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Stereoselective C9 carbon-carbon couplings of quinine: synthesis and conformational analysis of new C2-symmetric dimers.

The Journal of organic chemistry (2008-08-09)
Przemysław J Boratyński, Ilona Turowska-Tyrk, Jacek Skarzewski
ABSTRACT

An unexpected stereoselective direct dimerization occurred when 9-quinine halide was treated with butyllithium. The reaction of either (9S)- or (9R)-chloroquinine gave the same C2-symmetric dimer with 9R configuration (X-ray structure). A tentative mechanism involving radical recombination is discussed. This highly congested dimer forms two atropisomers, and their reversible interconversion was studied by NMR. Another C2-symmetric (9S)-quinine dimer connected solely by carbon-carbon bonds was obtained by the stereoselective coupling of bis(arylbromomagnesium) derivative with (9S)-chloroquinine.

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