(Chief Bee)
07-09-03 15:04
No 445851
(Rated as: excellent)
Metal-Catalyzed Epoxidations of Alkenes with Hydrogen Peroxide (Review)
Benjamin S. Lane and Kevin Burgess
Chem. Rev. 103(7) pp 2457 - 2474 (2003) (../rhodium/pdf /metal-cataly
DOI:10.1021/cr020471z
Introduction
Hydrogen peroxide is probably the best terminal oxidant after dioxygen with respect to environmental and economic considerations. Indeed, in certain circumstances, it is better than oxygen insofar as O2/organic mixtures can sometimes spontaneously ignite. As a result, epoxidation systems that use hydrogen peroxide in conjunction with catalytic amounts of cheap, relatively nontoxic metals are potentially viable for large-scale production of inexpensive products, and for specialized applications in development, process, and research. The literature in this area is extensive and difficult to segregate into sharply delineated categories, but a fair way to attempt this is according to the catalyst precursors: "heterogeneous", "soluble metal oxides", and "homogeneous coordination complexes". Organic catalysts designed for asymmetric epoxidation may also function with hydrogen peroxide as a terminal oxidant, but they are beyond the scope of this review. The focus of this review is methods for the production of fine chemicals, but heterogeneous systems (more suitable for production of chemical commodities) are outlined for completeness.
(Hive Addict)
07-10-03 11:00
No 446115
Thanks for the review, Rh. It was a nice read.
Among all things I have read in the review, there was one chapter which asked for more attention than the others, viz. "4.2 Simple metal salts". It mentions that (p 2642) [...] Bicarbonate is an essential component in this transformation. It forms peroxymoncarbonate ion, HCO4-, in this system; the presence of the intermediate was observed using NMR on mixing hydrogen peroxide and HCO3-. Such equilibria had previously been observed by Richardson et al. for formation of HCO4- from hydrogen peroxide and bicarbonate in other solvents 117, and HCO4- without metal was found to be a moderately active epoxidizing agent in aqueous acetonitrile 118.[...]
Peroxymonocarbonate? ... Sodium percarbonate!
http://www.scienceinthebox.com/en_UK/glo
http://www.solvayinterox.com/pcs.htm
I don't think I am unrealistic if I say that SPC - which even most Stimulant forum dwellers can find out to be OTC - might have something to offer us. Maybe a spoontip of the right catalyzing salt and SPC, and there might be no more need for HCOOH/H2O2, or AcOH/H2O2. Who knows...
. SPC is rather useful substance... Post 377353 (GC_MS: "Sodium percarbonate and the Dakin reaction", Novel Discourse).If somebee has access to JACS, would (s)he be so kind to check out references 116 through 119 (from the review), and post them if they are interesting?
Dirty old man
(Chief Bee)
07-12-03 00:25
No 446474
(Rated as: excellent)
A Cheap, Catalytic, Scalable, and Environmentally Benign Method for Alkene Epoxidations
Benjamin S. Lane and Kevin Burgess
J. Am. Chem. Soc. 123(12), 2933-2934 (2001) (../rhodium/pdf /epoxidation.
DOI:10.1021/ja004000a
Bicarbonate Activation of Hydrogen Peroxide: Oxidation of Sulfides by Peroxymonocarbonate
David E. Richardson, Huirong Yao, Karen M. Frank, and Deon A. Bennett
J. Am. Chem. Soc. 122(8), 1729-1739 (2000) (../rhodium/pdf /peroxymonoca
DOI:10.1021/ja9927467
Epoxidation of Alkenes with Bicarbonate-Activated Hydrogen Peroxide
Huirong Yao and David E. Richardson
J. Am. Chem. Soc. 122(13), 3220-3221 (2000) (../rhodium/pdf /epoxidation.
DOI:10.1021/ja993935s
Manganese-Catalyzed Epoxidations of Alkenes in Bicarbonate Solutions
Lane, B. S.; Vogt, M.; DeRose, V. J.; Burgess, K.;
J. Am. Chem. Soc. 124(40), 11946-11954 (2002) (../rhodium/pdf /epoxidation.
DOI:10.1021/ja025956j
Supplementary Information (http://pubs.acs.org/subscribe/journals/
(Hive Addict)
07-12-03 17:56
No 446630
(Rated as: excellent)
Thank you for the refs, Rh. Manganese-Catalyzed Epoxidations of Alkenes in Bicarbonate Solutions looked really interesting...
