Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Ethers, silyl enol reaction with organolithium

Benzyl methyl ether or allyl methyl ethers can be selectively metalated at the benzylic/allylic position by treatment with BuLi or sBuLi in THF at -40 °C to -80 C, and the resulting organolithium compounds react with primary and secondary alkyl halides, epoxides, aldehydes, or other electrophiles to yield the expected products [187, 252, 253]. With allyl ethers mixtures of a- and y-alkylated products can result [254], but transmetalation of the lithiated allyl ethers with indium yields y-metalated enol ethers, which are attacked by electrophiles at the a position (Scheme 5.29). Ethers with ft hydrogen usually undergo rapid elimination when treated with strong bases, and cannot be readily C-alkylated (last reaction, Scheme 5.29). Metalation of benzyl ethers at room temperature can also lead to metalation of the arene [255] (Section 5.3.11) or to Wittig rearrangement [256]. Epoxides have been lithiated and silylated by treatment with sBuLi at -90 °C in the presence of a diamine and a silyl chloride [257]. [Pg.166]

Enoxysilacyclobutanes. These compounds can be prepared by Wurtz coupling of 3-chloropropyltrichlorosiIane with Mg in ether. Introduction of one alkyl group is accomplished by reaction with an organolithium reagent, and the silyl chloride can then be used for the formation of silyl enol ethers. Such 0-silyl ketene acetals are extremely reactive in aldol condensations with aldehydes without catalysts. The reaction is syn-selective. An asymmetric version uses silyl ketene acetals bearing a chiral Si-alkoxy (e.g., 8-phenylmenthoxy) group instead of an alkyl substituent. [Pg.98]


See other pages where Ethers, silyl enol reaction with organolithium is mentioned: [Pg.546]    [Pg.26]    [Pg.1639]    [Pg.286]    [Pg.19]    [Pg.284]    [Pg.185]    [Pg.1301]    [Pg.413]    [Pg.302]    [Pg.647]    [Pg.270]    [Pg.668]    [Pg.98]   


SEARCH



Enolates silylation

Enolates, silyl reactions

Enols reactions with

Organolithium reaction

Reaction with enol silyl ethers

Reaction with ethers

Reaction with organolithium

Reactions, with enol ethers

Reactions, with enolates

Silyl enol ethers

Silyl enol ethers reaction

Silyl enolate

Silyl enolates

Silyl ethers reaction with

Silyl ethers reactions

Silyl reactions with

Silylation reactions

Silyls reactions with

© 2024 chempedia.info