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.
achievement of the corresponding enantioselective transformations using the tetraorganosilicon reagents, providing the silicon-based approach to opticallyactiveketones and substituted piperidones that serve as synthetic intermediates of pharmaceuticals. A rhodium alkoxide species is suggested to be responsible for a transmetalation step on the basis of the observed kinetic resolution of a racemic chiral phenylsilane
Organomanganese (II) reagents XVI1: copper-catalyzed 1,4-addition of organomanganese chlorides to conjugated enones
作者:Gérard Cahiez、Mouad Alami
DOI:10.1016/s0040-4039(00)99434-6
日期:1989.1
Copper-catalyzed conjugate addition of organomanganese chlorides to conjugated enones in THF, at 0°C, leads to the 1,4 addition products in high yields. The scope of the reaction is very large and the results are generally better than those obtained from organomagnesium compounds in the presence of a copper salt as well as from organocopper or cuprate reagents. Furthermore organomanganese chlorides are indisputably
The reaction of organomanganese reagents such as RMnX, R2Mn, R3MnLi and R3MnMgX with cyclohexenone has been studied. Two major pathways have been observed : conjugate addition and β reductive dimerization. Similar results have been obtained with organomagnesium compounds in presence of a catalytic amount of manganous salts.