Olefinic esters preparation

A unique approach to the requisite C-ring fragment 51 is achieved through reductive cyclization of olefinic ester 55 by way of the titanium alkylidene, as described by Rainer and Nicolaou [59]. The olefinic ester 55 is prepared in ten steps from (R)-isobutyl lactate using consecutive chelation-controlled... 

The esters prepared by the direct esterification of olefins were designed, as we mentioned at the outset, for potential use as plasticizers for PVC resin. Several... 

The aluminum alkoxide mixture or "oxidized growth product is fed to a series of vacuum flash evaporators to remove solvent introduced earlier in the triethylaluminum preparation. This vacuum stripping step also removes olefins formed during the growth reaction and the myriad of by-products formed during oxidation (14) Efficiency of this stripping process is a key factor in alcohol product quality. This is the opportunity to separate volatile impurities—olefins, esters, aldehydes, paraffins, etc.—from product alcohols while the alcohols are in a nonvolatile form (aluminum alkoxides). 

Fig. 11.7. trans-Selective Wittig olefination of aldehydes I—Preparation of a trans-configured a,j8-unsaturated ester (preparation of the starting material Figure 17.24). 

The key intermediate for the construction of the dioxacyclopentane moiety was the diol 247 which has been synthesized from the rrans-olefinic ester 242. This olefinic ester had been used by the same research group for synthesis of other prostanoids published 1972118>. The preparation of 246 had been performed by reaction... 

Olefinic esters may be obtained directly by the Knoevenagel reaction. Alkyl hydrogen malonates are used in place of malonic acid. Decarboxylation then gives the ester directly as in the preparation of ethyl 2-heptenoate (78%) and methyl m-nitrocinnamate (87%). Alkyl hydrogen malonates are readily available by partial hydrolysis of dialkyl malonates. The use of malonic ester in the condensation leads to olefinic diesters, namely, alkylidenemalonates such as ethyl heptylidenemalonate (68%). A small amount of organic acid is added to the amine catalyst since the salts rather than the free amines have been shown to be the catalysts in condensations of this type. Various catalysts have been studied in the preparation of diethyl methylenemalonate. Increased yields are obtained in the presence of copper salts. Trimethylacetalde-hyde and malonic ester are condensed by acetic anhydride and zinc chloride. Acetic anhydride is also used for the condensation of furfural and malonic ester to furfurylidenemalonic ester (82%). ... 

Certain aromatic and heterocyclic olefinic esters ate best prepared by condensation of ethyl acetate and aromatic aldehydes by sodium sand (Claisen). Benzaldehyde in this reaction gives ethyl cinnamate, C,HsCH=CHC03C,H5 (74%). p-Methylbenzaldehyde, furfural, furylactolein, and 2-thiophenecarboxaldehyde have been condensed in a similar manner. 

Olefinic alcohols are best prepared by the action of lithium aluminum hydride on the corresponding acid or ester as in the preparation of 3-penten-l-ol (75%). The double bond may be in the a,/S-position to the ester group, The Bouveault-Blanc procedure has also been used with success for reduction of nonconjugated olefinic esters. The addition of the sodium to an alcoholic solution of the ester is superior to the reverse addition of. the ester to sodium in toluene for the preparation of 2,2-dimethyl-3-buten-l-ol (62%). Selective catalytic hydrogenation is inferior. Large amounts of catalyst are required, and the products contain saturated alcohols. ... 

Mild conditions should be employed in alkaline hydrolysis of olefinic esters. Double bonds in many acids migrate readily during saponification. Aqueous alcoholic sodium hydroxide is used in the preparations of 3-ethyl-3-pentenoic acid (56%) and /S-methylcinnamic acid (41%). ... 

Catalytic hydrogenation of the olefinic esters obtained in the Knoeve-nagel and Stobbe condensations (method 37) is valuable for the preparation of alkylmalonates and alkylsuccinates, particularly for those having branching in the alkyl group. 

The di-O-tosylates (prepared by action of tosyl chloride in pyridine) are reduced with zinc (Nal/Zn route e Tipson-Cohen reaction) [13]. Cyclic ortho-esters (prepared by reaction of the diol with ethyl orthoformate) are transformed into olefins by simple heating in the presence of acids (Eastwood reaction, route b) [14]. Cyclic thiocarbonates (obtained by reaction of a diol with thiophosgene or (V,(V -thiocarbonyl-di-imidazole) are reduced to olefin with trimethyl phosphite (Corey-Winter method, route c) [15]. Finally, reduction of vicinal di-xanthates with tri- -butyltin hydride according to the Barton procedure [16] affords olefins via a reductive elimination process route a). The Corey-Winter, Garegg, and Tipson-Cohen methods are most commonly applied for deoxygenation of sugar diols. 

The methyl ester of corydalic acid (413) can be isolated from Covydalis incisa when the plant is in the vegetative stage and can be classed as a secobenzophenanthridine alkaloid (G. Nonaka, T. Kodera and I. Nishioka, Chem.Pharm.Bull., 1973, 21, 1020). It has been synthesised by the condensation of the acid anhydride (410) with the imine (411) to give an acid that is decarboxylated to a mixture of geometrical isomers, of which (412) is hydrolysed, esterified and reduced to ( )-meth-y1 corydalate (413) (Cushman and W.C. Wong, J.org.Chem., 1984, 49, 1278). It has also been prepared by the reduction, oxidation and esterification of the olefin (414), prepared from the berberine alkaloid corysamine (Hanaoka, S. Yoshida and C. Mukai, Chem.Comm., 1984, 1703). 

