Ethoxy vinyl esters

G. Asymmetric Pummerer Rearrangement Induced by Ethoxy Vinyl Esters... 

Pummerer rearrangement of the optically active sulfoxide (64) to the 1,3-benzoxathiinone (65) occurs with moderate to good transfer of enantiomeric excess when the reaction is promoted by ethoxy vinyl esters <97TA303>. 

Currently, enol esters (1, ethoxjwinyl 5, vinyl and 6, isopropenyl esters Fig. 12) are the most useful irreversible acyl donors, because the liberated alcohol then is an enol that rapidly tautomerizes as shown in Figure 13. Economical vinyl acetate in particular is often favored, although acetaldehyde obtained can form an imine with free amino groups of the enzyme and lead to catalyst inhibition. In this sense, ethoxy vinyl esters, still rarely used acyl donors, are interesting, because they leave an alcohol that tautomerizes into harmless ethyl acetate (19). 

Kita et al. have reported an asymmetric Pummerer rearrangement of optically active sulphoxides, induced by ethoxy vinyl esters (EVE). In particular ethoxy vinyl acetate 50 was used to effect the Pummerer rearrangement of sulfoxides 51a-b in good yields and high enantioselectivity. 

Zinc salts function as elfective catalysts in the conversion of 1-ethoxy-vinyl esters (83) into jS-ketoester enol esters (84) the starting esters are readily obtained by mercury-catalysed addition of carboxylic acids to ethoxyacetyl-ene. This rearrangement is most effective with the esters of weak acids, whereas an analogous thermal reaction functions best with esters of strong acids. 

Acetic acid, nitro-, methyl ester, 55, 77, 78 Acetic acid, trifluoro-, 55 70 Acetonitrile, diphenyl-, 55, 94, 102 Acetonitrile, diphenyl-2-(l-ethoxyethenyl)-[ Acetonitrile, diphenyl-2-(l-ethoxy-vinyl)-, 55, 102... 

The esters, 7-ethoxycyclopropyl acetate (7 a) and benzoate (7b) have been synthesized by the addition of the Simmons-Smith reagent 22> to 1-ethoxy vinyl acetate and benzoate, respectively.4) A potential difficulty in this reaction lies in the fact that zinc iodide, a Lewis acid, is generated in the process and may induce cyclopropane ring opening (Section 4.3.3). However, when glyme is used as a solvent, the acid-labile bonds remain intact since the zinc salt is insoluble in this medium.23)... 

C esters at an ortho position i ethoxy(vinyl)silane in the presence o r ect.s of substituents on this insertion... 

Synthesis of acetic acid 2-[2-(4-vinyl-phenoxy)-ethoxy]-ethyl ester (6)... 

Octylstyrene (4) and poly(4-octylstyrMie) (10) together with 4-acetox) tyrene (3) were polymerized in substance for 20h to 30h at 123°C. The polymerization of poly(4-octylstyrene) (10) wifli the monomer acetic acid 2-[2-(4-vinyl-phenoxy)-ethoxy]-ethyl ester (6) was carried out in diglyme over five days at... 

However, most asymmetric 1,3-dipolar cycloaddition reactions of nitrile oxides with alkenes are carried out without Lewis acids as catalysts using either chiral alkenes or chiral auxiliary compounds (with achiral alkenes). Diverse chiral alkenes are in use, such as camphor-derived chiral N-acryloylhydrazide (195), C2-symmetric l,3-diacryloyl-2,2-dimethyl-4,5-diphenylimidazolidine, chiral 3-acryloyl-2,2-dimethyl-4-phenyloxazolidine (196, 197), sugar-based ethenyl ethers (198), acrylic esters (199, 200), C-bonded vinyl-substituted sugar (201), chirally modified vinylboronic ester derived from D-( + )-mannitol (202), (l/ )-menthyl vinyl ether (203), chiral derivatives of vinylacetic acid (204), ( )-l-ethoxy-3-fluoroalkyl-3-hydroxy-4-(4-methylphenylsulfinyl)but-1 -enes (205), enantiopure Y-oxygenated-a,P-unsaturated phenyl sulfones (206), chiral (a-oxyallyl)silanes (207), and (S )-but-3-ene-1,2-diol derivatives (208). As a chiral auxiliary, diisopropyl (i ,i )-tartrate (209, 210) has been very popular. 

Metallated 1-ethoxy-1,3-dienes 697 and 712, obtained from the corresponding acetals by means of the LICKOR base, have been treated with alkyl halides, epoxides, carbonyl compounds, carbon dioxide and carboxylic esters affording ( )-l-substituted 1-ethoxy-1,3-dienes and, after hydrolysis, a,P-unsaturated carbonyl compounds1007-1010 (Scheme 186). Intermediates 697 and 712 have been transformed into the corresponding vinyl stan-nanes, which were submitted to Stille couplings with iodobenzene and benzoyl chloride823. 

Displacement of an ethoxy attached to a vinylic side-chain occurs in mineral acid at ambient temperature with concurrent formation of a C—C bond [2042]. Ethereal hydrogen chloride annulates nitro and side-chain epoxide groups intramolecular reduction-oxidation leads to the 4-quinolinone in high yields [2314]. A C—N bond is formed when a methylthiovinylpyrrole is treated with a strong base and a malonic ester. Lactim ethers such as 5-methoxy-2 -pyrrole condense with acetonedicarboxylate in a base-induced cyclization at room temperature [3258]. 

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