And my suspicions about SPC (sodium percarbonate) being useful in the peracid oxidation of alkenes proved to be right! I found the following interesting article:
Dissociation of hydrogen peroxide adducts in solution: the use of such adducts for epoxidation of alkenes.
A M d'A Rocha Gonsalves et al.
J Chem Res (M) (1991) 2101-2118.
Abstract - Solid adducts of hydrogen peroxide, when stirred with various solvents; provide eauilibrium concentrations of anhydrous H2O2. The position of equilibrium is dependent on both the nature of the solvent and that of the adduct, so that controlled release of anhydrous H2O2 into solution can be arranged through proper choice of solvent and adduct. As one example of the advantage of such adducts, they have been used, in the presence of trichloroacetonitrile, carboxylic acid chlorides, imidazolides and anhydrides, as convenient means of epoxidising alkenes.
Experimental
Preparation of adducts of H2O2: SPC and urea.H2O2 were obtained commerially (Interox Chemicals, Widnes, UK) but can be synthesised readily [2]. The adduct of H2O2 with triphenylphosphine oxide was prepared from triphenylphosphin and a 30% (w/v) aqueous solution of H2O2 [2].
Use of H2O2 adducts in epoxidation:
(i) with carboxylic acid chlorides - A mixture of the acid chloride (2.2 mmol), alkene (1 mmol), imidazole (1.1 mmol) and tridecane (0.54 mmol, IS) in dry CHCl3 (6 mL), was stirred at room temperature, under nitrogen. The adduct (2.6 mmol as H2O2) was added in one portion. For larger scale reactions, the IS (tridecane) was omitted. For example: cyclooctene (1.5 mL) was dissolved in CHCl3 (60 mL) and reacted with p-nitrobenzyl chloride (4 g), imidazole (0.78 g) and urea.H2O2 adduct (2.2 g) with stirring for 24 hourse at 32°C. The resulting solution was washed with water, aqueous sodium hydroxide, dilute aqueous HCl and water again before being dried (Na2SO4). Evaporation of solvent gave the epoxide, bp 90°C/20 mmHg (1.15 g; 77% yield).
(ii) with p-nitrobenzoyl imidazolide - A mixture of the alkene (1 mmol), N-p-nitrobenzoylimidazolide (2.2 mol), imidazole (0.25 mol) and tridecane (0.6 mol; IS) in dry CHCl3 (8 mL) was stirred under nitrogen at room temperature. The adduct (2.2 mole as H2O2) was added in one portion.
(iii) with carboxylic acid anhydrides - A mixture of the alkene (1 mmol), imidazole (1 mmol), acetic anhydride (2.3 mole) and tridecane (0.54 mole) in CHCl3 (6 mL) was stirred at room temperature. The adduct (2.3 mmole as H2O2) was added in one portion. Limonene in 3 hours gave 95% of the three possible epoxides (obtained in the ration 1,2-mono : 9,10-mono : 1,2-9,10-bis-epoxide = 64:30:1). In a typical larger scale experiment, α-pinene (1.8 mL) in CHCl3 (60 mL) was reacted with acetic anhydride (2.5 mL), imidazole (0.78 g) and urea.H2O2 adduct (2.2 g), with stirring at room temperature for 3 hours at 22°C. The resulting solution was washed with aqueous sodium bisulphite and water and then dried. Evaporation of the solvent gave a residue which was distilled, bp 35°C/2 mmHg, to give 1.36 g (78% yield) of α-pinene epoxide. The structure of the epoxide was confirmed by comparison of its 1H-NMR spectrum and GC retention time with an authentic sample.
