Author Topic: 3-Meo-4-Me-BA Proposal.  (Read 7110 times)

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moo

  • Guest
Dimethyldioxirane articles
« Reply #20 on: September 14, 2004, 02:21:00 AM »
Dioxiranes - Highly Reactive Oxidants for Stereoselective Oxyfunctionalizations
Waldemar Adam, Alexander K. Smerz, Cong-Gui Zhao
J. prakt. Chem. 339, 298-300 (1997)



The following is reference number 9 from the article above.

Epoxidations and Oxygen Insertion into Alkane CH Bonds by Dioxirane Do Not Involve Radical Pathways
Waldemar Adam, Ruggero Curci, Lucia D'Accolti, Anna Dinoi, Caterina Fusco, Francesco Gasparrini, Ralph Kluge, Rodrigo Paredres, Manfred Schulz, Alexander K. Smerz, L. Angela Veloza, Stephan Weinkötz, Roland Winde
Chem. Eur. J. 3(1), 105-109 (1997)



There's more but it remains to be scanned or digged up later. What I found interesting is the fact told in the title of the second reference. They seem to have quite a solid support for their statement. It is still obvious radical pathways aren't excluded if the reaction isn't free of eg. ferrous ions.


amine

  • Guest
Toluene to Tolualdehyde (OTC)
« Reply #21 on: September 14, 2004, 07:27:00 AM »
The proccedure is pretty simple and can be done with fairly good yields.



Step 1. Bromomethylation of toluene.
        This can be done using Paraformaldahyde***, HBr      (produced in-stu via NaBr and H2SO4 and GAA as the solvent.) (87% yield)
        Reference:

Post 475109

(Lego: "Amphetamines/PEAs w/o benzaldehyde or nitroethane", Novel Discourse)


Step 2. Coversion of Toluene to Alcohol (may not be needed).
       I can't seem to find any data, but I'm sure a base-catalysed hydrolysis would remove the bromine group and leave you with a hydroxyl group. NaBr is regenerated (but NaBr is dirt cheap anyway).

Step 3. Oxidation of Benzyl Alcohol via Oxone, NaBr.*
      Proceedure uses NaBr, Oxone and CH3CN for the solvent.
      I assume that NMP** could be used in place (NMP can be distilled out of several paint strippers) It is a polar solvent. (correct me if I'm wrong) (Yield 96%)
      Reference:

https://www.thevespiary.org/rhodium/Rhodium/chemistry/alcohol2aldehyde.oxone-nabr.html



The advantages are that this proceedure is cheap, much cheaper than buying the tolualdahyde.  And toluene ain't that hard to come by. 1 Gallon = $10 dollars?


Does anyone have a reference proceedure for Step 2. I know it should be a relatively easy proceedure.

* There are many other ways to do this Oxidation, DMSO and catalytic HBr could be used. In which case the hydrolysis (Step 2) becomes uncess. It seems though, that yields are higher when oxidation is done w/ the alcohol.
** NMP is found in a 70-85% concentration in some paint strippers.
*** The paraformaldahyde can be replaced by trioxane which are sold as fuel bars.

Post 442563

(Rhodium: "Trioxane as (para)formaldehyde substitute", Methods Discourse)
90g for ~$0.95. Keep in mind the bars must be cleaned. The outside layer needs to be scaped off, and the rest of the bar crushed up and washed with acetone to remove the color.


moo

  • Guest
You could make the last two steps one by using
« Reply #22 on: September 14, 2004, 08:11:00 AM »
You could make the last two steps one by using the Sommelet reaction (hexamethylenetetramine), but with the first reaction one has to be very careful -- bis(bromomethyl)ether is going to form and I assume it is as bad as if not worse than bis(chloromethyl)ether, a violent carcinogen. The latter is formed in mixtures of HCl and formaldehyde. If only it wasn't so...


Nicodem

  • Guest
Cool, benzylic hydroxylation in >90% yield!
« Reply #23 on: September 14, 2004, 07:39:00 PM »
Thanks for the papers, Moo. Too bad they (the 2nd paper) didn't use the in situ method of preparing DMDO, but I think it was only because they were interested in the reaction mechanism and did not use the method for preparative methods. Well, at least the references point to other C-H hydroxylation papers worth checking. The funny thing is that in the same paper we can also find the study of alpha-methyl-styrene epoxidation (two steps in one paper :) ).

I found some other papers on DMDO oxidations and only in one of them there is a case of ring hydroxylation of a reactive aromatic but under special conditions. I still have to read on this potential problem, but even if it turns out that these potential DOM precursors are too sensitive for DMDO, this method would still bee good for preparing P2P from cumene by avoiding the use of Cl2 or Br2 (for those interested in stimulants :( ).

Here is the ref. 9 of the first review in Moo's post. It is a good source on ideas of alternative oxidants useful for benzylic hydroxylation but it is also a thorough selectivity, reactivity and mechanistic study. Apparently there is quite a wide choice of reagents for this oxygen insertion in the tertiary C-H bond.

Tertiary : secondary : primary C-H bond relative reactivity in the one-electron oxidation of alkylbenzenes. A tool to distinguish electron transfer from hydrogen atom transfer mechanisms
Enrico Baciocchi, Francesca D'Acunzo, Carlo Galli and Osvaldo Lanzalunga
J. Chem. Soc., Perkin Trans. 2 (1996) 133


Abstract: Data of tertiary: secondary: primary C-H bond relative reactivity (TSP selectivity) for a number of electron transfer (ET) and hydrogen atom transfer (HAT) reactions of alkylbenzenes have been critically reviewed and in a few cases supplemented by additional experiments. The resulting picture indicates that there are significant differences in TSP selectivity between ET and HAT reactions. When the HAT mechanism is operating the reactivity order tertiary > secondary > primary C-H bond is always observed. This order never holds in reactions occurring by an ET mechanism where, generally, the secondary C-H bond is the most reactive one and the tertiary centre can be either more or even less reactive than the primary one. Whatever the possible reasons for these differences, it turns out that TSP C-H bond selectivity determinations can afford useful information with respect to the distinction between ET and HAT mechanisms in the oxidations of alkylbenzenes. To check this conclusion a study of TSP selectivity in the oxidation of alkylbenzenes promoted by metalloporphyrins and by microsomal cytochrome P-450 has been carried out, which has allowed us to assign a HAT mechanism to these reactions, in full accord with previous attributions.

…and meanwhile novel methods for direct alpha-methyl-styrenes to P2P’s methods continue to pop up:

Post 531247

(psychokitty: "New synthesis of phenylacetones", Novel Discourse)