Antoncho (Official Hive Translator)
02-01-03 22:03
No 403516
      Acids to alcohols: a one(two)-step NaBH4 reduction  Bookmark   

I thought i'd post this, since all traditional methods i've seen involve LAH or some SOCl2....wink

Patent GB795131

47 g. calcium iodide is-dissolved in 30mls tetrahydrofuran the solution cooled with ice water, 0. 38 g. sodium borohydride is added thereto. The mixture is stirred and 1.95 g methyl ethyl ketone or with ethyl acetate the it. The mixture is stirred with the exclusion of moisture for 6 hours while cooled in ice water and is then left to stand for a night at room temperature, then diluted with 50 ml. water, extracted with 5 x 20 ml. ether and the ethereal solution dried over magnesium sulphate. The ether is distilled off, whereby 1. 47 g. p-nitrobenzylalcohol of m. p. 96-97 C. are obtained.

Yield 96%.


0. 55 g. anhydrous calcium chloride is dissolved in 22 ml. ethyl alcohol, the solution cooled to -20 C., 0. 38 g. sodium borohydride is added to same and the reaction mixture is stirred for about 15 minutes. 1. 95g. p-nitro-benzoic acid ethyl ester is then added, the-mixture stirred at'20 C. for a further 3 hours and then slowly-in the course
of-2 hours-warmed ro-5' to-3 C. and stirred at this temperature for a further 2 hours. The mixture is then left to stand overnight at room temperature,then dilutd with 30 ml. water, the alcohol distilled off, the residue diluted with 20 ml. water and shaken with 5 x 20 ml. ether. The ethereal extracts are dried and the ether distilled off. 1. 47 g. p-nitrobenzylalcohol of'm. p. 9597 C. is obtained.

Yield 96%.

10 g. phenylacetic acid ethyl ester is treated
by the method described in Example 10 for 10
hours at 70 C. with-a solution of calcium
borohydride in tetrahydrofuran. After working
up the reduction mixture, beta-phenyl ethanol
is recovered. Yield : 75% ~.

(Chief Bee)
02-02-03 00:40
No 403546
      Nice. The first procedure is somewhat off...  Bookmark   

Nice. The first procedure is somewhat off though, as no starting material is added to the borohydride mixture.
(Official Hive Translator)
02-02-03 04:12
No 403575
      Oooops!  Bookmark   

The original text obviously lacks a line (looked up the pdf!)


But anyway, i'm pleased you consider this 'nice'wink

(Chief Bee)
02-02-03 05:31
No 403585
      Calcium Borohydride  Bookmark   

Many borohydride reagents are useful for COOH -> CH2OH reduction, just not NaBH4 alone. LiBH4 (from LiCl/NaBH4 in THF), as well as NaBH4/I2 and NaBH4/H2SO4, but I haven't posted about any explicit procedures, as I have assumed that the transformation isn't very popular with people here in general, and that these reagents were known to work by those who wanted to do it.

I have never seen Ca(BH4)2 used anywhere before though.
(Hive Bee)
02-02-03 08:35
No 403639
      RE: Reducing Acids to Alcohols in two steps....  Bookmark   

A very good find, some time ago SWIJ had been looking for a way to reduce Phenylalanine carboxyl group and found this article which was made available to SWIJ  by Rhodium, and so SWIJ wants to add to your finding.

Borohydride-Iodine reduction of acids to alcohols (../rhodium/pdf /borohydride-iodine.pdf)

Saludos, from Latin America