Birch reduction, cyclohexane

Birch reduction (Section 11 11) Reduction of an aromatic nng to a 1 4 cyclohexadiene on treatment with a group I metal (Li Na K) and an alcohol in liquid ammonia Boat conformation (Section 3 7) An unstable conformation of cyclohexane depicted as... 

R. Taylor. We tried the Birch reduction and obtained amino peaks in the ir because amination occurs under the reaction conditions. We tried to get over this problem by hydrogenating over platinum at low pressure, initially in hexane and then in benzene. Benzene must be redistilled first because it contains di-octyl phthalate. Having adopted this precaution, a purple solution was obtained which became bright yellow after 2-3 days. Of course benzene is reduced as well to cyclohexane. Another problem arises because the (hydrogenated) product, although initially soluble in... 

Fundamental to the development of dienyl iron tricarbonyl chemistry has been the availability of substituted cyclohexadiene precursors arising from the Birch reduction. In this process, a wide range of aromatic compounds are readily reduced to their corresponding unconjugated cyclohexa-1,4-dienes without further reduction to a cyclohexane. The reaction is typically performed by adding sodium to a liquid ammonia solution of the substrate in the presence of an added alcohol. 

Proline derivatives have also been used in enantioselective tandem Birch reduc-tion/alkylation sequence [33]. In 1984, Schultz reported the enantioselective alkylation reaction of an amide enolate derived in the course of a Birch reduction [34]. This reaction serves as a versatile tool for the enantioselective construction of highly substituted cyclohexanes bearing a chiral quaternary carbon center. A variety... 

Preparative electrochemical reduction of aryltrimethylsilanes in methyl-amine in the presence of LiCl gives the Birch-type products, 1,4-cyclohexan-dienes (Scheme 34) [6], A mechanism involving the electrochemical formation of lithium metal which chemically reduces the substrate has been suggested. The hydrogen atom is introduced on the carbon adjacent to the silicon preferentially. This regioselectivity is consistent with the spin density of the anion radical determined by ESR spectroscopy (Sect. 2.2.1). 

The reaction of the same initial compound (257) with 1,2-cyclohexane-dione leads to the triketone (260), the cyclization of which forms compound (263). The exhaustive reduction of the latter by Birch s method has given the 18,19-bisnor-D-homosteroid (264) which possess a feeble andro-... 

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