Der Enolether (II) läßt sich, wie an einigen Beispielen gezeigt ist, durch Einsatz von Adamantanderivaten und ‐analogen zu den entsprechenden Produkten alkylieren.
A previously described method consisting in reacting LDA with u-bromoketones has been ertended t o u-bromoesters. DeshaZogemtion ( a f t e r hydrolysis) and f o n a t i o n of ketene alkyZtrimethyZsiZyZ acetaZ8 ( a f t e r SiMejCZ addition) occur and show the genemZity of the method.
Attemps to prepare 2-bromo-2,4-dimethyl,3-trimethylsiloxy 3-pentene reacting lithium diisopropylamide (LDA) with 2-bromo-2,4-dimethyl-3 pentanone have revealed two new reactions. After a few minutes quantitative yields are obtained of either the dehalogenated ketone (after hydrolysis) or the trimethylsilyl enol ether (after addition of trimethylsilyl chloride). These reactions are general and have been extended to other a-monobromoketones and a,a'-dibromoketones. In the latter case, the reaction is more complex and leads generally to dehaloqenation or reduction products.L'a-tertioalkylation des cetones via leurs ethers d'enol trimgthylsilyliques est maintenant une reaction bien connue (1,2). Etudide initialement avec des &tones aliphatiques, elle a 6te dtendue aux mod6les alicycliques puis 3 d'autres fonctions, les esters par exemple (1,2).La nature du groupe alkylant a elle-m8me varig d'un groupe alkyle tertiaire de la serie aliphatique (1,2) a la serie cyclanique (1) ou bicyclique por-
The α‐bromoketones (I) react with LDA and chlorotrimethylsilane to give the enol ethers (II) after aqueous work‐up, and with LDA and H2O to give the debrominated ketones (III), The initial product is in both cases the corresponding α‐arninoketone, which eliminates N‐isopropylideneisopropylamine to afford an anion which, on treatment with the reagents, gives the final products.
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