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Rhodium please clarify !

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becomezen:
Do you remember Osmium's posts regarding analysis of post-wacker ketone ? I believe he found that it was roughly 85% MD-P2P and 15% MD-P1P ....

So what you are saying here , is that by running the reaction hotter , we can move the gradient even more towards the P2P side (perhaps 95% mdp2p , 5% mdp1p) ??

Also to clarify , the benzoquinone is there to provide oxygen , and bees have claimed success using pure O2...

If that is true , then what are your thoughts about running an O2 wacker even hotter ? I have seen some mention an upper limit of 40° , else the vessel will rupture.....

Assuming you had a vessel that could EASILY withstand the heat and pressure , at what level (temp and pressure) would this reaction be most optimized ?

I ask these questions b/c I have no formal chemistry education , and I am not able to talk "chemistry theory"

Please help !

Thanks  8)

Rhodium:
If that is true , then what are your thoughts about running an O2 wacker even hotter ? I have seen some mention an upper limit of 40° , else the vessel will rupture...

Temp limit: It depends on your vessel. Do not try to heat a vessel not designed for high pressure, or injury will likely result.

Analysis: The O2 wacker of safrole was analyzed by Ritter, not Osmium.

Isomer distribution: The article concerns the wacker oxidations of propenylbenzenes rather than allylbenzenes (as in isosafrole and not safrole itself). To improve the isomer distribution in the case of safrole, perhaps running the reaction cooler is the answer, but to answer that question definitely, someone with a more solid background than myself in physical organic chemistry should probably answer.

NeoSynthesis:
Hiya Bubble - btw.. forgot to thank  you for your much-appreciated detailed reply to my post on Wacker Ox. Anyways.. curious to know if anyones tried this variation, and if so, with what results?

cheers beez

Rhodium:
Novel Palladium Catalytic Systems for Organic Transformations
Takahiro Nishimura, Sakae Uemura
Synlett 201-216 (2004)
DOI:10.1055/s-2004-815412

Abstract
This article summarizes the results of our recent studies on palladium catalytic systems for the oxidation of alcohols and beta­alkenes using molecular oxygen or air together with several successful attempts to make the system recyclable from the viewpoint of ‘green and sustainable chemistry’.


5.0 Palladium(II)-Catalyzed Oxidation of ­Terminal Alkenes to Methyl Ketones Using Molecular Oxygen

Palladium-catalyzed oxidation of alkenes to methyl ketones has been developed in synthetic organic chemistry as well as in industrial processes using PdCl2 and CuCl2 or Cu2Cl2 as catalysts in acidic water under an oxygen atmosphere.23,24 However, this catalytic system is highly corrosive because of its acidic conditions and may cause the formation of chlorinated by-products in some cases. To overcome such drawbacks, halide-free catalytic systems have also been widely investigated.25

On the other hand, Mimoun and co-workers have reported that a Pd(II)-OOH species undergoes an oxygen transfer to terminal alkenes via peroxypalladation to afford methyl ketones as shown in Scheme 12.26


Scheme 12

An example of the palladium-catalyzed oxidation of cyclopentene to cyclopentanone in ethanol using molecular oxygen as the sole reoxidant was reported by Takehira and co-workers in 1985.9a They also proposed the formation of a Pd(II)-OOH species from palladium, ethanol, and oxygen.9a,27

In the course of our studies on the aerobic oxidation of alcohols described in previous sections, we proposed the in situ formation of a Pd(II)-OOH species as well as H2O2. This assumption prompted us to check whether this Pd(OAc)2/pyridine/O2 catalytic system is applicable to the oxidation of terminal alkenes based on Scheme 12.28 In fact, the treatment of 1-dodecene in toluene (5 mL) and 2-propanol (5 mL) in the presence of 5 mol% Pd(OAc)2 and 20 mol% pyridine at 60°C for 6 hours under an oxygen atmosphere afforded the expected 2-dodecanone (70% GLC yield, Scheme 13). Other simple terminal alkenes were converted to the corresponding methyl ketones in good yields under the same conditions. Interestingly, 10-un­decen-1-ol was mainly transformed to 11-hydroxy-2-undec­anone in 71% yield showing that a terminal double bond was oxidized much faster than a hydroxyl group. It is noteworthy that this oxidation system was applicable only to terminal alkenes, and not to internal ones.


Scheme 13

A plausible reaction pathway for this oxidation using Pd(OAc)2/pyridine/2-propanol/O2 catalytic system is shown in Scheme 14, where two catalytic cycles operate. One cycle is the oxidation of 2-propanol (cycle A) to give acetone and a Pd(II)-H species, the latter of which is transformed to a Pd(II)-OOH species by the reaction with oxygen. The Pd(II)-OOH species reacts with an alcohol to give an alkoxypalladium(II) species as well as H2O2.9 This Pd(II)-OOH species also reacts with alkenes via peroxypalladation (Scheme 12) in another catalytic cycle (cycle B) to produce methyl ketones and a Pd(II)-OH species which reacts with H2O2 to reproduce the Pd(II)-OOH species.