(iv) with nitriles (Payne reaction) - A mixture of the alkene (1 mmol), imidazole (1.3 mmol), trichloroacetonitrile (0.75 mL, 7 mmol) and tridecane (0.54 mmol; IS) in DCM (20 mL, saturated with water) was stirred at room temperature and the adduct (2.7 mmol as H2O2) was added in one portion. With 1-methylcyclohexene and 2,3-dimethylbut-2-ene, Ph3PO.½H2O2 was used in dry DCM. With limonene, the three possible epoxides were obtained in the yields given: (a) urea.H2O2 gave 1,2-mono (72%), 9,10-mono (3%), 1,2-9,10-bis (7%); (b) Na2CO3.1½H2O2 gave 1,2-mono (82%), 9,10-mono (3%), 1,2-9,10-bis (6%); (c) Ph3PO.½H2O2 gave 1,2-mono (73%), 9,10-mono (13%), 1,2-9,10-bis (13%). With cyclohexene or cyclooctene, yields of over 80% could be achieved over extended reaction times but repeated additions of adducts were necessary during the course of reaction. With 1-octene, no reaction was observed in 24 hours at room temperature or at 35-40°C.
Preparation of p-nitrobenzoylimidazolide: To a solution of p-nitrobenzoyl chloride (9.5 g; 0.05 mol) in dry THF (100 mL) was added dropwise with stirring a soltion of imidazole (7.0 g; 0.11 mole) is a dry THF (50 mL) over a period of 10 minutes at room temperature. The solution was left to stir for a further 30 minutes, after which the solution was filtered and evaporated to give the pale yellow p-nitrobenzoylimidazolide (10.0 g; 92% yield), mp 122-122.5°C (cyclohexane, lit mp 120-122°C [11]).
References
[2] AA Oswald et al. JOC 28 (1963) 651 [urea.H2O2]; RD Temple et al. JOC 28 (1963) 2495 [Ph3PO.½H2O2]; DP Jones et al. JCS Dalton Trans (1980) 1526 [Na2CO3.1½H2O2].
[11] JP Klinman et al. JACS 90 (1968) 4390.
Table: some epoxidations of alkenes with adducts of hydrogen peroxide and various activated acyl compounds a or nitriles b
| ACYL COMPOUND OR NITRILE | ALKENE | ADDUCTc | TIME (HR) | YIELD OF EPOXIDEd |
| p-O2NPhCOCl | cyclo-C8H14 | SPC | 3 | 92 |
| " | U | 3 | 75 + (13)e | |
| " | PO | 1 | 25 + (75)e | |
| 1-octene | U | 60 | 0 + (64)e | |
| 1-octene | SPC | 23 | 24 + (4)e | |
| CH3COCl | trans-4-octene | U | 3 | 4 + (92)e,i |
| cyclo-C8H14 | U | 1 | 73 + (17)e,i | |
| N-p-O2NPhCOImf | cyclo-C8H14 | U | 1.5 | 87 |
| " | PO | 1 | 79 | |
| (CH3CO)2O | cyclo-C8H14 | U | 5 | 95 |
| " | SPC | 22 | 96 | |
| " | PO | 3 | 98 | |
| 1-octene | U | 30 | 89 | |
| trans-4-octene | U | 6 | 93 | |
| 2,3-dimethylbut-2-ene | U | 1 | 89 | |
| limonene | U | 3 | 95g | |
| α-pinene | U | 3 | 78 | |
| 1-methylcyclohexene | U | 4 | 85 | |
| (CF3CO)2O | cyclo-C8H14 | U | 3 | 33 + (2)h |
| " | U | 0.5 | 74 + (14)i | |
| Cl3CN | 1-methylcyclohexene | U | 0.3 | 92 |
| " | SPC | 5 | 92 | |
| " | PO | 0.08 | 87 | |
| 2,3-dimethylbut-2-ene | U | 0.25 | 97 | |
| " | SPC | 0.5 | 96 | |
| " | PO | 0.02 | 100 | |
| limonene | U | 1 | 82g | |
| " | SPC | 5.5 | 91g | |
| " | PO | 0.08 | 99g | |
| cyclohexene | U | >24 | >80j | |
| cyclo-C8H14 | U | >24 | >80j |
(a) - The activated acyl compounds are: acyl chlorides, N-acylimidazolides and carboxylic acid anhydrides. Experimental details are given in the text.
