Scooby_Doo
(Hive Bee)
02-02-02 07:14
No 264135
      Ref on Isosafrole to diol via electro
(Rated as: excellent)
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Here is another ref on production of the diol/epoxide form Isosafrole but this time the ref actually used Isosafrole.

Electrochemical Procedure for a Practical Preparation of Piperonal form Isoafrole
J. Org. Chem.  49, 1830-1832 (1984) (../rhodium/chemistry /isosafrole.electro.html)

Experimental Section

Electrolysis of Isosafrole (2). Preparation of 1-[3,4(Methylenedioxy)phenyl]propane-1,2-diol (3a).
A mixture of 2 (100 mg, 0.62 mmol) and NaBr (192 mg, 1.9 mmol) dissolved in MeCN (7 mL) and H20 (3 mL) was electrolyzed in a beakertype undivided cell (3 cm in diameter and 10 cm in height). A constant current (20 mA, 2.83 F/mol) was passed for 140 min by using platinum foils (2 X 1.5 cm2 ) as electrodes and a Metronix Model 543B DC power supply. After the electrolysis at room temperature, 0.5 mL of 1% aqueous H2S04 was added to the mixture, which was stirred for 1 h and neutralized with aqueous NaHCO3. After evaporation of solvents under reduced pressure, the organic substances were extracted with ethyl acetate. The extracts were washed with brine, dried (Na2SO4), and concentrated in vacuo to give a colorless oil, which was chromatographed (Mallinckrodt Silica CC-7 Special), affording 3a (116 mg, 98%) as colorless crystals whose spectral data were identical with those reported.

1-[3,4-(Methylenedioxy)phenyl]-2-propanone (5).
A solution of 3a (100 mg, 0.5 mmol) and p-TsOH (200 mg) dissolved in a distilled benzene (20 mL) was refluxed for 20 min. The usual workup gave 5 (75 mg, 84%)

Nice smile
 
 
 
 
    psychokitty
(Her Majesty, Stoni's Kitty)
02-05-02 20:28
No 265558
      Re: Ref on Isosafrole to diol via electro  Bookmark   

You fucking mean to tell me that this is the first time this reference is posted here at the Hive?  Sheeeeeit!  I've had this reference for over 10 years. 

BTW, this is the reference that details--albeit in limited form--the dehydration of the diol into the ketone using p-toluene-sulfonic acid (as Ritter-ah, SWIM--has done recently).  It's on the last page.  Scooby Doo, where are you?  Could you please type up the relevant experimental information for all of the Hive to see?  Also, don't forget the japanese reference, if only for information's sake.

Thanks.
 
 
 
 
    psychokitty
(Her Majesty, Stoni's Kitty)
02-05-02 20:32
No 265559
      Re: Ref on Isosafrole to diol via electro  Bookmark   

Oh, shit, there it is at the end.  Silly me, I wrote too soon.  Actually, it looks like they didn't use the acid that I was thinking, unless I'm reading it wrong.  Oh well, in one of those french isosafrole articles from way back in 1950 or 60, they synthesize isosafrole through dehydration of the 1-propanol using the p-toluene sulfonic acid and get high yields.  Oh, well.  I guess that is the article that I was thinking about in terms of peculiar acid dehydration methodology. Sorry.
 
 
 
 
    Rhodium
(Chief Bee)
02-06-02 01:29
No 265663
      Re: Ref on Isosafrole to diol via electro  Bookmark   

PK: p-TsOH = para-toluenesulfonic acid

If you have so many references to reactions that aren't already archived on my page, why not submit them - either to me or posting them publicly?

 
 
 
 
    Scooby_Doo
(Hive Bee)
02-06-02 07:17
No 265794
      Re: Ref on Isosafrole to diol via electro  Bookmark   

Hey there Kitty, did you ever get my reply to your 8 step questions?
I wasn't sure if you got it since the Hive got a new home shortly after. I tried PM-ing you awhile ago but the Hive wouldn't let me.

A question for all the Bees who have grasped the electrochemistry much better than I have.

If the above experiment was scaled and speeded up by increasing the amps (the current density?) does this mean the reaction stays essentially the same, or does it mean more chances for side products and/or a totally different reaction?

Is this also true for the wacker type electro reactions which are using an indirect oxidation method rather than a direct oxidation?

 

 
 
 
 
    Scooby_Doo
(Hive Bee)
02-11-02 09:43
No 268004
      Re: Ref on Isosafrole to diol via electro
(Rated as: good read)
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Ok a few things learned from "Laboratory techniques in Electroanalytical Chemistry" by Peter T. Kissinger and Willian R. Heineman.

Selectivity of the reaction can be influenced by the applied electrode potential (potential-controlled reaction), which, in contrast to redox reagents can be varied continuously.

The reation rate can be controlled by the current density.

The turnover degree can be fixed by the charge consumption.

The electrode material and the electrolyte composition can be used as parmeters for controlling the selectivity and reaction rate.