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Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
Published on: October 18, 2019
Chiral Chalcogenyl-Substituted Naphthyl- and Acenaphthyl-Silanes and Their Cations
Sandra Künzler1, Saskia Rathjen1, Katherina Rüger1
1Institut für Chemie, Carl von Ossietzky Universität Oldenburg, Carl von Ossietzky-Str. 9-11, 26129, Oldenburg, Germany, European Union.
Abstract:
Cyclic silylated chalconium borates 13[B(C6 F5 )4 ] and 14[B(C6 F5 )4 ] with peri-acenaphthyl and peri-naphthyl skeletons were synthesized from unsymmetrically substituted silanes 3, 4, 6, 7, 9 and 10 using the standard Corey protocol (Chalcogen Ch=O, S, Se, Te). The configuration at the chalcogen atom is trigonal pyramidal for Ch=S, Se, Te, leading to the formation of cis- and trans-isomers in the case of phenylmethylsilyl cations. With the bulkier tert-butyl group at silicon, the configuration at the chalcogen atoms is predetermined to give almost exclusively the trans-configurated cyclic silylchalconium ions. The barriers for the inversion of the configuration at the sulfur atoms of sulfonium ions 13 c and 14 a are substantial (72-74 kJ mol-1 ) as shown by variable temperature NMR spectroscopy. The neighboring group effect of the thiophenyl substituent is sufficiently strong to preserve chiral information at the silicon atom at low temperatures.
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