I. New remote radical chain functionalization reactions. II. Structure and reactivity of polycyclic nitrogen heterocycle-chlorine radical complexes. III. Studies towards catalytic radical relay chlorination reactions.

摘要

I. Normal radical relay chlorination of 3{dollar}alpha{dollar}-cholestanol directed by an attached m-iodobenzoate ester group affords a 9{dollar}alpha{dollar}-chlorosteroid, but when the same reaction is conducted in the presence of an excess of carbon tetrabromide the product is a 9{dollar}alpha{dollar}-bromosteroid. Similarly, when the same chlorination reaction is carried out with thiocyanogen present, the product is a 9{dollar}alpha{dollar}-thiocyanosteroid. Several other examples of these reactions are given. They succeed because the same critical complexed chlorine-radical hydrogen abstraction takes place in each case. Preliminary work towards a similar tandem cyanation reaction is described. Syntheses of bifunctional templates which are intended to direct chlorine radical hydrogen abstraction and trap the resulting substrate radical are also described.; II. Polycyclic nitrogen heterocycle acids were esterified onto 3{dollar}alpha{dollar}-cholestanol to examine their ability to direct the chlorination reaction. Quinolines proved to be stable and efficient chlorination templates. An acridine also directed chlorination, but had to be stabilized by substitution at the acridine-9-position, to prevent template modification during the reaction. Studies of the selectivity of the chlorination of 2,3-dimethylbutane in the presence of additives indicated a 4-quinoline ester forms a more stable chlorine-radical complex than pyridine. This finding does not fit the previously found basicity/complex stability correlation observed with simple pyridine derivatives. Therefore, the structure of the 4-quinoline ester-chlorine radical complex may be different than that with pyridine. Attempts to obtain transient absorption or E.S.R. spectra of this complex were unsuccessful.; III. Catalysts for directed chlorination reactions were synthesized which featured templates with multiple binding sites for non-covalent interactions. The first catalysts bore ammonium groups for ion pairing with 3{dollar}beta{dollar},17{dollar}beta{dollar}-androstanedisulfate. However, significant reaction catalysis was not observed under a variety of conditions. The second catalysts were synthetic macrocyclic cavity dimers. Binding studies indicated the desired highly organized complex between steroid substrates and the dimeric host was not strongly favored.