Synthesis and Characterization of Base‐catalyzed Phenyl Modified PDMS/PHMS Copolymers

A series of phenyl modified polydimethylsiloxane (PDMS) / polyhydrogenmethylsiloxane (PHMS) random copolymers containing both internal Si‐H and terminal SiH₂ and T (MeSiO_3/2) units was synthesized in one step through n‐BuLi‐catalyzed ring‐opening polymerization of cyclic comonomers and characterized by GPC, IR and ¹H and ²⁹Si NMR. Sequential microstructures of these copolymers were determined by ²⁹Si‐NMR spectroscopy. Epoxy‐modified polysiloxanes were prepared and used as comparable standards for the assignment of the NMR spectra. A hydride‐transfer mechanism has been proposed to account for the formation of terminal Si‐H and T group. Detailed sequential analyses and chemical shifts of ²⁹Si‐NMR for various siloxane units are reported for the first time.     

Synthesis of 1-Tosyl-4,6-dihydrothieno[3,4-d]pyrazole 5,5-Dioxides as Precursors to Pyrazole Analogue of o-Quinodimethane

A facile synthesis of 3-substituted 1-tosyl-4,6-dihydrothieno[3,4-d]pyrazole 5,5-dioxides from readily prepared 3-(phenylthio)-4-acyl-3-sulfolenes and their use as precursors to o-dimethylene pyrazole in [4 + 2] cycloaddition are described.