Synthesis of Enol Esters

Addition of Carboxylic Acids Synthesis of Enol Esters... 

Synthesis of Enol Esters - Typical Experiment - (Z)-3-Methylbuta-l,3-dien-l-yl benzoate [9]... 

The above results show that the ruthenium-catalyzed activation of alkynes towards nucleophiles has first led to classical electrophilic activation, leading to Markovnikov additions as observed for addition of carboxylic acids and the synthesis of enol esters. In 1986, the regioselective anfi-Markovnikov addition of in-situ-generated... 

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. ... 

Scheme 4 Synthesis of enol esters through Ru vinylidenes...

Dimethyldioxirane DMDO discovered by Murray and coworkers, is a superior choice for the epoxidation of most olefins, giving comparable or higher yields than m-CPBA-based epoxidation [21]. Proceeding rapidly under neutral and mild conditions, it is especially well suited for the synthesis of sensitive epoxides of enol esters, enol lactones [22], and enol ethers [23]. The reaction is stereospecific, gen-... 

Scheme 2.22 Synthesis of/ -allenic esters 65 by 1,6-cuprate addition to 2-en-4-ynoates 64 and regioselective enolate protonation.

THE SYNTHESIS OF ENOL ETHERS BY METHYLENATION OF ESTER 1-PHENOXY-1-PHENYLETHENE AND 3.4-DIHYDRO-2-METHYLENE-2H-1-BENZOPYRAN... 

Very recently, new ruthenium catalysts, for example RuCl2(triazol-5-ylidene) (p-cymene) [11] and the catalytic system generated in situ from [RuCl2(p-cym-ene)]2, tris(p-chlorophenyl)phosphine, and 4-dimethylaminopyridine [12], have provided efficient catalysts for synthesis of the same type of enol ester. The regio-selective cyclization of acetylenic acids containing a terminal triple bond to give unsaturated lactones was performed in the presence of catalytic amounts of Ru(tris(pyrazolyl)borate)(PhC=C(Ph)C CPh)(PMe2iPr2) [13],... 

B. Synthesis of Enolates from Enol Ethers and Esters. 542... 

The rDA route to isopropenyl acetoacetate and to vinyl acetoacetate was apparently the first synthesis of acetoacetate esters of enols. The reaction between diketene (26) and norbomenols (25a) and (25b) generated the protected ethylene cycloadducts (27), which upon FVP gave the desired isopropenyl acetoacetate (28a) in 48% yield and vinyl acetoacetate (28b) in 61% yield (equation 20). ... 

Pine, S. H., Kim, G., Lee, V. The synthesis of enol ethers by methylenation of esters 1-phenoxy-1-phenylethene and 3,4-dihydro-2-methylene-2H-1-benzopyran. Org. Synth. 1990, 69, 72-79. 

Corey and Wright have utilized reductive conversion of a vinyl diethyl phosphate (73) to an alkene 74 in a synthesis of colneleic ester via the enol esters 72.43... 

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