Alcohols, Halogeno-compounds, and Ethers

Hughes, A. Pelter, K. Smith, E. Negishi, and T. Yoshida, Tetrahedron Letters, 1976, 87. A. B. Levy and S. J. Schwartz, Tetrahedron Letters, 1976, 2201. 

and illustrates a new extension of the umpolung concept when taken alongside the classical Grignard reagent-formaldehyde approach to this conversion. 

The previously established pattern is maintained in this Report likewise cross-referencing to earlier Reports follows the style of Vols. 4 and 5, i.e. a citation (2,113) in the text refers to Vol. 2, page 113 in this series of Specialist Periodical Reports. 

Reagents i, HSiXa-HjPtCls ii, LiAlH4 iii, N(CH2CH20H)3-Co(CO)a iv, NlCHjCHjOHlj-KOH  

Regioselective ring opening of epoxides to the less-substituted alcohol, by hydride capture at the better potential carbenium ion centre, is achieved with a sodium cyanoborohydride-boron trifluoride combination anti ring opening is favoured. 

Wherever possible, reactions are listed according to the type of compound prepared. For example, ROH RC2 reactions are classified as halide preparations and not alcohol reactions. Exceptions are those reactions which are considered to be protection or deprotection procedures. Within each functional group class, preparations are discussed before reactions and it has been attempted to list the references in any one section in increasing order of reaction selectivity. Cross referencing to earlier reports follows the established style. 

RCH=CH2 -U Li [(RCH2CH2) AlH4- ] Reagents i, Cp2TiCl2-LiAlH4 ii, oxidation 

Lithium dialkylcuprates (R2CuLi) are known to react with epoxides to produce alcohols, but usually a large excess of cuprate is required and only one alkyl group is transferred. The use of cyanocuprates (1) in equimolar proportions circumvents these problems to give alcohols from monosubstituted epoxides as illustrated in equation (1) 1,2-disubstituted epoxides are opened at the more electrophilic carbon. 

A section on alcohol-forming reactions is included in a recent review of organo-bocates (such as cyano-, alkenyl-, and alkynyl-borates) in organic synthesis. 

An unusual reduction of tertiary amides to alcohols (equation (2)], i.e. with C—N fission, has been reported using lithium triethylborohydride, and seems to be general as long as the groups on nitrogen are small. 

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