Highly Selective Methyl Transfer from Methylsilanes to Phenylthallium(III) Crown Ether Complexes

Reactions of (18-crown-6) phenylthallium(III) diperchlorate monohydrate (1a) with Me₃SiR (R = PhCH₂, Et, Ph, CH═CH₂, SiMe₃, OSiMe₃) proceeded at 60 °C to provide (18-crown-6)phenylmethylthallium(III) Perchlorate (3) in good to excellent yields. Cleavage of the Me-Si bond in tetramethylsilane using 1a also occurred at 25 °C, albeit for a long reaction time. The silicon-containing products of the reaction of 1a with benzyltrimethylsilane were siloxanes. Intramolecular trapping of the silyl fragment by a hydroxy group using (1,7-DTC)phenylthallium(IIT) bis(trifluoromethanesulfonate) (1b) was employed with trans-2-((trimethylsilyl)methyl)-1-cyclohexanol, affording a bicyclic silyl ether in 92% yield.