Synthesis and Optical Resolution of Configurationally Stable Zwitterionic Pentacoordinate Silicon Derivatives

Stereogenic silicon centres in functionalised tetracoordinated organosilanes generally exhibit very high configurational stability under neutral conditions. This stability drops completely when higher coordination states of the silicon centre are reached due to rapid substituent exchange. Herein we describe the synthesis of chiral and neutral pentacoordinate silicon derivatives with high configurational stability. The zwitterionic nature of these air‐ and water‐tolerant species allows for the first time their direct and efficient optical resolution using chiral HPLC techniques. By means of this method, pentacoordinate silicon compounds exhibiting high Si‐inversion have been obtained as single enantiomers. A rationalisation of the enantiomerisation pathways has been also carried out using DFT calculations. The synthesis of air‐ and water‐tolerant zwitterions featuring a chiral pentacoordinate silicon moiety is described. Their stability toward moisture and aerobic conditions allowed their optical resolution by means of chiral HPLC, which constitutes a premiere in the chemistry of organosilicon compounds. Studies on the kinetics of racemisation of enantiomerically pure substrates attest for their high configurational stabilities in solution.