Lego
(Stranger)
03-31-03 23:56
No 422851
      Oxidation of Amines to Aldehydes on Clay with...
(Rated as: excellent)
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Oxidation of Amines to Aldehydes on Clay with Cu(II)-NO3/H2O2 under solvent-free microwave conditions

The reference for this article was found on Rhodium's (../rhodium/chemistry /mw.clays.txt) page:
Check out ref. 16 for the conversion of phenyl acetic acids to benzaldehydes or conversion of phenethylamine to phenylacetaldehyde

Already mentioned by Post 400186 (Bubbleplate: "Some Research Starting Points", Methods Discourse):
General Oxidation Reaction-Claycop [Copper(II) nitrate/Clay]/H2O2: Tetrahedron Lett.,39, 1307 (1998)

Post 417460 (Sunlight: "Oxydation of tryptamine", Novel Discourse):
Sunlight: Please post details of the procedure of oxydation of amines to ketones, it could be used to oxidize tryptamine into indol 3 acetaldehyde, then easily converted to DMT or other with NaBH4 reductive amination .




Here we go:

Tetrahedron Letters, 1998, 39, 1307-1308

[...]

The experimental procedure involves a simple mixing of neat substances with claycop (0.46 g per mmol of the substrate) followed by the addition of 30% H2O2 (0.1 mL) in an open container. The mixture is placed in an alumina bath inside a microwave oven and is irridating for 15-90 sec in the solid state. Upon completion of the reaction, monitored on TLC (hexane:AcOEt, 10:1), the product is extracted into methylene chloride and solvent removed to afford pure products.

R1R2CHR3 --> R1R2C=O
Entry;R1;R2;R3;Mole Ratioa;Time (sec); Yield(%)
1;C6H5;H;COOH;1:0.8:1;60;83
2;C6H5;C6H5;COOH;1:0.8:1;90;82
3;C6H5;H;CN;1:1.6:2b;45;80
4;C6H5;H;NH2;1:0.8:1;30;76
5;C6H5;H;Br;1:0.8:1;30;75
6;p-NO2-C6H5;H;H;1:1.6:2;90;69
7;Triphenylphospine;;;1:0.8:1;15;85
8;Hydroquinone;;;1:0.8:1;30;71

a: copper(II) nitrate:hydrogen peroxide [0.46 gram of claycop contains 0.8 mmol of copper(II nitrate].
b: Using 0.8 mmol equivalents of the copper(II) nitrate results in the formation of phenylacetic acid.
[...]

The candle that burns twice as bright burns half as long
 
 
 
 
    Lego
(Stranger)
04-02-03 23:03
No 423400
      Oxidation with Clay/NaClO
(Rated as: excellent)
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Oxidation of alcohols and primary aliphatic amines to
carbonyl compounds using sodium hypochlorite
adsorbed on montmorillonite K10



J. Chem. Research (S), 2000, 224–225


Abstract: NaClO adsorbed on montmorillonite K10 converts alcohols and primary aliphatic amines into corresponding carbonyl compounds.


Solid phase organic synthesis for preparation of various molecules has provide an attractive option for organic synthesis.1–4
Modification of the activity and product selectivity are the characteristics of this method.
Montmorillonite clays have a great impact in organic synthesis and offer a major breakthrough for the fine chemicals manufacturing industry.3,5
The oxidation of primary and secondary alcohols to the corresponding carbonyl compounds is an important reaction in organic synthesis and the newer oxidative protocols are welcome in spite of the availability of several methods to accomplish this objective.6
Sodium hyphochlorite is a readily available and inexpensive oxidant and has been used for the oxidation of a variety of compounds. Unfortunately the traditional NaClO oxidation methods are limited by the very low solubility of NaClO in most organic solvents. In order to overcome this limitation, milder NaClO oxidation methods such as oxidation under phase-transfer catalysis8 have been developed. However, these methods possess disadvantages, e.g., long reaction time, high temperature and the use of expensive polar aprotic solvents.
This communication reports our finding that NaClO  adsorbed on montmorillonite K10 is an effective oxidizing agent for the rapid oxidation of alcohols and primary aliphatic amines to aldehydes and ketones.
Alcohols are rapidly converted into carbonyl compounds at room temperature by stirring with a NaClO / montmorillonite K10 reagent. This reagent is prepared by mixing weighed amounts of 5% aqueous NaClO (commercial home bleach) and K10 clay. The oxidation reactions are carried out simply by adding 1.2 eq. of the NaClO / K10 clay reagent to the stirred solution of an alcohol in dichloromethane. Aliphatic primary alcohols are oxidized to the corresponding aldehydes, and secondary alcohols to the corresponding ketones. The results are summarized in Table 1.
A variety of oxidizing reagents e.g. Na2SO3,9 NaNO2,10 K2FeO4, 11,12 KMnO4,13 and NaClO under phase transfer catalyst8 have been used for the transformation of amines to carbonyl compounds. Most of the reported reagents require vigorous conditions.8 Some of these reagents involved tedious solvent removal9,10, low yields11–13 and a long reaction time8,10.
Our reagent is a cheap alternative for oxidation of  aliphatic as well as benzylic primary amines with total selectivity and good yields to corresponding aldehydes and ketones (Table 2).
In conclusion, mild reaction conditions, high yields, ease of work-up, stability and reusability of support are the most significant aspects of this method.

