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Metallo Groups

Although a limited range of Grignard reagents is available, the most widely used group is undoubtedly the lithio group introduced by direct lithiation (see Section 3.3.1.6.2). The ready formation of the lithio derivatives of pyrroles, furans and thiophenes and their benzo-fused derivatives has had a most important impact on the chemistry of these heterocyclic systems. Reaction of the [Pg.357]

Reactivity of Five-membered Rings with One Heteroatom [Pg.358]

The dianions of methylated thiophenecarboxylic acids (e.g. 391) are also readily generated by reaction with LDA they undergo preparatively useful reactions with a range of carbon electrophiles [Pg.358]

Regioselective side-chain lithiation could also be carried out on 2-methylthiophene-3-carboxylic acid. By contrast, the isomeric 3-methylthiophene-2-carboxylic acid gives a 35 65 mixture of side-chain and nuclear (at position 5) lithiation (80JOC4528). Dilithiation of 2-methylthiophene-3-carboxylic acid with 2 equivalents LDA in THF at - 30°C gave only the dilithium derivative (392) (80%), which could be reacted with electrophiles at the methylene carbon (89BCJ2725). [Pg.358]

Treatment of tri-(2-thienyl)methane with BunLi in the presence of TMEDA in THF at — 78°C gives exclusively the tri-(2-thienyl)methyllithium (393) (96%) without any nuclear lithiation (92CL703). This lithiation is faster than that of triphenylmethane. Treatment of (393) with primary alkyl halides leads to alkylation at the carbanion center, forming (394). However, secondary alkyl halides give mixture of (394) and (395). [Pg.358]


The TV-protected pyrrole (212) can be palladated, but not lithiated, in the 3-position to give the stable complex (213) this is readily converted into the 3-methoxycarbonylpyrrole (214) (82JOM(234)l23). The use of palladium derivatives thus further increases the range of transformations made possible through the intermediacy of metallo groups. [Pg.83]

Allylic zinc bromides add to vinylic Grignard and lithium reagents to give the cm-dimetallo compounds 65. The two metallo groups can be separately reacted with various nucleophiles. ... [Pg.1027]

JOM(234)l23). The use of palladium derivatives thus further increases the range of transformations made possible through the intermediacy of metallo groups. [Pg.365]


See other pages where Metallo Groups is mentioned: [Pg.39]    [Pg.79]    [Pg.878]    [Pg.357]    [Pg.39]    [Pg.79]    [Pg.742]    [Pg.832]    [Pg.39]    [Pg.79]    [Pg.742]    [Pg.832]    [Pg.742]    [Pg.819]    [Pg.249]    [Pg.249]    [Pg.275]    [Pg.294]    [Pg.297]    [Pg.492]    [Pg.589]   


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