Date of Award
Doctor of Philosophy
In Chapter I of this dissertation, the Skattebol-type rearrangement (in THF solution at -78(DEGREES)) of anti-7-bromo-syn-7-lithiobicyclo4.1.0hept-2-ene (34-anti) and its C('7)-epimer (34-syn) is investigated. The following discoveries demonstrate that, in solution, this rearrangement proceeds through a carbenoid: (a) carbenoid 34-anti undergoes 1,3-rearrangement and generates the carbenoid coupling products 42-syn and 42-anti 17 times faster than does 34-syn, (b) the coupling products 42-syn and 42-anti are formed in a much different ratio from 34-anti (7.5 to 1) than from 34-syn (1.5 to 1), (c) no carbene trapping products were formed in the presence of a large excess of isobutylene, cyclohexene, or triethylsilane, and (d) the saturated analogs of 34-anti and 34-syn (i.e., 89-anti and 89-syn, respectively) do not generate the corresponding free cyclopropylidene under the same reaction conditions (or under a variety of other reaction conditions which are investigated in Chapter II);In Chapter III, the pyrolysis reactions of anti-7-bromo-syn-7-trimethylstannylbicyclo4.1.0hept-2-ene (35-anti) and its C('7)-epimer (35-syn) are studied, in hopes of observing the Skattebol rearrangement of the corresponding cyclopropylidene. The results of the gas-phase pyrolysis studies are not easily understood. In the solution phase, however, the pyrolysis reactions of 35-anti and 35-syn have both been discovered to involve initial C-Br bond heterolysis, with no carbene involvement. The reaction of 35-anti involves an ionic 1,3-rearrangement (through double bond participation), and that of 35-syn involves an ionic opening of the cyclopropyl ring (favored by the stereochemistry of the bromine group);Chapter IV describes the solution-phase pyrolysis reactions of the saturated analogs of 35-anti and 35-syn (205-anti and 205-syn, respectively). Both reactions again involve initial C-Br bond heterolysis. The major reaction pathway of 205-anti is C-Br bond heterolysis, leading to a cyclopropyl ion pair, which, in the absence of cation traps, loses trimethyltin bromide, to generate the corresponding cyclopropylidene. The major reaction pathway of 205-syn is ionic opening of the cyclopropyl ring (again favored by the stereochemistry of the bromine group).
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Robert D. Herold
Herold, Robert D., "The carbene/carbenoid chemistry of lithium and tin cyclopropylidenoids " (1984). Retrospective Theses and Dissertations. 8997.