Ring substitution 376 Vinylic alcohol

The second method involves end-quenching of living polymers with appropriate nucleophiles. Although this approach appears to be more attractive than the first one, in situ end funaionali-zation of the living ends is limited to nucleophiles that do not react with the Lewis add coinitiator. Because the ionization equilibrium is shifted to the covalent spedes, the concentration of the ionic active species is very low. Quantitative functionalization can only be accomplished when ionization takes place continuously in the presence of nudeophile. Quenching the vinyl ether polymerization with the malonate anion,certain silyl enol ethers " and silyl ketene acetals have been successfully used to synthesize end-functionalized poly(vinyl ethers). Alkyl amines, " ring-substituted anilines, " " alcohols, " and water " have also been used to quench the vinyl... 

Vinyltrimethylstannanes react with xenon difluoride in dichloromethane at room temperature in the presence of equimolar (or a 50 Vo excess) of silver trifluoromethanesulfonate and a catalytical (0.1 equiv) quantity of 2,6-di-/e/7-butyl-4-methylpyridine to form the corresponding vinyl fluorides in high to moderate yields.54 57 The substitution reaction is tolerant to various functional groups, such as ketones, esters, carbamates, ketals, ethers, phenol rings and tertiary alcohols. As byproducts corresponding alkenes have been detected due to pro-tiodestannylation. 

Slightly more exotic carbon-centered nucleophiles can also participate in the ring-optening of epoxides. For example, the vinyl metallate 81, prepared by the treatment of the alkenyl acetal 86 with Schlosser s reagent, attacks mono-substituted epoxides 82 at the C-2 position to give the labile homoallyl alcohols 83 in fair to very good yields <96TET1433>. 

Several epoxides hearing multiply-bonded substituents have Wu subjected to alcohol addition. Treatment of several vinyl-substituted ethylene oxides with sodium metboxide, for example, has been reported to yield alcohols corresponding to attack on the epoxide carbon iLtnnt furthest from the uiwaturated function. 6-l8S8- . > In the presence of a trace of mineral acid, however, methanol adds to the opposite terminal of the epoxide ring (Eq. 666),... 

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