(b) - The nitrile was usually Cl3CN.
(c) - SPC = Na2CO3.1½H2O2; U = H2NCONH2.H2O2; PO = Ph3PO.½H2O2.
(d) - These yields were determined by GC by reference to an internal calibration standard. Usually no other products were observed.
(e) - The percentage yields shown in parentheses are due to chlorohydrins produced by epoxide ring opening. Total yield of alkene oxidation is obtained by addition of this percentage to that of the epoxide.
(f) - Im = imidazole residue
(g) - 1,2; 9,10- and 1,2-9,10-epoxide isomers are produced but mainly 1,2-
(h) - This experiment was done with imidazole present, the yield is poor compared with that done in its absence (i).
(i) - Imidazole was left out of the reaction mixture.
(j) - Reaction did not stop at 80% yield if more adduct was added. The relatively slow reaction makes it wasteful of oxidant.
Dirty old man
(Chief Bee)
07-12-03 22:11
No 446676
These epoxidations, especially the last one, shows a lot of promise for our purposes - styrene being epoxidized in close to quantitative yield using aqueous bicarbonate and hydrogen peroxide with a little MnSO4 as catalyst, which in turn is easily made from KMnO4, just substitute the acetic acid with H2SO4 in my archived preparation of manganous acetate (../rhodium /mangan
Possibly the reaction can be performed in a dual-phase setup, with the alkene in a DCM phase and the inorganics in an aqueous phase if a PTC is added - the great thing about the DCM being that it will automatically act as a heatsink, carrying away the heat from the exothermic reaction by boiling, thus keeping the reaction relatively cool even if the hydrogen peroxide is added relatively quickly (and not over 36h as they currently do on a full molar scale).
(Chief Bee)
07-12-03 22:42
No 446683
(Rated as: excellent)
GC_MS - as you are so interested in percarbonate and epoxidations, do you have these articles?
Sodium Percarbonate (SPC) As A Hydrogen Peroxide Source For Organic Synthesis
Chem. Lett. 665-666 (1986)
Abstract: Sodium percarbonate (SPC) is an inexpensive, stable, safe and commercially available material which may be used as a hydrogen peroxide source for organic synthesis. Epoxidation, amine and sulfide oxidation reactions were simply performed with the solid reagent in moderate to excellent yield.
Sodium Perborate and Sodium Percarbonate in Organic Synthesis
Synthesis 1325-1347 (1995)
Abstract: This article reviews the oxidation of organic compounds carried out with either sodium perborate or sodium percarbonate as an oxygen source. Special attention is drawn to the differences in results provided by these two oxidants and to the influence of experimental conditions.
Sodium perborate and sodium percarbonate: further applications in organic synthesis
Alexander McKillop and William R. Sanderson
J. Chem. Soc., Perkin Trans. 1, 2000, (4), 471 - 476 (Free access!)
DOI:10.1039/a804579h
Abstract: Review of the literature covering the years 1995 to 1998.
(Hive Addict)
07-13-03 19:13
No 446838
(Rated as: excellent)
I don't have the Chem Lett reference, but it is not that hard to acquire.
If you would have read the Addendum during correction from the Synthesis article, you would have found an equally interesting sodium percarbonate (SPC) / sodium perborate (SPB) review:
A McKillop, W R Sanderson. Sodium perborate and sodium percarbonate: cheap, safe and versatile oxidising agents for organic synthesis. Tetrahedron 51(22) (1995) 6145-6166. DOI:10.1016/0040-4020(95)00304-Q
This review is complementary to the one published in Synthesis, and for sure is a must-read as well.
My interest was usually in SPB, and not SPC, because it was easier to get this compound in smaller quantities. I was unable to locate a company which wanted to deliver me less than 1 m3 SPC, or didn't make a 100x profit on the substane.
