Bicyclic bases. Synthesis, configuration, and NMR analysis of N-tosyl-2-thia-5-azabicyclo[2.2.1]heptane-2-oxides

The novel bicyclic system, N-tosyl-2-thia-5-azabicyclo[2.2.1]heptane (IV), was synthesized from tritosylhydroxy-L-prolinol and thioacetate anion. Sodium metaperiodate oxidation of (IV) yielded exclusively the exo sulfoxide (VI) from which the isomeric endo product (VIII) was obtained by treatment with ethyloxonium fluoroborate. Thermally induced equilibration studies demonstrated that the exo-oxide is thermodynamically more stable than the endo-oude. The sulfone (V) was prepared by oxidation with H₂O₂. The identity of all proton resonances in the 100-MHz NMR spectra of (IV-VI, VIII) were deduced from spin-decoupling experiments.