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
摘要:
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.
CC bonds of γ-iodo carbonyl substrates has been realized by the effective use of a combined Lewis acid/base system consisting of aluminum tris(2,6-diphenylphenoxide) . This new amphiphilic bond cleavage reaction can be applied to a wide variety of γ-iodo carbonyl substrates and therefore serves as a highly efficient and general route to both cyclic and acyclic unsaturated carbonyl compounds.
Three reagents are introduced for radicalallylations: 3-phenylthio-2-bromopropene, 2,3-bis(trimethyl-stannyl)propene, and 3-tris(trimethylsilyl)silylthiopropene.