Useful SPB references in my collection:
1. Alexander McKillop, J A Tarbin. Functional group oxidation using sodium perborate. Tetrahedron 43(8) (1987) 1753-1758. DOI:10.1016/S0040-4020(01)81484-8
Abstract - Sodium perborate in acetic acid is an effective reagent for the oxidation of anilines to nitroarenes and of sulphides to either sulphoxides or sulphones. it is also an excellent reagent for the oxidative deprotection of ketone dimethylhydrazones. Baeyer-Villiger oxidation of ketones can be carried out with sodium perborate in either trifluoroacetic acid or acetic acid/trifluoroacetic acid mixtures, and hydroquinones and certain highly substituted phenols are smoothly converted into quinones.
2. Alexander McKillop, Duncan Kemp. Further functional group oxidations using sodium perborate. Tetrahedron 45(11) (1989) 3299-3306. DOI:10.1016/S0040-4020(01)81008-5
Abstract - Sodium perborate in acetic acid is an effective reagent for the oxidation of aromatic aldehydes to carboxylic acids, iodoarenes to (diacetoxyiodo)arenes, azines to N-oxides, and various types of sulphur heterocycles to S,S-dioxides. Nitriles are unaffected by the reagent in acetic acid, but undergo smooth dehydration to amides when aqueous methanol is employed as solvent.
3. Amalendu Banerjee, Banasri Hazra, Atashi Bhattacharya, Santanu Banerjee, Gopal C Banerjee, Saumitra Sengupta. Novel application of sodium perborate to the oxidation of aromatic aldehydes, α-hydroxycarboxylic acids, 1,2-diketones, α-hydroxyketones, 1,2-diols and some unsaturated compounds. Synthesis (1989) 765-766.
Abstract - Sodium perborate in acetic acid at 95°C oxidizes aromatic aldehydes, α-hydroxycarboxylic acids, 1,2-diketones, benzoin, 1,2-diols and some unsaturated compounds.
4. Gaoyang Xie, Linxiao Xu, Jun Hu, Shiming Ma, Wei Hou, Fenggang Tao. Sodium perborate oxidations of cyclic and acyclic alkenes to oxiranes or vicinal acetoxy alcohols. Tetrahedron Letters 29(24) (1988) 2967-2968. DOI:10.1016/0040-4039(88)85059-7
Abstract - Under different reaction conditions, sodium perborate/acetic anhydride oxidized alkenes into oxiranes or vicinal acetoxy alcohols in good yields.
5. Pakawan Nongkunsarn, Chistopher A Ramsden. Oxidative rearrangement of imines to formamides using sodium perborate. Tetrahedron 53(10) (1997) 3805-3830. DOI:S0040-4020(97)00101-4
6. Didier Roche, Kapa Prasad, Oljan Repic, Thomas J Blacklock. Mild and regioselective oxidative bromination of anilines using potassium bromide and sodium perborate. Tetrahedron Letters 41 (2000) 2083-2085. DOI:10.1016/S0040-4039(00)00119-2
Abstract - The selective monobromination of various deactivated anilines using potassium bromide and sodium perborate as oxidant has been achieved. The use of ammonium molybdate as catalyst accelerates the rate of reaction but is not essential to obtain good yields and high selectivities.
7. G W Kabalka, K Yang, N K Reddy, C Narayana. Bromination of alkenes using a mixture of sodium bromide and sodium perborate. Synthetic Communications 28(5) (1998) 925-929.
Abstract - Bromination of alkenes with sodium bromide in the presence sodium perborate provides a simple, high yield route to dibromoalkanes.
8. B P Bandgar, Miss Neeta J Nigal. Regioselective catalytic halogenation of aromatic substrates. Synthetic Communications 28(17) (1998) 3225-3229.
Abstract - Regioselective chlorination and bromination of some aromatic substances have been carried out using KCl and KBr in presence of sodium perborate as an oxidant and sodium metavanadate, sodium tungstate, ammonium metavanadate and ammonium molybdate as efficient catalysts. This environmentally friendly catalytic halogenation method gave good yields of products under mild conditions.
Except for the McKillop review and the imine>formamide rearrangement article, all articles can be req'd.
