Olefinic ester

Copolymers Containing Ethylene 277 Table 11.12 Typical properties of three olefin-ester copolymers... 

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... 

Boelhouwer s discovery (23) prompted a flurry of activity in this area. Baker applied the Boelhouwer catalyst to the metathesis of w-olefinic esters (88). At an ester/W molar ratio of 20/1 (68°C), symmetrical olefinic diesters were formed in 34-36% yields with concomitant elimination of ethylene. In addition, Baker identified products recovered in 3-8% yield corresponding to addition of HC1 across the terminal double bond. 

The first example of a heterogeneous catalyst able to metathesize olefinic esters was recently reported (92). The combination of Re207/ (CH3)4Sn at an olefin/Re/Sn molar ratio of 219/6/1 converted methyl 4-pentenoate at 50°C in 51% conversion to ethylene and the corresponding dimethyl ester of 4-octene-l,8-dioic acid. This reaction exhibited a high degree of selectivity (>99%), and in the absence of (CH3)4Sn the rhenium catalyst was inactive (90). 

Recently, Nicolaou and coworkers have devised a novel, one-pot strategy for the direct transformation of acyclic olefinic esters to cyclic enol ethers [34]. Unlike the molybdenum alkylidene 1 (see Sect. 3.2), initial reaction between the Tebbe reagent 93 and an olefinic ester results in rapid carbonyl olefination to afford a diene intermediate. Subsequent heating initiates RCM to afford the desired cyclic product (Scheme 17). 

Scheme 17. Titanium-mediated metathesis strategy for the conversion of olefinic esters (118) to cyclic enol ethers (123) (Nicolaou et al.) [34]...

Scheme 18. The conversion of olefinic ester 125 to cyclic enol ether 127. (a) 4.0 equiv of Tebbe reagent (93), 25°C, 20 min then reflux, 5 h, 71% (b) 1.3 equiv of Tebbe reagent (93), 25°C, 20 min, 77% (c) 2.0 equiv of Tebbe reagent (93), 25°C, 20 min then reflux, 3 h, 65% (Nicolaou et al.) [34a]...

Preliminary investigations in this area involved treatment of olefinic ester 125 with a large excess (4 equiv) of the Tebbe reagent 93 (Scheme 18) [34a]. After 20 min at 25°C, the mixture was heated at reflux for 5 h. This resulted in the formation of tricyclic enol ether 127 in 71% overall yield. If only 1.3 equiv of Tebbe reagent 93 was employed and the reaction stopped after 20 min at 25°C,the olefinic enol ether 126 could be isolated in 77% yield. The proposed intermediacy of diene 126 in the initial tandem sequence was validated by its subsequent conversion into the cyclic enol ether 127 under the original reaction conditions [34a],... 

The anion radical species formed by the electroreduction of aliphatic esters show interesting reactivities, and the reduction of olefinic esters gives bicyclic products with high regio- and stereoselectivity. The electroreduction of the ester in the presence of chlorotrimethylsilane affords a tricyclic product (Scheme 21) [35, 40]. The mechanism of this cyclization reaction seems to be the addition of anion radical species, formed by the reduction of the ester group, to the carbon-carbon double bond. 

Conclusive evidence for the participation of 7r-allylic intermediates in double bond migration has been obtained from a study of the nickel-catalysed hydrogenation of the isomeric olefinic esters methyl oleate and methyl elaidate using tritium as a tracer [147]. It was also concluded that in this system cis—trans isomerisation occurred by an addition—abstraction mechanism. 

T he oxidation of olefins by selenium dioxide has received much atten-- tion because of the unique characteristics of the reaction that produces an allylic derivative of the olefin (ester, alcohol, or ether, depending upon the solvent) and elemental selenium as the final reduced state of the oxidant. 

A variety of barium sulfonates have found use in antifriction lubricants for high speed bearing applications. Calcium and sodium salts of sulfonated olefins, esters, or oils are used for the enhancement of extreme pressure properties of grease and gear lubricants,... 

In another study, Buchanan and McLay (104) found that the equatorial oicy- ri clic ketotosylate 36S gave the seven-membered olefinic ester 367 while the,. axial isomeric tosylate 368 gave the seven-membered olefinic ester 371. Again, the reaction of the equatorial tosylate occurs through the fragmen- tation of intermediate 366. The transformation 368- 371 can be explained by the stereoelectronically controlled retro-Dieckmann fragmentation of 369 followed by the elimination of the tosylate group from 370. 

It has been reported (102) that the equatorial bicyclic ketotosylate 360 (R=CH3) is transformed into monocyclic olefin ester 362 (R=CH3) by treatment with sodium ethoxide while the axial isomer 363 yielded the bicyclic olefin 364. Similarly, compound 360 (R=C00CH3) gave 362 (R=C00CH3 ) (103). Thus, reactions with the equatorial tosylates take place via the stereoelectroni-cally controlled fragmentation of intermediate 361 (R=CH3 or COOC2H5). 

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). 

The nickel and palladium compounds described above are useful in processes for polymerising various olefins, and optionally also for copolymerising olefinic esters, carboxylic acids or other functional olefins with these olefins. When (I) is used as a catalyst, a neutral Lewis acid or a cationic Lewis or Bronsted acid whose counterion is a weakly coordinating anion is also present as part of the catalyst system. The neutral Lewis acid is originally uncharged (i.e. not ionic). Suitable neutral Lewis acids include SbFs, A B and BF3. By a cationic Lewis acid is meant a cation with a positive charge such as Ag+, H+ and Na+. 

Isopropyl anisole (171) was converted to bromide (172) by metalation, formylation and bromination. Alkylation with cyclopropyl ketoester produced (173) whose transformation to alcohol (174) was achieved by saponification, decarboxylation and reduction.. Its conversion to homoallylic bromide (175) was accomplished by the method of Julia et al. [56]. Alkylation of ethyl acetoacetate with bromide (175) furnished p-ketoester (176). It was subjected to cyclization with stannic chloride in dichloromethane. The resulting tricyclic alcohol provided the olefinic ester (177) by treatment with mesylchloride and triethylamine. Epoxidation followed by elimination led to the previously reported intermediate (146) whose conversion to triptolide (149) has already been described. 

Also via Hydroxy acids (Section 313) Olefinic amides (Section 349) Olefinic esters (Section 362) Olefinic nitriles (Section 376). 

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... 

It was found in the early alkylation work that various olefin esters could be used in place of olefins to alkylate isobutane with a strong H2SO4 catalyst. It was also known that diethyl sulfate was an accepted ethylating agent in the chemical industry. 

Several papers on the chemistry of longifolene derivatives have been published. These include the conversion of the two half-esters (225) and (226) into the same olefinic ester (227) with Pb(OAc)4-Cu(OAc)2, the reaction of longifolene (228) with mercuric acetate followed by iodine chloride to give (229) and (230), and the reaction of longicyclene (231) with bromine in pyridine and iodine chloride-pyridine complex in acetic acid to yield (232) and (233) respectively. 

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