Synthesis of a silanol-substituted proline analog as organocatalyst

Abstract

A proline-derived silanol, was designed as a novel potential organocatalyst, and synthesized starting from the tetrazole 3. The central idea was the combination of an acidic (tetrazole) and a basic functionality (pyrrolidine) with a silanol moiety in the same molecule. The synthesis of 7 was performed in four reaction steps starting with the tetrazole 3. In the solid state (X-ray crystal structure analysis) the crucial functional groups show a favorable orientation. A chiral HPLC method and a chiral capillary electrophoresis method have been established for the investigation of the kinetic resolution of the racemic alcohols 9 and 11. Acetylation reactions of alcohols were not accelerated by the organocatalyst 7, and the produced ee values were rather low.