Some notes: The Kabalka article can be applied on propenylbenzenes to yield their dibromo derivatives (tested in the lab). I tried a iodination as well, but the end product was not purified nor analysed. However, upon addition of KI to the acetic acid/SPB mixture, there was an immediate formation of I2 (colour) and heat.
The Xie article has been evaluated a loooong time ago (before I found this board) and seems to work as well. I used Ac2O as reactant/solvent though, so I don't know how many bees are waiting for this adaptations. Reaction was over very quickly though. The method is solvent sensitive. DCM, for instance, has been tested and failed. Usually, acetic acid or acetic anhydride (or trifluoro analogues) are involved.
Dirty old man
(Chief Bee)
07-13-03 21:12
No 446865
(Rated as: excellent)
Here is the review from Tetrahedron. I didn't download the imine to formamide article, as it only concerned aromatic imines, and used trifluoroacetic acid as solvent.
Sodium perborate and sodium percarbonate: cheap, safe and versatile oxidising agents for organic synthesis. (Review)
A McKillop, W R Sanderson
Tetrahedron 51(22), 6145-6166 (1995) (../rhodium/pdf /perborate-pe
DOI:10.1016/0040-4020(95)00304-Q
(Chief Bee)
07-27-03 10:19
No 450112
(Rated as: good read)
As mentioned in Post 446838 (GC_MS: "SPC/SPB", Novel Discourse):
Sodium perborate oxidations of cyclic and acyclic alkenes to oxiranes or vicinal acetoxy alcohols
Gaoyang Xie, Linxiao Xu, Jun Hu, Shiming Ma, Wei Hou, Fenggang Tao
Tetrahedron Letters 29(24), 2967-2968 (1988) (../rhodium/pdf /perborate-ep
DOI:10.1016/0040-4039(88)85059-7
Abstract
Under different reaction conditions, sodium perborate/acetic anhydride oxidized alkenes into oxiranes or vicinal acetoxy alcohols in good yields.
(Hive Addict)
09-30-03 08:54
No 461804
(Rated as: good read)
In Post 446630 (GC_MS: "SPC alkene oxidation", Novel Discourse), they didn't use solely SPC but also urea-hydrogen peroxide for alkene epoxidation purposes. Here is an article describing the synthesis of urea.H2O2.
G S Patil, G Nagendrappa. Epoxidation of cyclic vinylsilanes by urea-hydrogen peroxide complex.
Synthetic Communications 32(17) (2002) 2677-2681. (../rhodium/djvu /patil.djvu)
DOI:10.1081/SCC-120006032
[...]
Preparation of urea-hydrogen peroxide complex (UHP)
Urea (65 g, 1.08 mol) was dissolved in 100 mL water of 30% w/v of H2O2 (0.88 mol) by warming to 40°C on a water bath. The resultant clear solution was cooled to 5-10°C for 30 min, when white crystals of UHP precipitated, which were filtered and air dried overnight. The complex was further dried oon P2O5 in a vacuum desiccator and stored in a refrigerator; yield, 34 g (41% based on H2O2 used); mp 90-92°C (Lit mp 90-93°C). The dry UHP complex was found to be >98.5% pure on the basis of molar ration of H2O2 and urea as estimated by iodimetric titration method using standard sodium thiosulfate solution.
And yes, the SPC epoxidation method is being tested
.
Advanced clitoris massage specialist. 32 years of experience. PM me for a "sample".
(Hive Bee)
09-30-03 21:28
No 461934
(Rated as: good read)
The Urea-Hydrogen Peroxide Complex: Solid-State Oxidative Protocols for Hydroxylated Aldehydes and Ketones (Dakin Reaction), Nitriles, Sulfides, and Nitrogen Heterocycles.
Varma, Rajender S.; Naicker, Kannan P.
Organic Letters (1999), 1(2), 189-191
DOI:10.1021/ol990522n
CAN 131:102060, AN 1999:334353
An efficient solid-state oxidn. of org. mols. is described using a stable, inexpensive, and easily handled reagent, the urea-H2O2 adduct. The generality of the reaction was demonstrated in oxidn. of several mols., hydroxylated aldehydes and ketones (to hydroxylated phenols), sulfides (to sulfoxides and sulfones), nitriles (to amides), and N heterocycles (to N-oxides).
