Hydrosilylation of cinchonidine and 9-O-TMS-cinchonidine with triethoxysilane: application of 11-(triethoxysilyl)-10,11-dihydrocinchonidine as a chiral modifier in the enantioselective hydrogenation of 1-phenylpropane-1,2-dione

摘要

The detailed synthesis and characterization of (u0001)-11-(triethoxysilyl)-10,11-dihydrocinchonidine (4), a startingnmaterial for the immobilization of (u0001)-cinchonidine on silica based supports, is described. Compound 4 togethernwith its precursors 9-O-(trimethylsilyl)cinchonidine (2) and 9-O-(trimethylsilyl)-11-(triethoxysilyl)-10,11-dihydrocinchonidinen(3) were employed as chiral modifiers in the hydrogenation of a prochiral diketone, 1-phenylpropane-n1,2-dione, over a heterogeneous Pt/Al2O3 catalyst using cinchonidine (1) as a reference modifier. The unexpectednenhancement of ee induced by 4, demonstrating the positive effect of distal modifier substitution, is discussed innthe light of molecular modeling and NMR studies.