Date of Award
Doctor of Philosophy
The flash vacuum pyrolysis (FVP) of 1-trimethylsilyl-3-vinylallenes resulted in the formation of trimethylsilylacetylenes. A mechanism is proposed involving an initial 1,2-silyl migration to generate a vinyl carbene. The proposed mechanism is analogous to the energy pathway recently calculated for the rearrangement of allene to propyne;The FVP of vinylallenes required higher temperatures than did the analogous trimethylsilyl substituted vinylallenes and afforded acetylenes and cyclopentadienes. A mechanism was discussed to explain the products;Alkyl and aryl substituted trimethylsilylallenes were found to require higher temperatures to isomerize than 1-trimethylsilyl-3-vinylallenes. Products derived from initial 1,2-silyl and 1,2-hydrogen shifts were isolated;The only 1-trimethylsilylcyclopropene successfully synthesized and isolated was 3,3-dimethyl-1-trimethylsilylcyclopropene. The FVP of 3,3-dimethyl-1-trimethylsilylcyclopropene afforded the same products as were obtained from the FVP of the analogous allene;The FVP of 3-methyl-1,2-butadiene afforded isoprene and a mechanism involving a 1,2-hydrogen shift is proposed. Pasto's claim that isoprene is formed from the sealed tube thermolysis of 3-methyl-1,2-butadiene and diethylfumerate by a 1,3-H shift could not be commented on since the thermolysis of 1,1-dideuterio-3-methyl-1,2-butadiene and diethylfumerate did not afford any products derived from d[subscript]2-isoprene;The FVP of 2-trimethylsilylpropenal afforded ((trimethylsilyl)oxy)-1,2-propadiene, 1,3-butadiene, and siloxanes derived from dimethylsilanone. An initial 1,3-silyl migration generates ((trimethylsilyl)oxy)-1,2-propadiene which then fragments to 1,3-butadiene and siloxanes. The FVP of 3-trimethylsilylpropenal generated 2,2,3-trimethylsila-[alpha]-2,3-dihydrofuran and 2,5,5-trimethylsila-[alpha]-2,5-dihydrofuran.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Larry Richard Robinson
Robinson, Larry Richard, "A mechanistic study of the thermally-induced rearrangements of silylallenes in the gas phase " (1987). Retrospective Theses and Dissertations. 11723.