Asymmetric epoxidation of enones employing polymeric a-amino acids in non-aqueous media.
Bentley, Paul A.; Bergeron, Sophie; Cappi, Michael W.; Hibbs, David E.; Hursthouse, Michael B.; Nugent, Thomas C.; Pulido, Rosalino; Roberts, Stanley M.; Wu, L. Eduardo.
Chemical Communications (Cambridge) (1997), (8), 739-740
CAN 127:34072, AN 1997:330663
Urea-hydrogen peroxide complex in an org. solvent and in the presence of DBU and poly-(L)-leucine causes rapid asym. epoxidn. of the enones R1CH:CHCOR2 (R1 = R2 = Ph; R1 = CH:CHPh, R2 = 2-naphthyl; R1 = Ph, R2 = Me2CH, Me).
A very simple oxidation of olefins and ketones with UHP [urea-hydrogen peroxide] - maleic anhydride.
Astudillo, Luis; Galindo, Antonio; Gonzalez, Antonio G.; Mansilla, Horacio.
Heterocycles (1993), 36(5), 1075-80
CAN 119:202722, AN 1993:602722
The oxidn. of olefins and ketones to oxiranes and esters, resp., is carried out with the UHP (urea-hydrogen peroxide complex)-maleic anhydride system in a mild and very simple procedure. Byproducts urea and maleic acid are readily removed by filtration.
Enantioselective epoxidation of non-functionalized alkenes using a urea-hydrogen peroxide oxidant and a dimeric homochiral Mn(III)-Schiff base complex catalyst.
Kureshy, Rukhsana I.; Khan, Noor-ul H.; Abdi, Sayed H. R.; Patel, Sunil T.; Jasra, Raksh V.
Tetrahedron: Asymmetry (2001), 12(3), 433-437
DOI:10.1016/S0957-4166(01)00057-X
CAN 135:107192, AN 2001:259373
The catalytic enantioselective epoxidn. of chromenes, indene and styrene using a urea-hydrogen peroxide adduct as an oxidizing agent and a novel dimeric homochiral Mn(III)-Schiff base catalyst has been investigated in the presence of carboxylate salts and nitrogen and oxygen coordinating co-catalysts. Conversions of >99% were obtained with all alkenes except styrene. Abs. chiral induction, as detd. by 1H NMR using the chiral shift reagent (+)-Eu(hfc)3, was obtained in the case of nitro- and cyanochromene. The catalyst could be re-used for up to five cycles with some loss of activity due to degrdn. of the catalyst under epoxidn. conditions with retention of e.e.'s.
A Dream Within A Dream (http://www.poedecoder.com/Qrisse/works/
(Hive Addict)
02-20-04 20:17
No 490021
(Rated as: excellent)
Oxidation Reactions Using Urea-Hydrogen Peroxide; A Safe Alternative to Anhydrous Hydrogen Peroxide
Mark S. Cooper*, Harry Heaney, Amanda J. Newbold, William R. Sanderson
*Department of Chemistry, Loughborough University of Technology, Leicestershire, LE11 3TU, England
Synlett (1990) p. 533-535
http://www.geocities.com/phorkys_hecate/
DOI:10.1055/s-1990-21156
Abstract
Urea-hydrogen peroxide (UHP) alone or in combination with carboxylic anhydrides has been shown to serve as a valuable alternative to anhydrous hydrogen peroxide: the range of substrates oxidised include alkenes (epoxidation), ketones (Baeyer-Villiger reaction), sulphides (to sulphones), nitrogen heterocycles (to N-oxides), and aromatic hydrocarbons (to phenols).
