Wet alumina

Cl2, ammonium nitrate on Clayfen, Oxone on wet alumina, silver nitrate and iodine,2,3-dichloro-5,6-dicyano -1,4-benzoquinone (DDQ) in acetonitrile... 

The regeneration of carbonyl compounds from 1,3-dithianes can be achieved using potassium hydrogen persulfate, Oxone , supported on wet alumina <96SL767> and by periodic acid under non-aqueous conditions <96TL4331>. The deprotection of benzyl substituted 1,3-dithianes can be achieved using the one electron oxidant [Fe(phen)3](PF6)3 <96SL315>. 

FIGURE 26.35 Master curve of the side force coefficient of two tread compounds with different glass transition temperatures on wet Alumina 180 A 3,4 IR Tg = —21°C and OESBR Tg = —46°C. Two spot measurements at two different water temperatures show that the ranking if the two compounds reverses. (From Grosch, K.A., Kautschuk, Gummi, Kunststojfe, 6 m, 432, 1996.)... 

FIGURE 26.38 Correlation and regression coefficients between road test ratings obtained on three different wet road test tracks and laboratory ratings obtained on a wet Alumina 60 laboratory surface as function of... 

Figure 26.42 compares the correlation coefficient between a road test on wet concrete and the laboratory side force measurements of the six compounds of Table 26.2 on blunt, wet Alumina 180 (a) with a log oxv-log v evaluation and (b) with a temperature-log v evaluation. It appears that the... 

Symmetrical and unsymmetrical benzoins have been rapidly oxidized to benzils in high yields using solid reagent systems, copper(II) sulfate-alumina [105] or Oxone-wet alumina [105, 106] under the influence of microwaves (Scheme 6.32). Conventionally, the oxidative transformation of a-hydroxy ketones to 1,2-diketones is accomplished by reagents such as nitric acid, Fehling s solution, thallium(III) nitrate (TTN), ytterbium(III) nitrate, ammonium chlorochromate-alumina and dayfen. In addition to the extended reaction time, most of these processes suffer from drawbacks such as the use of corrosive acids and toxic metals that generate undesirable waste products. 

Oxone has been successfully used in aprotic solvents for oxidation reactions by dispersing it on an alumina surface. Thus, the oxidation of secondary aliphatic, alicyclic and benzylic alcohols using Oxone/wet alumina oxide in CH2CI2 or CH3CN afforded ketones in good to excellent yields (70-96%). Similarly, the conversion of cycloalkanones to lactones is also reported. 

Keywords silyl ether, tetrahydropyranyl ether, deprotection, wet alumina, chromium oxide, ketone, aldehyde... 

The compound 3 can be easily prepared, in one pot, through a solvent-free procedure by nitroaldol reaction of nitroalkane 1 (2.2 mmol) and aldehyde 2 (2.2 mmol, freshly distilled), on activated neutral alumina (0.6 g, the alumina was added to a mechanically stirred solution of 1 and 2, at 0°C, then at room temperature for 20 h). Then, in situ addition (0°C) of wet-alumina supported chro-mium(VI) oxide (0.88 g (8.8 mmol) of C1O3 and 2.64 g of wet alumina). After standing for additional 20 h, the product was extracted with diethyl ether and passed through a bed of alumina. Evaporation of the organic solvent and flash chromatographic purification afforded the pure a-nitro ketone 3 in good yields (68-86%). 

For the intermolecular version, strained alkenes such as norbomene give satisfactory results. Cyclopentenones are obtained in good yields by the reaction of alkyne Co complex with alkene in the presence of silica. Wet alumina also gives good... 

Oxidation ofaUeyelie ketones to lactones.3 Cycloalkanones in CH2CI2 are oxidized to lactones by Oxone (1) mixed with slightly wet alumina as a heterogeneous mixture. Efficient stirring is necessary to obtain reproducible results. Yields are about 80% for 5- and 6-membered ketones, but are low with higher-membered ketones. 

A number of other inorganic oxidizing agents has also been reported for sulfide oxidation which include [Ru(bpy)2(0)PR3][C104],419 Zn(Bi03)2/ AcOH420 and potassium monopersulfate on wet alumina.421... 

Balzer, B., Hruschka, M., and Gauckler, L., Coagulation kinetics and mechanical behavior of wet alumina green bodies produced via DCC, J. Colloid Interface ScL, 216, 379, 1999. 

The addition of iodine azide to double bonds gives p-iodo azides. The reagent can be prepared in situ from KI—NaNa in the presence of Oxone -wet alumina. The addition is stereospecific and anti, suggesting that the mechanism involves a cyclic iodonium ion intermediate. The reaction has been performed on many double-bond compounds, including allenes and a,p-unsaturated ketones. Similar reactions can be performed with BrNa and CfNa. 1,4-Addition has been found with acyclic conjugated dienes. In the case of BrNa, both electrophilic and free-radical mechanisms are important, whUe with CIN3 the addi-... 

Sharghi, H. Sarvari, M.H. Tetrahedron 2002, 58, 10323. With wet alumina followed by MeS02Cl the product is an amide. 

Condensations. Alumina promotes the formation of a-hydroxyphosphonate esters from aromatic aldehydes and dialkyl phosphonates, and the adducts are converted to a-aminophosphonate esters on reaction with ammonia. A solvent-free synthesis of a-nitro ketones comprises mixing nitroalkanes, aldehydes, and neutral alumina and oxidizing the adducts with wet, alumina-supported CrOj (15 examples, 68-86%). The Knoevenagel reaction, the Michael addition of nitromethane to gcm-diactivated alkenes, and the formation of iminothiazolines from thioureas and a-halo ketones are readily effected with alumina under microwave irradiation. 

Wet alumina-supported chromium(VI) oxide, CH2CI2, 10-25 min, 83-93% yield. " ... 

Oxone, wet alumina, CHCI3, reflux, 15-180min, 70-96% yield. ... 

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