Stereoselective C9 Carbon−Carbon Couplings of Quinine: Synthesis and Conformational Analysis of New C2-Symmetric Dimers
摘要:
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 C-2-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 C-2-symmetric (9S)-quinine dinner connected solely by carbon-carbon bonds was obtained by the stereoselective coupling of bis(arylbromomagnesium) derivative with (9S)-chloroquinine.
Rabe, Justus Liebigs Annalen der Chemie, 1949, vol. 561, p. 154 Anm. 75
作者:Rabe
DOI:——
日期:——
Stereoselective C9 Arylation and Vinylation of <i>Cinchona</i> Alkaloids
作者:Przemysław J. Boratyński、Ilona Turowska-Tyrk、Jacek Skarżewski
DOI:10.1021/ol7026625
日期:2008.2.1
A simple and efficient method for the highly stereoselective C-9 arylation and vinylation of Cinchona alkaloids was developed. Both 9s- and 9R-chloroquinine with PhMgBr yielded 9S-phenylquinine (X-ray structure). The reactions with various aryl and vinyl Grignard reagents resulted in the series of 9S-aryl and vinyl alkaloid derivatives. The stereochemical outcome was rationalized by coordination of the magnesium atom to the quinuclidine nitrogen, thus directing the nucleophilic attack at the C-9 stereogenic center.