A novel reduction reaction for the conversion of aldehydes, ketones and primary, secondary and tertiary alcohols into their corresponding alkanes Rama D. Nimmagadda and Christopher McRae * Department of Chemistry and Biomolecular Sciences, Division of Environmental and Life Sciences, Macquarie University, Sydney, NSW 2109, Australia Received 21 April 2006; revised 22 May 2006; accepted 1 June 2006 Abstract—A novel one-pot reaction has been developed for the reduction of aldehydes, ketones and primary, secondary and tertiary alcohols into their corresponding alkyl function. This is also the first reported method which can efficiently reduce primary, second- ary, or tertiary alcohols, without affecting carbon–carbon double bonds, into their corresponding alkyl function in high yields. The reduction utilises either diethylsilane or n-butylsilane as the reducing agent in the presence of the Lewis acid catalyst tris(pentafluorophenyl)borane. Ó 2006 Elsevier Ltd. All rights reserved. The reduction of aldehydes, ketones and alcohols to a methyl function is a useful and widely reported synthetic pathway. In the case of ketones and aldehydes, multi- step reduction procedures using reagents such as hydra- zine in basic polyethylene glycol, 1–3 amalgamated zinc in a hydroxylic solvent containing HCl, 4 electrolytic reduc- tion 5 and diphenylsilane at high temperatures 6 have been shown to be quite effective. Single step reductions of a carbonyl function to a methyl group have also been reported using polymethylhydrosiloxane, 7 triethyl- silane 8,9 and triphenylsilane 10 in the presence of tris- (pentafluorophenyl)borane (B(C 6 F 5 ) 3 ). Similarly, the reduction of alcohols to alkanes has also been reported via a range of procedures including acetic acid/HI, 11 mixed hydrides from AlCl 3 and LiAlH 4 , 12 and photo- chemical reduction. 13 However, different reagents/meth- ods are needed depending on whether the substrate is a primary, secondary or tertiary alcohol. For instance, the reduction of primary alcohols to hydrocarbons has been reported using HSiEt 3 in the presence of catalytic amounts of B(C 6 F 5 ) 3 , however, this reagent was unable to reduce secondary and tertiary alcohols to alkanes. 14,15 Primary and secondary acyclic alcohols can be reduced to alkanes using sodium borohydride once they have been activated by triphenylphosphonium anhydride. 16 In addition, aliphatic primary alcohols can be converted into hydrocarbons by condensation with samarium at low temperatures at about 80–90 K. 17 Secondary alco- hols and tertiary alcohols were converted into their corresponding hydrocarbons by hydrogenation in the presence of Ni/Al 2 O 3 catalyst at 190 °C. 18 Catalytic hydrogenation of alcohols to hydrocarbons in the pres- ence of Pd/C was used after first converting the alcohols into ureas using diamines. 19 Chlorodiphenylsilane in the presence of the catalyst, indium trichloride, has been shown to directly reduce benzylic alcohols, secondary alcohols and tertiary alcohols into their corresponding alkanes. 20 In most of these cases, however, carbon–car- bon double bonds are also reduced along with the target carbonyl/alcohol. In this work, we report the direct reduction of primary, secondary and tertiary alcohols, aldehydes and ketones to alkanes using either n-butyl- silane (n-BS) or diethylsilane (DES) as reducing agents. The proposed reaction mechanism for the reduction of alcohols by n-BS is presented in Figure 1. Table 1 con- tains a list of the alcoholic substrates studied, ordered by class. The ability of n-BS and DES to reduce primary alcohols is illustrated with the reduction of phenylmeth- anol 1, and octadecanol 2, using 2 equiv of n-BS or 0040-4039/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.tetlet.2006.06.007 Keywords: Reduction; Aldehydes; Ketones; Alcohols; DES: diethyl- silane; n-BS: n-butylsilane; B(C 6 F 5 ) 3 : tris(pentafluorophenyl)borane. * Corresponding author. Tel.: +61 2 98508288; fax: +61 2 98508313; e-mail: christopher.mcrae@mq.edu.au Tetrahedron Letters 47 (2006) 5755–5758