| New synthetic uses of halonium ions-producing agents were developed towards an array of organic compounds such as aromatics, alkenes, ketones, {dollar}alpha,beta{dollar}-unsaturated ketones, {dollar}alpha,beta{dollar}-unsaturated esters and haloalkynols. The reactivities of three broad classes of halonium-producing agents were examined; most were effective in the presence of Lewis acids. The first class includes compounds containing nitrogen-halogen bonds, such as 5,5-dimethyl-1,3-dichlorohydantoin (DCH) and N-iodosuccinimide (NIS). With para-toluenesulfonic acid (p-TsOH) as catalyst, DCH was found to chlorinate several polyalkylbenzenes and to {dollar}alpha{dollar}-chlorinate ketones. In combination with p-TsOH, NIS was used to effect transformations of alkenes to trans-iodohydrins which were converted readily to epoxides with base. This method serves as a preliminary work to find optimum conditions for synthetic routes to chiral epoxides. The second class covers combinations of hypervalent iodine compounds, such as (hydroxy(tosyloxy)iodo) benzene (HTIB), with ionic salts such as halides and azide. With iodide, bromide, and chloride ions, this reagent was found to halogenate several aromatic compounds. Replacement of halide ions with azide effected a mild azidation of mesitylene. Simple iodine makes up the last class which in the presence of stoichiometric amounts of HTIB was found to be an effective reagent to induce phenyl shifts in haloalkynols. The NIS/catalytic p-TsOH duo was also useful for inducing phenyl shifts. Iodine's ability to {dollar}alpha{dollar}-iodinate {dollar}alphabeta{dollar}-unsaturated ketones and esters was examined and the function of amines in these processes was defined. Bicyclo (2.2.1) -ketones such as norcamphor and camphor also underwent mild one-carbon ring expansions to bicyclo (3.2.1) -{dollar}beta,beta{dollar}-dihaloenones. The reaction of iodine/HTIB with the iodoalkynol derivative of the commercially available 1,2-isopropylidene-{dollar}alpha{dollar}- scD-xylofuranose led to two compounds tentatively identified as a furo (2.3,c) pyran and a ketohexose. With an iodoalkynol derivative of diacetone- scD-glucose, ring expansion was effected as well. |
