Hydroxy ethyl vinyl ether

The protected indanone 109 was obtained by the Pd-catalyzed one-pot reaction of the triflate of salicylic aldehyde 108 with 2-hydroxy ethyl vinyl ether and addition of AcOH [65], In this case, selective a-arylation is followed by annulation promoted by Pd and AcOH to give 109. 

Simple alkyl radicals such as methyl are considered to be nonnucleophilic. Methyl radicals are somewhat more reactive toward alkenes bearing electron-withdrawing substituents than towards those with electron-releasing substituents. However, much of this effect can be attributed to the stabilizing effect that these substiments have on the product radical. There is a strong correlation of reaction rate with the overall exothermicity of the reaction. Hydroxymethyl and 2-hydroxy-2-propyl radicals show nucleophilic character. The hydroxymethyl radical shows a slightly enhanced reactivity toward acrylonitrile and acrolein, but a sharply decreased reactivity toward ethyl vinyl ether. Table 12.9 gives some of the reactivity data. 

Ethyl vinyl ether is also useful for hydroxy group protection. The resulting derivative (1-ethoxyethyl ether) is abbreviated as the EE group.156 As with the THP group, the EE group introduces an additional stereogenic center. 

This procedure consists of the synthesis of a precursor, methoxymethyl vinyl ether, an a-hydroxy enol ether, and the intramolecular hydrosilylatlon of the latter followed by oxidative cleavage of the silicon-carbon bonds. The first step, methoxymethylation of 2-bromoethanol, is based on Fujita s method.7 The second and third steps are modifications of results reported by McDougal and his co-workers. Dehydrobromination of 2-bromoethyl methoxymethyl ether to methoxymethyl vinyl ether was achieved most efficiently with potassium hydroxide pellets -9 rather than with potassium tert-butoxide as originally reported for dehydrobromination of the tetrahydropyranyl analog.10 Potassium tert-butoxide was effective for the dehydrobromination, but formed an adduct of tert-butyl alcohol with the vinyl ether as a by-product in substantial amounts. Methoxymethyl vinyl ether is lithiated efficiently with sec-butyllithium in THF and, somewhat less efficiently, with n-butyllithium in tetrahydrofuran. Since lithiation of simple vinyl ethers such as ethyl vinyl ether requires tert-butyllithium,11 metalation may be assisted by the methoxymethoxy group in the present case. 

Methyl-4-hexenal138 86 g (1,00 mol) 3-Hydroxy-3-methyl-l-buten und 150 g (2,10 mol) Ethyl-vinyl-ether werden zusammen mit 0,5 g (0,5 mol-%) Phosphorsaure im 400-m/-Druckgefa8 unter 6 atm. (600 kPa) Stick-stoff 2 Stdn. auf 150° erwarmt. Dann wird auf 20° gekiihlt und das Gemisch mit 2 ml Triethylamin neutralisiert. 

Ethyl-vinyl-ether + 3-Hydroxy-2,3-dimethyl-buten... 

Ethyl-vinyl-ether + 1-Hydroxy-1-vinyl-cyclohexan... 

The Ci9 conjugated aldehyde component was reacted with the lithium derivative of this Cg acetal in ammonia to afford an hydroxy compound which was dehydrated under mild acidic conditions to the fully conjugated C25 substance. Chain extension with ethyl vinyl ether in the presence of boron trifluoride-zinc chloride and mild acidic deethanolation gave the Cjt acetal which was then converted with prop-1-enyl ethyl ether under the same conditions to the required C30 structure of dehydro-p-apocarotenal. Lindlar partial reduction followed by isomerisation afforded the final product. The route is shown in Scheme 14b Scheme 14b... 

The reaction of pristinamycin 11 with excess ethyl vinyl ether proceeds under mild acidic catalytic conditions resulting in an essentially quantitative conversion to the acetal (54). Treatment of the acetal with aqueous acetic acid was shown to regenerate pristinamycin 11 almost quantitatively, thus providing an alternative method for the masking of the allylic hydroxy function. 

DIELS-ALDER DIENOPHILES Bis(2,2,2-trichloroethyl) azodicarboxylate. 1-Bromo-2-chlorocyclopropene. Chromium carbene complexes. (R)-Ethyl p-tolysulfinyl-methylenepropionate.l (S)-a-Hydroxy-p,p-dimethylpropyl vinyl iketone. (IR)-m-3-Hydroxy isobomyl ndopentyl ether. Oxa-zolidones, chiral. Phdnylselenenyl ben-zenesulfonate. 

Materials. VEC was prepared by the catalyzed addition of CO2 to 3,4-epoxy-l-butene using conditions typical of that used industrially [77], then purified by vacuum distillation. Other raw materials were used as received without any additional purification. Mixed xylenes, vinyl acetate (VA), butyl acrylate (BA), butyl methacrylate (BMA), methyl methacrylate (MMA), styrene (St), and t-butyl hydroperoxide were obtained from Aldrich Chemical Company. Lupersol 575 (t-amyl peroxy (2-ethylhexanoate)) was supplied by Elf Atochem. Vazo 67 (2,2 -azobis(2-methylbutyronitrile)) was obtained from DuPont Chemical Company. Vinyl pivalate (NE05), vinyl 2-ethylhexanoate (V2EH), Tergitol NP-40 (non-ionic surfactant) and QP-300 (hydroxy ethyl cellulose) were obtained from Union Carbide Coq)oration. Aerosol OT-75 (surfactant) was obtained from Cytec. Sodium formaldehyde sulfoxylate was obtained from Henkel Corporation. Ethyl 3-ethoxy propionate (EEP), propylene glycol monomethyl ether (PM) and PM acetate (PM Ac) are Eastman Chemical Company products. 

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