sonication has been suggested as a valuable aid to this reaction (cf. Expt 7.14). Under standard conditions, the hydroxy ester is the major product when the reaction is carried out in ether or benzene the contaminants which frequently arise during distillation are the a,0- and 0,y-unsaturated esters. Dehydration can be deliberately effected with the aid of reagents such as fused potassium hydrogen sulphate or acetic anhydride. Catalytic hydrogenation of the mixture of unsaturated esters fol-... 

Jimenez-Rodriguez C, Eastham GR, Cole-Hamilton DJ (2005) Dicarboxylic acid esters from the carbonylation of unsaturated esters under mild conditions. Inorg Chem Commun 8(10) 878-881... 

In the reaction of "carbomethoxypalladium salts with olefins, there is a marked tendency to product unsaturated esters in which the double bond is not conjugated with the carbonyl. The reaction of carbomethoxy palladium acetate with a-methylstyrene produced an 86% yield of unsaturated esters of which 96% was the non-conjugated isomer, methyl 3-phenyl-3-butenoate and only 4% was the imws-conjugated product 24>. 

This four-component reaction represents a straightforward method for the preparation of unsaturated esters and amides [156-159]. The system Pd(OAc)2/SIPr HC1 has been reported to efficiently catalyze the coupling of diazonium salts with boronic acids in the presence of CO and ammonia [160] to yield the corresponding amides in good yields (Scheme 17). 

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. 

RECOVERIES OF UNSATURATED ESTERS AFTER TREATMENT OF METHYL ESTERS FOR 90 MIN AT 100°C WITH METHANOLIC BF3, HC1 OR H2S04 (51... 

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