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Improved and efficient synthesis of chiral N,P-ligands via cyclic sulfamidates for asymmetric addition of butyllithium to benzaldehyde.

Organic letters (2007-08-19)
Petra Rönnholm, Mikael Södergren, Göran Hilmersson
ABSTRACT

A robust and scaleable route to chiral 1-isopropylamino-2-(diphenylphosphino)ethanes is described via the ring-opening of chiral, cyclic sulfamidates with potassium diphenylphosphide (KPPh(2)). The novel protocol offers a robust access to gram quantities of chiral amino phosphinoethanes in high yields. The Li-amides of the chiral aminophosphines were evaluated as chiral ligands in the asymmetric addition of n-butyllithium (BuLi) to benzaldehyde, yielding 1-phenylpentanol up to 98% ee.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
n-Butyllithium solution, 2.7 M in heptane
Sigma-Aldrich
n-Butyllithium solution, 2.5 M in hexanes
Sigma-Aldrich
n-Butyllithium solution, 11.0 M in hexanes
Sigma-Aldrich
n-Butyllithium solution, 2.0 M in cyclohexane
Sigma-Aldrich
n-Butyllithium solution, 1.6 M in hexanes
Sigma-Aldrich
n-Butyllithium solution, 1.4 M in toluene