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Alkali Metal Alcoholates for Organic Synthesis
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Alcoholates are moderately strong base reagents that are used in many drug and
chemical synthesis applications, such as alkylation, arylation, acylation, solvolysis
of esters, condensation, elimination, isomerization, rearrangements, transfer
hydrogenation, Wittig reactions, and redox reactions. The reactivity can be !ne
tuned to the desired reaction by correct choice of alcoholate and counterion. The
wide range of properties and solubilities available from BASF Corporation allows for
process optimization and high yields. |
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The base strength can be varied with choice of solvent and the structure of the
alcohol. In dimethyl sulfoxide (DMSO), the ion aggregrates are solvated thus
increasing the basicity. As alkyl groups are added to the alcohol, the alcoholate
becomes a stronger base compared to primary alcoholates and hydroxide.
Furthermore, the higher base strength and steric bulk of the tertiary alcoholates
in"uence the speed, selectivity, and speci!city.
Primary alcoholates are in general only soluble in the alcohol from which they are
derived. Secondary and tertiary alcoholates are soluble in ethers, and when the
tertiary alcohol is branched high solubility in hydrocarbons is achieved. Due to
their higher solubility, tertiary alcoholates can be used in combination with an alkyl
lithium to generate a “Superbase”. Superbases are used in polymerization and
functionalization of polymers.
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Sodium tert-Butylate (STB)
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Sodium tert-butylate is more soluble than KTB in hydrocarbon solvents but is
minimally soluble in tertiary butanol. STB replaced sodium hydride in the synthesis
of a key intermediate for the antiviral drug, adefovir dipivoxil. The switch provided a
robust process with consistent yields and purities. |
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Palladium catalyzed intramolecular carboamination reactions gave excellent
diastereoselectivity and yields of indanylpyrrolidines. |
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