Primary alcohol deoxygenation

Ar= 2,4,6-trichlorophenyl, ) Best method for deoxygenation 4-fluorophenyl J of primary alcohols... 

Radical deoxygenation. Tosylates of primary alcohols undergo deoxygenation in 75-100% yield by treatment with Nal and Bu,SnH in DME at 80°. This radical reduction can be applied to tosylates of secondary alcohols, but the rate of reaction is slower and yields are only moderate.1... 

This procedure gives good yields from secondary alcohols and, by appropriate adjustment of conditions, can also be adapted to primary alcohols.132 Scheme 5.7 illustrates some of the conditions which have been developed for the reductive deoxygenation of alcohols. 

Primary alcohols can also be deoxygenated by radical chemistry [11a,lib]. However, it requires a higher temperature to break the carbon-oxygen bond in radical 13. Secondary alcohols can be conveniently deoxygenated in benzene under reflux (80°C), but primary alcohols require toluene or xylene under reflux. 

Primary alcohols (a) D. H. R. Barton, W. B. Motherwell, and A. Stange, Radical-induced deoxygenation of primary alcohols, Synthesis, p. 743 (1981) (b) D. H. R. Barton, P. Blundell, J. Dorchak, D. O. Jang, and J. C. Jaszberenyi, The invention of radical reactions. Part XXI. Simple methods for the radical deoxygenation of primary alcohols, Tetrahedron 47 8969 (1991). 

D. H. R. Barton, D. O. Jang, and J. Cs. Jaszberenyi, Radical deoxygenation of secondary and primary alcohols with phenylsilane, Synlett (1991) 435-438. 

Side Note 2.5. Deoxygenation of Primary Alcohols under Tin-free Conditions... 

Aliphatic carboxylic esters have been reduced to produce simple primary alcohols (84-92%) via Cp2TiCl2-catalyzed reaction with Bu MgBr. Additionally, hydrosilylation of aliphatic and aromatic carboxylic esters using Ph2SiH2, (EtO)2Si(Me)H, (EtO)3SiH or MeSiO[Si(Me)H—0]nSiMe3 has been used to produce simple primary alcohols (50-100%). In contrast, the photolytic reactions of esters with HSiCb produces ethers. For example, l-dodecyl acetate was converted into l-dodecyl ethyl ether in this way. Competitive deoxygenation complicates ether formation particularly with secondary and tertiary alkyl esters. All these exotic methods have little synthetic merit. 

J. Dorchak, D. O. Jang, and J. C. Jaszberenyi, The invention of radical reactions. Part XXL Simple methods for the radical deoxygenation of primary alcohols. Tetrahedron 47 8969 (1991). 

Barton, D. H. R., Motherwell, W. B., Stange, A. Radical-induced deoxygenation of primary alcohols. Synf/tes/s 1981,743-745. 

Deoxygenation of the primary alcohol function does not eliminate a chiral centre. For example, the most abundant natural enantiomer of fucose, L-fucose 4.6, is systematically called 6-deoxy-L-ga/acto-hexose. 

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