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Application of rapidly generated bidentate ligand libraries to zinc catalyzed reductions

2012; Elsevier BV; Volume: 716; Linguagem: Inglês

10.1016/j.jorganchem.2012.06.013

1872-8561

Tariq Zaman, Robin Frauenlob, R.D. McCarthy, Carolyn M. Walsh, E. Bergin,

Organoboron and organosilicon chemistry

A methodology for the combinatorial synthesis of bidentate ligands – allowing direct screening of reaction products without the need for isolation or purification – has been employed in a zinc catalyzed hydrosilylation. This reaction allowed the robustness of the methodology to be examined, by employing it in a challenging case where the metal complex is not pre-formed prior to catalysis. Four different ligand families have been examined: imines, aminals, bis-imines and oxazolines and related compounds, with a small library of each type produced and directly screened in the reaction. Three ligands providing enantioselectivities of 50% or more in this very challenging reaction were identified, and ees and conversions were equivalent whether the ligand was obtained as a crude mixture from a library synthesis or as an isolated, purified compound.