Author Topic: Replacement of the Hg/Al amalgam reductions?  (Read 14812 times)

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Aurelius

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3-Phenylpropanol US Pat 688359
« Reply #20 on: May 13, 2004, 01:46:00 AM »
US Patent 688359

Improvements in or relating to Method for the Preparation of Aryl Substituted Primary Alcohols

This invention relates to a novel method for the prep of aryl substituted primary alcohols, and pertains more particularly to the preparation of such alcohols by the hydrogenolysis of 4-aryl-1,3-dioxanes.

Ar is an aryl radical, and R is hydrogen or hydrocarbon and may be the same or different.  The 4-aryl-1,3-dioxanes are prepared by reacting formaldehyde with stryrene or substituted styrenes according to the method described by Shortridge, JACS, Vol. 70, p873 (1948).  By the hydrogenolysis of the 4-aryl-1,3-dioxanes there are obtained in extremely high yields and purity, aryl substituted alcohols.  The hydrogenolysis proceedes as depicted below:

Among the 4-aryl-1,3-dioxanes which may be used to give aryl substituted alcohols are included 4-phenyl, tolyl, naphthyl, etc. The preferred dioxanes are those in which each R is hydrogen or a saturated hydrocarbon radical containing from 1-6C.  The hydrogenation is carried out below 200*C. 

Example 1: 3-phenylpropanol

A mixture of 104 pts styrene, 333 pts 37% aq. Formaldehyde, 28.6pts of 96% sulfuric acid is refluxed and stirred for 16 hours.  The org. layer is washed successively with dilute sodium carbonate, sodium bisulfite and water.  The product is dried by azeotropic distillation with 88 pts benzene and vacuum distilled.  90% 4-phenyl-1,3-dioxane  that has BP: 95*C/2mm; Nd25 = 1.5288 and d25 = 1.101

656pts the dioxane above and 132pts of palletized copper chromite are charged into a stainless steel rocking autoclave.  After purging the bomb with hydrogen at 4100 psi the temperature is brought to 175*C for 8 hours.  Then the mix is cooled, washed out with methanol, filtered and distilled.  529pts of 3-phenylpropanol (96%)


Rhodium

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4100 psi??? That would be >250 atm ...
« Reply #21 on: May 13, 2004, 02:15:00 AM »
4100 psi??? That would be >250 atm pressure!


Aurelius

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Hydrogenation
« Reply #22 on: May 13, 2004, 02:31:00 AM »
you don't have to use the hydrogenation procedure given- try a mild procedure and see if the product reduces in the same manner.  If it weren't for the high pressure this is a decent method for obtaining P3Pol.