Free-radical clocks in the aliphatic S[subscript RN]1 process and reactions of nucleophiles with 1,1-dinitro-2,2-diphenylethylene

摘要

Part I of this dissertation involves the continuing investigation of the aliphatic S(,RN)1 process. 1-Chloro-1-cyclopropyl-1-nitroethane and 2-chloro-2-nitro-6-heptene were synthesized as qualitative timing devices to investigate the rate of radical-anion trapping in one of the propagation steps of the aliphatic S(,RN)1 process. Unfortunately, the competing unimolecular radical reactions of the appropriate free-radical clocks were never observed and limited relevant information was obtained by product analysis. A further extension of the aliphatic S(,RN)1 process included in Part I is the first reported example of a carbon leaving group which will be added to the already impressive array of poor nucleofuges involved in S(,RN)1 reactions;In Part II, the reactions of a series of nucleophiles with 1,1-dinitro-2,2-diphenylethylene is reported. Although a variety of substitution products have been observed, there is no evidence for a free-radical chain reaction as judged by the lack of photostimulation and the absence of retardation by radical scavengers and powerful one-electron acceptors. Anions such as enolates, dialkyl phosphite ions and cyanide ion add to 1,1-dinitro-2,2-diphenylethylene to form the dinitromethide ion which can be isolated as Michael adducts. With nucleophiles such as RS-, PhSe-, PhO-, the intermediate dinitromethide ion undergoes rearrangement via an oxiranyl of episulfonium zwitterion to form a substitution product. Other nucleophiles lead to the formation of the dinitromethide ion, which can rearrange or hydrolyze to form benzophenone.