Related posts
Post 488372 (Rhodium: "Aromatic Iodination with I2 and Urea-H2O2 (UHP)", Chemistry Discourse)
Post 461934 (Vitus_Verdegast: "More data on urea.H2O2", Novel Discourse)
Post 461804 (GC_MS: "Urea-Hydrogen peroxide complex", Novel Discourse)
Post 459094 (java: "Re: Novel easy preparations of Iodobenzene.....", Novel Discourse)
Post 446630 (GC_MS: "SPC alkene oxidation", Novel Discourse)
Post 435890 (Lego: "Oxidation of oximes to nitroalkanes", Chemistry Discourse)
Post 400186 (Bubbleplate: "Some Research Starting Points", Methods Discourse)
Post 280649 (halfapint: "Re: Acetate of Manganese", Novel Discourse)
I'd be glad to type the article up if someone wants, but I can't now as I have very little free time for the moment
http://www.movieconnection.it/schede/nos
(Chief Bee)
03-03-04 00:07
No 492477
(Rated as: excellent)
A simple and efficient method for epoxidation of terminal alkenes
C. Copéret, H. Adolfsson and K. B. Sharpless
J. Chem. Soc. Chem. Commun. 1565-1566 (1997) (../rhodium/pdf /terminal.epo
Abstract
The use of a catalytic amount of 3-cyanopyridine in the methyltrioxorhenium catalysed epoxidation of terminal alkenes with aqueous hydrogen peroxide speeds turnover, which results in the formation of many functionalized epoxides in high yields.
Representative procedure for the epoxidation of terminal alkenes:
A mixture of dec-1-ene (28.0 g, 200 mmol), 3-cyanopyridine (2.08 g, 20 mmol) and MTO (249 mg, 1 mmol) in CH2Cl2 (120 ml) was treated with 40 ml of 30% oxygen evolution ceased (1 h). Following phase separation, the water layer was extracted with CH2Cl2, the combined organic layers were dried over Na2SO4 and concentrated to an oil. Hexane was added to this crude product, and the resulting white precipitate was removed by filtration. The filtrate was concentrated, and the crude colourless oil was distilled to yield 31.4 g of decene oxide (94% yield, 96.5% purity).
In summary, a remarkable, albeit poorly understood, beneficial effect of 3-cyanopyridine on MTO-catalysed epoxidations of terminal alkenes has been established. For this challenging class of substrates, this method of epoxidation could prove to be one of the most convenient because:
(i) it shows good functional group compatibility (wide scope)
(ii) it is mild (i.e. neutral conditions, room temperature)
(iii) it uses a readily available, safe and environmentally friendly oxidizing agent (30% aqueous H2O2)
(iv) it is easy to perform on the scales common (1 to 200 mmol) in the laboratory (no tedious work-up, no by-products).
The Hive - Clandestine Chemists Without Borders
(Chief Bee)
06-08-04 19:25
No 512218
(Rated as: good read)
Highly selective epoxidation of alkenes and styrenes with H2O2 and manganese complexes of the cyclic triamine 1,4,7-trimethyl-1,4,7-triazacyclononane
Dirk De Vos and Thomas Bein
JCS Chem. Commun. 917-918 (1996) (../rhodium/pdf /www.rhodium.
Abstract
In acetone and at subambient temperatures, manganese complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane catalyse the selective oxidation of many alkenes and styrenes to epoxides with an efficient use of H2O2; the regio- and chemo-selectivity resemble those of manganese–porphyrin catalysts.
The Hive - Clandestine Chemists Without Borders
(Chief Bee)
11-03-04 07:31
No 539383
(Rated as: good read)
Manganese catalysts in homogeneous oxidation reactions
Jelle Brinksma, Thesis, Univ. Groningen (2002) (http://www.ub.rug.nl/eldoc/dis/science/
Table Of Contents
- Introduction Oxidation Catalysis
- Manganese Complexes as Homogeneous Epoxidation Catalysts
- In Situ Prepared Manganese Complexes as Homogeneous Catalysts for Epoxidation Reactions with Hydrogen Peroxide
- Homogeneous cis-Dihydroxylation and Epoxidation of Olefins with High Hydrogen Peroxide Efficiency by Mixed Manganese/Activated Carbonyl Systems
- Manganese Catalysts for Alcohol Oxidation
- New Ligands for Manganese Catalysed Selective Oxidation of Sulfides to Sulfoxides with Hydrogen Peroxide
- Conclusions and Future Prospects
The Hive - Clandestine Chemists Without Borders