NaBH 4-BF 3 •Et 2 O, Reduction of carboxylic acid, ester, acid chloride, amide, and nitrile The reduction of aldehydes, ketones and carboxylic acid derivatives to the corresponding alcohols or amines is an important transformation in synthetic organic chemistry. Lithium aluminum hydride and boranes are amongst the most commonly used reagents for this purposes. 1-12 These highly reactive hydrides, however, have severe limitations such as the need for anhydrous solvents, hazardous handling, incompatibility with other functionality, and incomplete reaction. On the other hand, sodium borohydride is more convenient, less expensive, and safer to use, but does not reduce carboxylic acid derivatives, such as nitriles, esters, lactones and amides. 13 To broaden the utility of NaBH 4 , its reactivity has been enhanced with various additives 13,14 including CeCl 3 , 15 CaCl 2 , 16 ZnCl 2 , 17 CuSO 4 , 18 I 2 , 19 BH 3 •Me 2 S, 20 sulfuric acid, 21 catechol, 22 trifluoroacetic acid, 22 sulfur, 23 ZrCl 4 , 24 Et 2 SeBr 2 , 25 methanesulfonic acid, 26 TiCl 4 , 26 Me 3 SiCl, 27 SnCl 2 , 28 MnCl 2 , 29 SmCpCl 2 (THF) 3 , 30 ErCpCl 2 (THF) 3 , 30 Amberlyst-15(H +), 31 Al 2 O 3 , 32 (S)-lactic acid derivatives, 33 (L)-tartaric acid, 34 cobalt complex, 35 (-)-N-dodecyl-N-methyl ephedrenium salt, 36 lanthanoid complexes, 37 Cu 2+-clay/(S)proline, 38 a chiral surfactant, 39 and 3,4,5-trifluorophenylboronic acid. 40 Nevertheless, research in this field is still very active even now. 14 We report herein that carboxylic acids, esters, acid chlorides, amides and nitriles can be reduced directly to the corresponding alcohols or amines using NaBH4/BF3•Et2O in THF. In continuation of our studies on the reactivity of sodium borohydride toward carboxylic acid derivatives, we found that reduction of benzoic acid by NaBH4/BF3•Et2O in THF afforded benzyl alcohol in excellent yield. According to the literature, 3 treatment of sodium borohydride with boron trifluoride etherate afford borane. Although borane is a good reducing agent, it has some drawbacks, such as low boiling points, low spontaneous ignition temperature and toxicity. Thus, NaBH4/BF3•Et3O system is a useful borane source. Pettit, et al. 41 also reported the reduction of tert-butyl 5αpregnane-20S-carboxylate to 20S-tert-butoxymethylene-5αpregnane using this system. Since the reduction of carboxylic acid derivatives, however, by this binary system NaBH4/BF3•Et2O has not been reported, a systematic examination of its scope as a reducing agent using a variety of carboxylic acid derivatives was deemed warranted. The results are summarized in Table 1.