A FACILE SYNTHESIS OF BICYCLO[M.N.1]ALKAN-1-OLS - EVIDENCE FOR ORGANOSAMARIUM INTERMEDIATES IN THE SAMARIUM(II) IODIDE PROMOTED INTRAMOLECULAR BARBIER-TYPE REACTION

Samarium(II) iodide (SmI2) has been successfully employed as a reductive coupling agent for the intramolecular Barbier-type synthesis of bicyclo[m.n.1]alkan-1-ols. Thus, a variety of 3-(omega-iodoalkyl)cycloalkanones, upon treatment with SmI2 and a catalytic quantity of iron complex in tetrahydrofuran (THF), provide the title compounds in excellent yields. The reaction is quite general for the construction of diverse bicyclic ring systems, including the highly strained bicyclo[2.1.1]hexan-1-ol. In addition to exploring the synthetic utility of this reaction, studies have been performed which provide insight on the mechanistic details of the SmI2-promoted intramolecular Barbier-type synthesis. Compelling evidence for the intermediacy of organosamarium species has thus been gathered.