Scheme 14



References

[9a] Strucul G. Ros R. Michelin RA. Inorg. Chem. 21, 495 (1982) (See Below)
[9b] Takehira K. Hayakawa T. Orita H. Chem. Lett. 1835 (1985)
[9c] Hosokawa T. Murahashi S.-I. Acc. Chem. Res.  23, 49 (1990) (See Below)

For recent reviews see:
[23a] Tsuji J. Palladium Reagents and Catalysis  Wiley; New York: 1995.  p.19-30 
[23b] Jira R. In Applied Homogeneous Catalysis with Organometallic Compounds   Cornils B. Herrmann WA. VCH; New York: 1996.  p.374-393 
[23c] Monflier E. Mortreux A. In Aqueous-Phase Organometallic Catalysis   Cornils B. Herrmann WA. Wiley-VCH; New York: 1998.  p.513-518 
[23d] Takacs JM. Jiang XT. Curr. Org. Chem. 2003, 7: 369

Recent examples of Wacker oxidation of higher alkenes see:
[24a] Smith AB. Cho YS. Friestad GK. Tetrahedron Lett. 39, 8765 (1998) (See Below)
[24b] Mohammedi O. Chemat F. Brégeault J.-M. Eur. J. Org. Chem. 1998, 1901
[24c] Karakhanov E. Maximov A. Kirillov AJ. Mol. Catal. A: Chem. 2000, 157: 25
[24d] Yokota T. Sakakura A. Tani M. Sakaguchi S. Ishii Y. Tetrahedron Lett. 2002, 43: 8887
[24e] Choi K.-M. Mizugaki T. Ebitani K. Kaneda K. Chem. Lett. 2003, 32: 180

[25a] Bäckvall J.-E. Hopkins RB. Tetrahedron Lett. 1988, 29: 2885
[25b] Bäckvall J.-E. Hopkins RB. Grennberg H. Mader MM. Awasthi AK. J. Am. Chem. Soc. 1990, 112: 5160
[25c] Yokota T. Fujibayashi S. Nishiyama Y. Sakaguchi S. Ishii Y. J. Mol. Catal. A: Chem. 1996, 114: 113
[25d] Kishi A. Higashino T. Sakaguchi S. Ishii Y. Tetrahedron Lett. 2000, 41: 99
[25e] Monflier E. Blouet E. Barbaux Y. Mortreux A. Angew. Chem. Int. Ed., Engl. 1994, 33: 2100
[25f] Monflier E. Tilloy S. Fremy G. Barbaux Y. Mortreux A. Tetrahedron Lett. 1995, 36: 387
[25g] Monflier E. Tilloy S. Blouet E. Barbaux Y. Mortreux A. J. Mol. Catal. A: Chem. 1996, 109: 27
[25h] Hirao T. Higuchi M. Hatano B. Ikeda I. Tetrahedron Lett. 1995, 36: 5925
[25i] Higuchi M. Yamaguchi S. Hirao T. Synlett 1996, 1213
[25j] ten Brink G.-J. Arends IW. Papadogianakis G. Sheldon RA. Chem. Commun. 1998, 2359
[25k] ten Brink G.-J. Arends IW. Papadogianakis G. Sheldon RA. Appl. Catal. A 2000, 194-195: 435
[25l] Ito H. Kusukawa T. Fujita M. Chem. Lett. 2000, 598

[26a] Mimoun H. Charpentier R. Mitschler A. Fischer J. Weiss R. J. Am. Chem. Soc. 102, 1047 (1980) (See Below)
[26b] Roussel M. Mimoun H. J. Org. Chem. 45, 5387 (1980) (See Below)
[26c] Mimoun H. Angew. Chem. Int. Ed. Engl.  21, 734 (1982)

[27] Takehira K. Hayakawa T. Orita H. Shimizu M. J. Mol. Catal. 53, 15 (1989)

[28] Nishimura T. Kakiuchi N. Onoue T. Ohe K. Uemura S. J. Chem. Soc., Perkin Trans. 1, 1915-18 (2000) DOI:10.1039/b001854f (Free!)


