Sulfuration of the norbornene double bond: formation and reactions of norbornane trithianes and pentathianes; Molecular rearrangements of fused norbornene ring systems and their heterocyclic counterparts

Abstract

Part A. The reaction of sulfur with a variety of norbornene and sesquinorbornene double bonds has been investigated and a number of norbornane trithianes and pentathianes have been isolated and characterized. Helpful correlations between proton NMR chemical shifts and the number of sulfur atoms in the rings have been found to exist in these systems. An equilibrium has been found to exist between pentathianes, trithianes and sulfur. How understanding this equilibrium might throw light on the mechanism of the sulfuration reaction has been discussed. Oxidation of the norbornane trithianes with different oxidizing agents gave a variety of 1-sulfoxides and 2-sulfoxides. A novel isomerization of an endo-sulfoxide to an exo-sulfoxide has been observed. Some of the trithianes have been found to act as donors of the S(,3) unit. This transfer reaction has been investigated in detail and all the data indicate the transfer to be a concerted process. Part B. The rearrangement of 10-oxabenzo-syn-sesquinorbornene by light and by acids has been studied. The rearranged product has been found to be 2,3-norborneno-1-naphthol whose methyl ether is formed by the acid rearrangement in methanol. The mechanism of the rearrangement is discussed. The stable carbocation generated from 10-oxabenzo-syn-sesquinorbornene has been analyzed by ('13)C NMR. In an effort to synthesize the rearranged product from a different route, the acid catalyzed reaction of cyclopentadiene with 1-naphthol has been investigated. The products have been found to be the 2- and 4- cyclopentenyl-1-naphthols. A norbornanopyrrole has been synthesized by the reaction between 2,3-diacetyl norbornane and aniline. A side product in this reaction is a novel 1,3-aminal. The aldol condensation of diacetyl derivatives of both the tricyclic 2.2.1 and tricyclic 2.2.2 system has been studied. It has been found that in the 2.2.1 system the aldol products have primarily the exo configuration while in the 2.2.2 system the endo configuration is predominant. A (4+2) cycloaddition mechanism has been proposed for the formation of the 1,3-aminal.