Fourteen-member silacycle built by cascade reactions induced by a platinum catalyst

Abstract

Aiming at the synthesis of platinum complexes, a ligand containing a dimethylsilane moiety was designed by a two-step reaction, respectively Williamson ether synthesis and carbonyl-amine condensation, starting from bis(chloromethyl)dimethylsilane, 3,5-dichlorosalycylaldehyde and 2-aminophenol. By reacting the new bis-imine with Pt(acac)2, an uncommon cyclic structure without metal has been obtained. Thereby, a deep insight into the reaction mechanism and reaction conditions was required, the 2D NMR and MALDI-MS studies revealing the rearrangement processes and cascade reactions that occur in three main steps, respectively imine cleavage, aldol condensation, and a new imine bond formation. The structures of the intermediate and final compounds were elucidated by elemental, spectral (FTIR, NMR, MS), and single-crystal X-ray diffraction analyses. Computer-assisted calculations (DFT method) were also performed to estimate the thermodynamic parameters of the reaction mechanism considered. The current study brings to attention one of the biggest silacycle ever reported and many other interesting particularities.