so heres the entire message.. apparently posted by you rhodium,... but then it was in 1997 so youre forgiven for having a hazy memory
.... ill give the protocol a few tries in nmr tubes ... if successful ill scale up a touch and share my results ... it just seems like a viable method to me... but if you say there are many side reactions then perhaps it is not.... will do a few microscales and get back ... heres the entire post
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Subject: High yield prep of MDP2P from Piperonal
From: rhodium@nym.lycaeum.org
Date: October 02, 1997 at 12:55:30
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When visiting my local university library I found these lab notes on a
crumbled piece of paper lying in a waste basket. It details a high yield
synthesis of MDP2P from piperonal. Peculiar things one can find, indeed.
Preparation of 1-(3,4-methylenedioxyphenyl)-2-nitropropene
15g of piperonal was dissolved in 40ml of MeOH under stirring in
a 250ml Erlenmeyer flask. When all of the piperonal had dissolved, 7.1g
nitroethane was added to the solution. The flask was put in a ice/water
bath with magnetic stirring, and when the temperature of the solution had
dropped to 0°C, a solution of 4g of NaOH in 20ml distilled water (which
had been pre-chilled to 0°C) was added portionwise to the solution, at
such a rate that the temperature never exceeded 15°C. A white precipitate
formed (it may cake in the flask when the temperature drops again, and
must be broken up again with a glass rod or equivalent). The stirring was
continued for one hour, and then 100 ml chilled distilled water was added
to the solution. More of the white precipitate formed. The whole slurry
was poured into a pre-chilled solution of 15ml 30% HCl in 85 ml water in a
500ml Erlenmeyer flask. The flask was swirled gently, and there was slight
bubbling and fizzing, and the color shifted from white to blue to green
to yellow in a minute. Quite spectacular! When the fizzing subsided,
the solution was put back in the ice/water-bath with magnetic stirring.
When the temperature has dropped to about 5°C the solution was clear, with
yellow granules at the bottom. This was the crude product. The solution
was filtered with suction, and the yellow granules was put in a 100ml
beaker, and hot (but not boiling) water was poured over them. The crystals
melted, and unreacted piperonal floated at the surface. The bottom layer,
consisting of the pure nitrostyrene, was collected with a pasteur pipette.
(a disposable plastic pipette was used for this maneuver, in a glass
pipette the nitrostyrene is likely to crystallize. Otherwise, just decant
the water and piperonal from the product). The nitrostyrene was poured on
a watch-glass and was let to crystallize in the refrigerator. The canary-
yellow crystal cake was crushed, and air dried on a filter paper. The
yield was 13.15g, or 67% of theory. This nitrostyrene should be used
within a week, or stored in the cold, as the color fades to a slight
orange over a couple of weeks in room temperature, which is a sign of
decomposition.
Preparation of 1-(3,4-Methylenedioxyphenyl)-2-propanone (MDP2P)
25g (0.12 mols) 1-(3,4-methylenedioxyphenyl)-2-nitropropene was
dissolved in 350ml methanol in a 500ml Erlenmeyer flask situated on a
magnetic stirrer, and chilled to -10°C with an ice/salt bath. Then, with
good stirring, 9.2g (0.24 mols) of NaBH4 was added a little at the time,
not allowing the temperature to rise above 15°C. It fizzes some as the
sodium borohydride dissolves, and the solution will change color. When
the generation of heat had subsided, the ice/salt-bath was taken away
and the solution was allowed to stir at room temperature for two hours.
Then the solution was cooled to 0°C with an ice/salt-bath, and then
125ml 30% hydrogen peroxide was added with good stirring (the exact
concentration of the H2O2 is not critical). With this addition a white,
sticky precipitate formed. 35g potassium carbonate was then added, the
ice bath removed, and the stirring was continued for 18 hours at room
temperature (*). After this time, the solution was transferred to a
1000ml Elenmeyer flask, and slowly acidified with 2M HCl with good
stirring, and care being taken for the evolution of heat and CO2. About
450 ml of acid was needed. The color of the solution turned from a
orange-tinted yellow to a green-tinted yellow at this point. The solution
was checked with pH paper just to be sure. All of the precipitate should
also be gone at this point, if not, continue the stirring for a while.
The solution was divided into two portions of about 500ml each, and each
half was extracted with 3x50ml CH2Cl2, and the pooled extracts (a yellow
solution) was washed with 2x100ml dilute NaOH solution and then 100ml
H2O. The first NaOH wash was deep red, the second one slighty yellow,
and the water was colorless. The organic phase was dried over some
Mg2SO4. The solution was filtered with suction, and the solvent
distilled off at atmospherical pressure. The residue was 21.6g of a
clear yellow oil with a weak smell. The oil was distilled at 2-3 mmHg,
and the product came over at 110-125°C, and the yield was 18 grams of a
water-white oil, or 84% of theory. The oil turned slightly yellow over
the next couple of days, but after that the oil never aquired a deeper
color.
(*) With the addition of K2CO3 and H2O2 the mixture becomes quite thick,
so your magnetic stirrer may not be able to handle it. Use a
mechanical stirrer instead here, or help your poor mag-stirrer for
one or two hours with occasional stirring with a glass rod and
swirling of the flask. Some of the precipitate may cling to the
walls of the flask too, so loosen that up too. In 2-3 hours the
precipitate is much looser, and any mag-stirrer can be used
thereafter.
References:
Step 1: Practical Organic Chemistry, Vogel, 5th Ed.
Pihkal, Shulgin & Shulgin 1991, #100.
Step 2: Synthesis 723-726, July 1994
Pihkal, Shulgin & Shulgin 1991, #109.
Shulgin's yield in the first reaction is 54% and 80% in the second, which
gives an overall yield of 43%. The corresponding yields in this synthesis
is 67% and 84%, and the overall yield is therefore 56%. This synthesis is
also much simpler to carry out, and employs less harsh reaction conditions.
Rhodium
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Replies:
* Re: High yield prep of MDP2P from Piperonal et2o 09:38:32 10/03/97 (0)
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