When more than one diastereomer is formed in an organic process than any other, this is known as diastereoselectivity. Cis/trans descriptors lose their validity when the only bond connecting the two centres is free to spin. Depending on the particular metal, the following changes in the diastereoselectivity of the enantioselective addition of various allylic organometallic reagents to carbonyl compounds, catalysed by either chiral Lewis acids or bases, or chelating ligands:
Independent of the initial allylic geometry,
(a) Si, Sn, and B allylic reagents mostly produce syn diastereoselectivity;
(b) Regardless of the initial allylic geometry, allylic reagents including Cr, Zn, and In produce mostly anti diastereoselectivity;
(c) The E/Z ratio of the beginning allylic geometry is reflected in the syn/anti diastereoselectivity of allylic trichlorosilanes (SiCl3).
Enrico Paris
CREA-IT, Italy
Dai Yeun Jeong
Asia Climate Change Education Center and Jeju National University, Korea, Republic of
Title : Techniques for carbon dioxide sequestration and the way forward
Collin G Joseph, University Malaysia Sabah, Malaysia
Title : Application of vanadium and tantalum single-site zeolite catalysts in heterogeneous catalysis
Stanislaw Dzwigaj, Sorbonne University, France