Studies On The Cascade Cyclization Of "Estera-ENS" Coupling For The Synthsis Of Bridge Cyclic Alcohols Mediated By Allyic Samarium Bromide

Samarium diiodide as a single-electron transfer agent has been widely explored in organic synthesis, while reports concerning the use of allylSmBr as a single-electron transfer agent are very few despite its divalent samarium. In this dissertation, the studies on the application of allylSmBr as a single-electron transfer agent have been carried out so as to synthesize a series of bridged cyclic alcohols. The dissertation consists of two parts:The first part of the study is based on the previous results of our group. By introducing an additional C=C bond in the homoallylic esters, the "ester-ene" coupling was accompanied by radical addition and then Barbier reaction to convert into bridged cyclic compounds. The good yields and high diasteroselectivity are impressive. During the optimizaion process, the use of CuCl2·2H2O as the additive was found to afford satisfactory yields. The role of this additive was discussed. And a reasonable mechanism was proposed.In the second part, the "ester-ene" coupling was further applied in the synthesis o f variously substituted bicyclo[3.1.0]hexan-l-ols, oxabicyclo[3.1.0]hexan-l-ols and azabic yclo[3.1.0]hexan-l-ols. Again, high diastereoselectivity was observed. Optically pure aza bicyclo[3.1.0]hexan-l-ols and oxabicyclo[3.1.0]hexan-l-ols were readily prepared form n atural a-amino acids and a-hydroxy acids respectively in moderate yields.