I. Synthesis of trimethylsilyl-substituted polymethylenes via the polyhomologation reaction. II. The borane-catalyzed oligomerization of ethyl diazoacetate: The role of carbon-boron enolates.

摘要

This dissertation includes two research projects on the synthesis and characterization of substituted polymethylenes. After an introduction to the polymerization of ethylene and the polyhomologation reaction in Chapter 1, Chapters 2, 3 and 4 describe the preparation of trimethylsilyl-substituted polymethylenes. Chapter 5 focuses on the mechanistic investigation of C-boron enolates in the reaction of borane and ethyl diazoacetate.;Chapter 1 gives a general introduction of various types of the simplest carbon backbone polymer, polyethylene, followed by a brief summary of several primary polymerization techniques of ethylene. The reminder of this chapter focuses on an overview of the polyhomologation reaction, a new carbon-carbon bond forming reaction for the synthesis of (substituted) polymethylenes one carbon at a time..;In Chapter 2, the synthesis of trimethylsilyl-substituted polymethylenes via polyhomologation is described. Oligomers were obtained from the trialkylborane-catalyzed copolymerization of trimethylsilyldiazomethane and dimethylsulfoxonium methylide. The resultant copolymer, poly(methylidene-co-trimethylsilylmethylidene), arises from incorporation of C1 building blocks, trimethylsilylmethylidene (CHSiMe3) and methylidene (CH2) groups.;Chapter 3 reports another new polymerization reaction for the synthesis of trimethylsilyl-modified polymethylenes. The polymerization of sulfonium ylides is capable of producing polymers with a CHSiMe3:CH 2 ratio higher than that obtained by vinyltrimethylsilane polymerization. In addition, the polymer is built up one carbon at a time from CH2 and CHSiMe3 fragments that are produced from a single monomer precursor, trimethylsilylmethyldimethylsulfonium iodide. .;Chapter 4 demonstrates that trimethylsilyldiazomethane can serve as monomer in the copper-mediated polymerization to afford poly(trimethylsilylmethylidene) oligomers. To our knowledge, this is the first example of the synthesis of a fully substituted polymethylene with trimethylsilyl group substituted on every carbon of the polymer backbone. The polymer was built up one carbon at a time from trimethylsilylmethylidene (CHSiMe3) fragments.;Chapter 5 describes the difference in chemical reactivity of borane (BH 3) and trialkylborane (BR3) towards ethyl diazoacetate (EDA). In the reaction of borane with EDA, insertion of the second equivalent of EDA with concurrent alkyl group migration eventually produces a stabilized doubly homologated C-boron enolate. This C-boron enolate and its homologated species are proposed as the resting states for the oligomerization of EDA. Evidence is also provided for the presence of doubly borylated enolates.