Petrova, J., Coutrot, P, Dreux, M.. and Savignac. P. The a-chlorination and carbonyl olefination. Arylchloromethanephosphonic acid esters. Preparation, alkylation, and Wittig-Homer reactions. Synthesis, 658, 1975. 

For the preparation of the 10-ethyl-10-deaza analogues rac,L-(IV.108), cf,L-(IV.108), and /,l-(IV.108), a somewhat different scheme was followed to form the required racemic or optically active acid ester (IV.114) [124], The dilithium salt of 4- -propylbenzoic acid was condensed with allyl bromide, and the resulting acid was esterified with MeOH-HCl to obtain the olefinic ester, (IV.115). On oxidation with Ru02-NaI04, (IV.115) yielded (IV.114) (77%). Resolution of (IV.l 14) was achieved efficiently with J-(l-phenylethyl)amine. The remaining steps from (IV.l 14) to (IV. 108) were the same as those used to form the 10-methyl-10-deaza analogue, (IV.107). 

Scheme 3 Olefin (29) prepared from dienone (26) by standard organic reactions was converted to bromohydrin derivative (30), which on subjection to photolysis and dehydrohalogenation yielded ketal (32), whose conversion to a,P unsaturated ketone (34) was accomplished by hydrolysis, bromination and dehydrobromination respectively. The cyanation of (34) followed by hydrolysis and esterification produced ester (35), which on Clemmensen reduction and oxidation afforded lactone (37). Reduction of (37) followed by oxidation and esterification gave ketoester (38), which was converted to (39).

Olefins. The reaction of tertiary a-chloroboronic esters (preparation, 5, 201) with silver nitrate in aqueous ethanol at 25 results in formation of olefins in good yield. For example, (1) is converted into cyclohexylidenecyclo-hexane (2) in 83% yield, and (3) is converted into (4). 

A novel insoluble green complex of palladium(II) and N,N -salicylideneethylenedi-amine (salen) functions as a selective heterogeneous catalyst, notably for the reduction of alkynes in the presence of alkenes, and of the latter in the presence of certain functional groups. E ciVEthylene from acetylene derivs. A soln. of startg. acetylene deriv. in EtOH hydrogenated for 17 min in the presence of the palladium(ll) complex (prepared from potassium tetrachloropalladate, salen, and triethylamine) cis-product. Y 100%. Reduction of alkenes is considerably slower however, terminal olefins may be reduced in the presence of internal olefins esters, oxo compds., dibenzyl ether, and iodobenzene were unaffected. F.e., also ar. amines from nitro compds. s. J.M. Kerr et al.. Tetrahedron Letters 29, 5545-48 (1988). 

The diazo reaction with olefins as shown previously is still the fastest method to get hold of mixtures of diastereomers, often, however, with moderate yields due to the lack of reactivity of the olefins. Several nor-chrysanthemic esters [479], alkoxycyclopro-pane carboxylic esters [480,481], which are interesting because of their photostabihty and insecticidal activity [482], and 2,2,3,3-tetramethylcarboxyhc ester [483] were prepared by this route. Asymmetric synthesis using optically active iron carbonyl-olefin complexes afforded 1-R-configurated esters, i.e. precursors for caronaldehyde [484]. The addition of diazopropane across the double bond of olefinic esters via pyrazolines [485, 486] also provides a rapid access to sometimes more complex cyclopropane carboxylic esters with questionable purity, from which the pure compounds can be separated. 

Pyridinium chlorochromate (PCC) oxidizes trialkylboranes (prepared from terminal olefins and diborane) directly to aldehydes in high yield, presumably via the corresponding borate ester (1) borate esters, prepared by two alternative routes from alcohols, are oxidized in high yield to aldehydes and ketones using the same reagent (Scheme 1). ... 

The conversion of acetylenes into olefinic esters by use of addition reactions has been illustrated by the following two examples, (i) 1-Alkenyl boranes, which are readily prepared by the hydroboration of alkynes, are converted into a,fi-unsaturated carboxylic esters in good yield by reaction with carbon monoxide in the presence of palladium chloride and sodium acetate in methanol the process is carried out at atmospheric pressure and occurs with retention of configuration with respect to the alkenyl borane. (ii) Carboxylic acids add to acetylenes in the presence of silver carbonate to provide a novel synthesis of enol esters, which are formed in an 8 2 mixture of isomers. ... 

Poly (olefin-ester) multiblock copolymers belong to a quite new and fast developing class of polyester elastomers [58-60]. The copolymer with PBT rigid segments and flexible polyisobutylene (PIB) segments was prepared by polycondensation in the molten state with DMT, BD, and functionalized PIB, in the presence of titanium tetrabutoxide as catalyst. a,o -Dianhydride [58] and dihydroxyl-terminated PIB of molecular weights 1000, 2200, 4800, and 10000 g/mole were used (Schemes 17 and 18). A multiblock copolymer with PBT and... 

The aminolysis of esters has been used widely for the preparation of amides. Water and certain solvents, such as glycols, promote the reaction [11], although the presence of glycols may interfere with the isolation of amides at times. In the case of olefinic esters, addition of amine to the double bond also takes place during aminolysis, an example of the Michael condensation. 

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