Experimental: Chemicals were purchased from Merck, Aldrich and Riedel dehaen AG chemical companies and were used without further purification.
All products are known compounds and they were identified by comparison of their 2,4-dinitrophenylhydrazones’ melting points, IR and 1H-NMR, spectra with those reported in the literature. All yields refer to pure isolated products.

Preparation of montmorillonite K10 supported sodium hypochlorite:
This reagent is prepared by co-grinding NaClO (150 ml, 5% commercial home bleach solution, 100 mmol) and  montmorillonite K10 (150 g, surface 200 m2/g, Fluka) in an agate mortar. A white paste is obtained which must be used immediately.

Oxidation of alcohols to aldehydes and ketones: typical procedure:
Cyclohexanone (200 mg, 2mmol), K10 clay supported NaClO (9.00 g, NaClO content; 3 mmol) and dichloromethane (30 ml) were vigorously stirred in a round bottom flask at room temperature for 30 minutes.
The heterogeneous mixture was then filtered through a sintered glass funnel, and the insoluble material was thoroughly washed with hot solvent. Rotary evaporation of the combined filtrate in vacuo followed by passage through a short column filled with silica gel gave 190 mg (97%) of cyclohexanone, bp 154-156 °C, lit 155.6 °C.

Oxidation of primary amines to aldehydes and ketones: typical procedure:
Benzylamine (214 mg, 2mmol), K10 clay supported NaClO (9.00 g, NaClO content; 3 mmol) and dichloromethane (30 ml) were vigorously stirred in a round bottom flask at room temperature for 30 minutes. The solvent was washed with 2N HCl solution to remove any  unreacted amines. After work-up and purification as above, 198 mg (93%) of benzaldehyde was obtained, bp 176–178 °C, lit 179 °C.

Table 1 Oxidation of alcohols to carbonyl compounds by NaClO / K10 clay
Alcohol;Time (min.);Product;Yield (%)
4-hydroxy-3-methoxybenzaldehyde;25;Vanilin;96
2,4,6-trimethylbenzyl alcohol;30;2,4,6-trimethyl benzaldehyde;93
4-chlorobenzyl alcohol;20;4-chlorobenzaldehyde;98
9-fluorenole;35;9-fluorenone;98
4-nitrobenzyl alcohol;20;4-nitrobenzaldehyde;95
Cyclohexanol;30;Cyclohexanone;97
Cinamyl alcohol;25;Cinamaldehyde;89a
Furfuryl alcohol;25;2-furaldehyde;97

a) Yield of 2,4-dinitrophenylhydrazone derivative.


Table 2 Oxidation of primary amines to carbonyl compounds by NaClO / K10 clay
Amine;Product;Time (min);Yield (%)
Ethyl amine;Acetaldehyde;30;85
N-buthyl amine;n-buthylaldehyde;25;88
Benzyl amine;Benzaldehyde;30;93
Isopropyl amine;Acetone;65;82a
Cyclohexyl amine;Cyclohexanone;55;90
2-phenylethyl amine;Phenyl;acetaldehyde;60;89
4-methylbenzyl amine;4-methylbenzaldehyde;35;96a
3-phenylpropyl amine;Dihydrocinnamaldehyde;50;91
3-chlorobenzyl amine;3-chlorobenzaldehyde;45;86
4-chlorobenzyl amine;4-chlorobenzaldehyde;50;90

a) Yield of 2,4-dinitrophenylhydrazone derivative.


References
1 J.H. Clark, S.R. Cullen, S.J. Barlow and T.W. Bastock, J. Chem. Soc., Perkin Trans. 2., 1994, 2, 2013.
2 P. Laszlo, Preparative Chemistry Using Supported Reagents, Academic Press Inc., San Diego, 1987.
3 M. Balogh and P. Laszlo, Organic Chemistry Using Clays., Springer-Verlag, Berlin, 1993.
4 K. Smith, Solid Supports and Catalyst in Organic Synthesis, Ed. Ellis Harwood, Chichester, 1992.
5 O. Sieskind and P. Alberch, Tetrahedron Lett., 1993, 34,  1197.
6 I.E. Marko, P.R. Giles, M.S. Tsukazaki, M. Brown and C.J. Urch, Science., 1996, 274, 2044.
7 M. Hudlicky, Oxidation in organic chemistry, ACS, Washington DC, 1990.
8 G.A. Lee, and H.H. Freedman, Tetrahedron Lett., 1976, 20, 1641.
9 R.G.R. Bacon and D.J. Stewart, J. Chem. Soc., Chem. Commun., 1996, 1384.
10 K.H. Scheit and W. Kampe, Angew. Chem., 1965, 77, 811.
11 Y. Tsudu and S. Nakajima, Chem. Lett., 1978, 1397.
12 R.J. Audette, J. Quail and W. Smith, Tetrahedron Lett., 1971, 279.
13 S.S. Rawalay and H. Shechter, J. Org. Chem., 1967, 32, 3129.
14 The Merck Index, 12th Ed., Merck & Co Inc., Rahway, New Jersey, 1996.




Lego will check the mentioned refs as soon as possible and if they have clandestine potential or anything similiar they will be posted.

The candle that burns twice as bright burns half as long