Isophorone oxidation

Epoxyeyclohexanone has been prepared in 30% yield4 by epoxi-dation of 2-cyclohexen-l-one with alkaline hydrogen peroxide, using a procedure described for isophorone oxide (4,4,6-trimethyl-7-oxabicyclo[4.1.0]heptan-2-one).5 A better yield (66%) was obtained using f r/-butyl hydroperoxide (1,1-dimethylethylhydroperoxide) and Triton B in benzene solution.6 The procedure described here is simple and rapid. 

Isomerized wood rosin, 32, 2 Isonicotinic acid, 37, 7 2-Isonitrosocyclohexanone, 32, 38 Isophorone, 37, 58 ISOPHORONE OXIDE, 37, 58 Isopropyl alcohol, 31, 112 Isopropyl iodide, 30, 34 31, 33 -Isopropylphenylacetamide, 32, 94 Ji-Isopropylphenyldichlorophosphine, 31,89 ISOTHIOCYANIC ACID, 1 -NAPHTHYL ESTER,... 

If the temperature of the reaction mixture is allowed to rise above 30°, the yield of isophorone oxide is diminished. 

If desired, the course of the reaction may be followed by means of the optical density of the reaction mixture at 235 m/. The ultraviolet spectrum of isophorone has a maximum at 235 mp (e 13,300) the ultraviolet spectrum of isophorone oxide has a maximum at 292 mju (e 43). A total reaction time of 4 hours under the conditions specified was found to be ample for the complete conversion of isophorone to its oxide. If the conversion is not complete, the product cannot be separated from the unchanged isophorone without recourse to precise fractional distillation. The absence of isophorone from the final product may be verified by examination of the spectrum at 235 mp. 

Isophorone oxide has been prepared by the epoxidation of isophorone with alkaline hydrogen peroxide.2 3... 

Reduction of a, ji-epoxy ketones with NaHTe (typical procedure) ji-Epoxy ketonesP To a solution of NaHTe (prepared from Te (1.30 g, 10 mmol) and NaBH (0.90 g, 0.24 mmol)) in EtOH is added isophorone oxide (0.616 g, 4 mmol) in EtOH (4 mL). An instantaneous... 

Noteworthy features of these reactions are the high predominance of E stereochemistry in the case of aldehydes and the good results obtained even with highly enolizable ketones (such as cyclopentanone), a, -epoxy ketones (isophorone oxide) and a,j8-unsaturated compounds (benzalacetophenone and cinnamaldehyde). 

The preparation of isophorone oxide was described in an earlier volume of this series.5... 

The 4a,5a-oxido isomers of Formulas 302 and 303 give the same products (Formulas 304 and 305) (122). Irradiation of mesityl oxide epoxide 306 gives 3-methyl-2,4-pentanedione (Formula 307) in low yield (123). Similar irradiation of isophorone oxide (Formula 308) gives both Formulas 309 and 310 (123). 

Terpene epoxides are very reactive compounds. Some products formed by isomerization of such epoxides are valuable raw materials for perfumes, synthetic flavourings and pharmaceuticals, and also provide useful intermediates in organic syntheses. The isomerization of isophorone oxide 23 (Eq. 15.2.9) was originally investigated by H.O. House and R.L. Wasson using boron trifluoride etherate as a homogeneous catalyst (24). 

Table 15.2 Conversion and selectivities obtained with used zeolites in the liquid phase isomerization of isophorone oxide 23...

The blank test in liquid phase yields less than 1% conversion. Unlike non-zeolitic catalysts, except for H-Nafion, most zeolites yield complete conversion. A high yield of the keto aldehyde 24 up to 81%, was surprisingly attained by using H-FER as a heterogeneous catalyst. For the rearrangement of isophorone oxide, the presence of acidic sites is necessary for the catalytic activity. The reactivity of H-FER can be explained by the acidic outer surface of the catalyst Molecular modeling showed that the isophorone epoxide is too bulky for the small pore size of ferrierite. 

The data were correlated to that obtained by Sheldon et al.(30) in the isophorone oxide rearrangement. There, a dealuminated mordenite was used and a... 

TOS = 4h T = 250°C solvent toluene toluene/isophorone oxide 2 1 wt/wt nitrogen flow 8 1 h 1 WHSV = lh l atm. pressure the numbers in parentheses correspond to the SiCVAhOj or SiCVEhCb ratios... 

In conclusion, the use of zeolites as catalysts in the isomerization of isophorone oxide 23, yields up to 86% keto aldehyde 24. The formation of 26 by... 

Isumerizutiun of isophorone oxide" to a rearranged aldehyde is accomplished similarly except that the reaction mixture is let stand for 30 min. before quenching. 

The preformed anion from (112) was treated with ethyl pyruvate to give (113) as a mixture of isomers. Isophorone oxide reacts with the anion generated from (114) to yield an epoxy-ester as a mixture of isomers. ... 

Further reactions on these compounds lead to other oxidised products in which the lack of stereochemical control in the epoxidation is unimportant, so, for example isophorone oxide rearranges with various catalysts to the cyclopentanone 182 (80% yield) while both isomers of pulegone oxide 179 gives the cycloheptadione29 183 (78% yield). Exhaustive methylation of the extended enolate produced by reduction of 181 gives 184 in good yield.28... 

It is also interesting to compare various types of solid catalysts in the epoxidation of a-isophorone. Unfortunately, a real comparison is rather difficult, as the reaction conditions (temperature, oxidant, concentrations) are different for each catalyst. Due to the lack of information, the comparison shown in Table 2 is based only on the productivity, i.e. the amount of isophorone oxide produced in unit time using unit amount of catalyst. Two set of data were chosen for the 20 wt% titania - 80 wt% silica aerogel, and the best published data were chosen for the hydrotalcite [16, 17] and the alumina-supported KF [17, 18]. We assumed that the... 

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