[9a]Preparation and oxygen-transfer properties of novel palladium(II) and platinum(II) hydroperoxo and alkylperoxo complexes
Strukul, Giorgio; Ros, Renzo; Michelin, Rino A.
Inorganic Chemistry (1982), 21(2), 495-500 (1982) (https://www.thevespiary.org/rhodium/Rhodium/pdf/pd-pt-hydroperoxo-complexes.pdf)

Abstract
Mononuclear hydroperoxo and tert-butylperoxo complexes RML2OOR1 (L = 1/2 diphosphine or monophosphine; M = Pd, Pt; R = H, Me3C; R1 = activated alkyl) were prepared by condensation reactions of RML2OH with R1OOH. Whereas Me3COOH reacts in all the cases tested, with H2O2 the preparation reaction is sensitive to the nature of R. These compds. behave as typical O-transfer agents, reacting with PPh3, CO, NO, and PhCHO. trans-CF3Pt(PPh2Me)OOCMe3 oxidized terminal olefins to the corresponding Me ketones.
____ ___ __ _

[9c]New aspects of oxypalladation of alkenes
Hosokawa, Takahiro; Murahashi, Shunichi
Accounts of Chemical Research 23(2), 49-54 (1990) (https://www.thevespiary.org/rhodium/Rhodium/pdf/alkene.oxypalladation.pdf)

Summary: A review with 54 refs. dealing with mechanistic and synthetic aspects of intramol. oxypalladation and acetalization of alkenes.
____ ___ __ _

[24a]Convenient Wacker oxidations with substoichiometric cupric acetate
Amos B. Smith, III, Young Shin Cho and Gregory K. Friestad
Tetrahedron Letters 39(48), 8765-8768 (1998) (https://www.thevespiary.org/rhodium/Rhodium/pdf/wacker.o2.cupric.acetate.pdf)
DOI:10.1016/S0040-4039(98)01992-3

Abstract
A modification of the Wacker oxidation of terminal olefins to methyl ketones using substoichiometric amounts of Cu(OAc)2 as a redox shuttle reagent is described. The modified procedure is generally high yielding despite reduced levels of copper salt and convenient. Importantly, in a problematic case, the conditions suppressed acidic hydrolysis during oxidation of substrate (+)-5 containing an acetonide. Has been mentioned in Post 108566 (missing) (dormouse: "improvements in wacker rxn.  -neocelsis", Novel Discourse)
____ ___ __ _

[26a]Palladium(II) tert-butyl peroxide carboxylates. New reagents for the selective oxidation of terminal olefins to methyl ketones.
Mimoun, Hubert; Charpentier, Robert; Mitschler, Andre; Fischer, Jean; Weiss, Raymond
Journal of the American Chemical Society 102(3), 1047-54 (1980) (https://www.thevespiary.org/rhodium/Rhodium/pdf/wacker-pd-h2o2-2.pdf)

Abstract
The synthesis and characterization of new Pd(II) tert-Bu peroxide carboxylates with the general formula [RCO2PdOO-tert-Bu]4 (R = Me, CCl3, CF3, C5F11) are described. X-ray data gave the crystal and mol. structures of [Cl3CCO2PdOO-tert-Bu]4 (I). The 4 Pd atoms of I are coplanar and are located approx. at the corners of a square. Four trichloroacetate bridging anions are alternatively above and below this square. I are highly efficient reagents for the selective stoichiometric oxidation of terminal olefins to Me ketones at ambient temperature, and catalysts for the ketonization of terminal olefins by tert-Bu hydroperoxide. A mechanism involving a 5-membered pseudocyclic peroxymetalation of the coordinated olefin was suggested.
____ ___ __ _

[26b]Palladium-catalyzed oxidation of terminal olefins to methyl ketones by hydrogen peroxide
Roussel, Michel; Mimoun, Hubert
Journal of Organic Chemistry (1980), 45(26), 5387-90 (1980) (https://www.thevespiary.org/rhodium/Rhodium/pdf/wacker-pd-h2o2-1.pdf)

Abstract
Pd(II) complexes are very efficient catalysts or the selective oxidation of terminal olefins RCH:CH2 (R = n-hexyl, n-octyl, n-decyl, AcOCH2) to RCOMe by H2O2. HOCH2CH:CH2 gave a mixture of HCO2H, AcOH, and EtCO2H. This reaction is best carried out in solvents such as tert-BuOH or AcOH, and requires a large excess of H2O2 with respect to the olefin in order to achieve a nearly complete conversion of the substrate without precipitation of metallic Pd. The general trend of this reaction suggested a mechanism very similar to that previously shown for the oxidation of terminal olefins by Pd(II) tert-Bu peroxide carboxylates, and involving a pseudocyclic hydroperoxypalladation of the coordinated olefin.

Scooby_Doo:
GC's of standard benzo DMF wacker showed the reaction to be finished around 3.5 hour mark. There was no yield increase with the extra time. On saying that, it really also depends on what your starting temp is, and how large the reaction. (The larger may be a little quicker due to the higher heat generated by the reaction.)

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