08-05-02 22:43
No 341794
Has anyone other than KrZ and Grouch done a DMF/O2 Wacker? swim would like to give it a shot, but the fact that everyone's going with p-benzo and DMF/O2 is rarely mentioned makes him think maybe there is a problem with the method. SWIM read the writeup on rhodium's site, and it sounds awesome. i mean 75%+ yield, no p-benzo, 1g PdCl2 per 100g safrole. Why don't many people mention it? As for a reactor, one could get a brand new glass 80 psi 2L hydrogenation flask for like $300, one of the ones that uses Ace-Threds. The whole setup w/ oxygen tank would only be like $600-700. SWIM was thinking about it, seeing as a soda bottle is not safe to him. But he don't want to spend all that cash if the reaction isn't as good as it seems. So if anyone out there has done this rxn, please post successes, failures, etc. TFSE has been used, and so far, it doesn't seem to lean towards this rxn.
(Stoni's sexual toy)
08-06-02 00:26
No 341840
A few bees have tried out the MeOH/O2 Wacker. No need for DMF.
Opinions seem to be split about 50:50. Some say it works, others say it doesn't.
I'm not fat just horizontally disproportionate.
(Master Whacker)
08-06-02 09:05
No 342010
(Rated as: excellent)
Those bees who say the O2 Wacker doesn't work must be using really crappy homemade equipment or bad reagents because the reaction works. Period. IPA works better than methanol because less polymerization takes place, however the reaction must be heated slightly or it will take forever to absorb a significant amount of O2. I've seen the nMR's of the ketones produced with the IPA/O2 Wacker and they proved a mixture of 85:15 2-propanone/3-one was present in the ketone fraction of the product. Typical conditions are as follows: 50g alkene/275ml 99%IPA, 1gPdCl2, 2.5g CuCl2 hydrate, temp about 40'C, pressure Max=70PSI recharging vessel when it drops to about 40PSI, agitation provided by Parr shaker.
I'm guessing that many people fail with this reaction because they are not using sufficient agitation to allow proper O2 absorbtion. Yield will be over 70% when good technique and equipment is applied.
(Stoni's sexual toy)
08-06-02 13:39
No 342072
Thank you for the confirmation.
Too bad it took 5 fucking years to finally prove me right!
I'm not fat just horizontally disproportionate.
(Hive Bee)
08-06-02 15:23
No 342094
so how does Isopropanol wackers inhibit polymerization.
As opposed to methanol?
Aren't secondary alcohols less reactive in giving a ketal from an alkene?
I thought methanol was ideal because it formes the ketal at a faster rate than higher alcohols.
(irritable and cranky)
08-07-02 05:42
No 342349
Has anybody tried DMSO, as was mentioned a long time ago, as to it's selectivity like DMF?
DMSO is easy to get, DMF aint.
(Hive Bee)
08-07-02 10:17
No 342405
Ritter, swim don't have a Parr shaker. do you think a large egg stirbar would do the job at 1200 rpm for a small-scale maybe 100g conversion in a 2L vessel? 40 deg. C could be done in an incubator or environmental chamber, no need for heating mantle or hotplate right?
(Newbee)
08-07-02 13:12
No 342449
Put 8 or so inert glass marbles in the reaction vessel,.
This will help cosiderably in intimately combine stuff.
IQ is the rate of logic, as Wisdom increases logic, fear & compromise decrease to reveal objectivity
(Stranger)
08-07-02 21:16
No 342589
Did dmf wacker with 02 twice. failed both times. 02 wacker only failed ~5% of the time. I think it was because of either dirty safrol or running it too short. Must be run for at least 8 to 10 hours minimum. Osmium, did you only just have journal references years ago to go by when doing the wacker? I know the resources probably weren't always readily available back then (depending on how large a city you live in). W/O the hive I would have never expected to be able to do this or never expected there to really be any references easily obtainable.
A recent run with 85ml clear safrol ~1.5-1.75g pdcl2/~8g cucl2 in 320ml MeOH at warm temp for 19 hours pure 02 in 2l pop bottle at 40-50psi. 2ml water. Dont ever go over 40 psi when the bottle gets HOT, guaranteed explosion with elongated bottle. It resulted in 50ml undistilled product that gave 21g mdea. This is the highest yield ever obtained with such a small amount of undistilled product. The sg of the dirty ketone after washes was 1.18g/ml. Use a 2 to 2.5" egg stirbar in a pop bottle. Like ritter says, no heat no uptake, but heat requires special attention with a pop bottle
(Stoni's sexual toy)
08-07-02 23:08
No 342629
> Osmium, did you only just have journal references years
> ago to go by when doing the wacker?
I had only two journal references. One was the original Wacker in H2O, and the other one did it with alcohol solvents. I didn't know about all those other Wacker procedures like benzo, DMF etc.
I'm not fat just horizontally disproportionate.
(Hive Bee)
08-08-02 15:23
No 342979
may have hampered your yeilds.
Too muc chloride ion blocks the palldium by complexing with it.
Try using less CuCl2 next time.
(Hive Bee)
08-23-02 21:13
No 348191
Would it be right to say that the DMF/O2 Wacker, MeOH/O2 Wacker, and IPA/O2 Wacker will ALL work if a good amount of catalyst is used? For example, do you think that most of the failures could have been successes if more PdCl2 had been used. Another question. In the old DMF/O2 Wacker, where the balloon was used and 11 g PdCl2/100 g ketone was used, the safrole was added slowly from a PE addition funnel. Why is it that in the high pressure one this is not called for? Would it work better if it was done? Would the old Wacker work just as well if one were to just dump all the safrole in at once like one does in the new, 35psi one? Also, would running the reaction at a lower temp improve yields? Some say no, some say yes.
(Hive Bee)
08-24-02 00:18
No 348233
I'm confused too, some say don't add water, or that it goes faster if you add a certain amount.
I don't think lowering temperature is going to help your yeilds on the contrary.
If you look at the literature they run it at 50 degress centigrate.
Also they say optimal ratios of PdCl2/CuCl2 is 1/5 mole ratio.
I think the best approach is to read the literature and duplicate what's there, because if you tried what somebody said worked, it's anybody's guess what will happen.