A Silicon‐Stereogenic Silanol ‐¹⁸O‐Isotope Labeling and Stereogenic Probe Reveals Hidden Stereospecific Water Exchange Reaction

Abstract

A silicon-stereogenic aminosilanol was isolated in excellent diastereomeric ratio and the absolute configuration was determined. The silanol is configurative and condensation stable in solution and shows stereoselective transformations with a clean stereospecific pathway in follow-up reactions, which leads to the isolation of a silicon-stereogenic zinc complex and siloxane compounds. Investigations with 18 O-labelled water and mass spectrometry analysis revealed an otherwise hidden exchange of oxygen atoms of silanol and water in solution that proceeds with retention of the configuration at the silicon center. This novel combination of a stereochemical probe and isotopic labeling in a siliconstereogenic compound opens new analytic possibilities to study stereochemical courses of reactions with the aid of chiral silanols mechanistically.

Multifunctional Chiral Silanol Ligands for Enantioselective Catalysis

“…[36,37] Furthermore, longer Si-O bonds can contribute to improved steric modulation and selectivity. Achiral silanols have been previously utilized as ancillary ligands for a variety of metal-catalyzed transformations [38] such as alkyne metathesis, [37,39,40] Pd-catalyzed cross-coupling [41][42][43][44] and orthometalation, [45][46][47][48][49] Strohmann has reported chiral zinc(II)silanoates, [50] including a stereogenic-silicon silanoate, [51] although no catalytic activity was documented. A notable example of a ferrocene-based chiral organosilanol ligand has been reported for an asymmetric phenyl-transfer reaction to substituted benzaldehydes with stoichiometric zinc reagents.…”