02-01-03 22:03
No 403516
I thought i'd post this, since all traditional methods i've seen involve LAH or some SOCl2....
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%.
EXAMPLE 8.
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% ~.
Antoncho
(Chief Bee)
02-02-03 00:40
No 403546
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
The original text obviously lacks a line (looked up the pdf!)
Sorry.
But anyway, i'm pleased you consider this 'nice'
Antoncho
(Chief Bee)
02-02-03 05:31
No 403585
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
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-
..........java
Saludos, from Latin America