A-Isophorone

Isophorone usually contains 2—5% of the isomer P-isophorone [471-01-2] (3,5,5-trimethyl-3-cyclohexen-l-one). The term a-isophorone is sometimes used ia referring to the a,P-unsaturated ketone, whereas P-isophorone connotes the unconjugated derivative. P-lsophorone (bp 186°C) is lower boiling than isophorone and can be converted to isophorone by distilling at reduced pressure ia the presence of -toluenesulfonic acid (188). Isophorone can be converted to P-isophorone by treatment with adipic acid (189) or H on(Ill) acetylacetoate (190). P-lsophorone can also be prepared from 4-bromoisophorone by reduction with chromous acetate (191). P-lsophorone can be used as an iatermediate ia the synthesis of carotenoids (192). 

Cyclohexanecarbonyl chloride EK Triethylamine MCB, EK N-Methyl-A -nitroso-p-toluenesulfonamide A Isophorone MCB, A d < -Octalone-2 (Chapter 9, Section III)... 

Figure 2. Comparison of initial rates and selectivities (related to olefin and peroxide) for the epoxidation of a-isophorone with t-butyl hydrojjeroxide at 60 C over (a) low-temperature aerogel (LT) (20 wt% Ti02), (b) titania-on-silica, (c) TS-1 and (d) xerogel.

Isomerization of jS-isophorone to a-isophorone has been represented as a model reaction for the characterization of solid bases 106,107). The reaction involves the loss of a hydrogen atom from the position a to the carbonyl group, giving an allylic carbanion stabilized by conjugation, which can isomerize to a species corresponding to the carbanion of a-isophorone (Scheme 9). In this reaction, zero-order kinetics has been observed at 308 K for many bases, and consequently the initial rate of the reaction is equal to the rate constant. The rate of isomerization has been used to measure the total number of active sites on a series of solid bases. Figueras et al. (106,107) showed that the number of basic sites determined by CO2 adsorption on various calcined double-layered hydroxides was proportional to the rate constants for S-isophorone isomerization (Fig. 3), confirming that the reaction can be used as a useful tool for the determination of acid-base characteristics of oxide catalysts. 

A. Isophorone (18), and Mesityl Oxide (18) are not compatible with Group 8, Alkanolamines. 

Oxidation of a-isophorone (3) with /-butyl hydroperoxide catalyzed by PdfOAc), and N(C2Hj), results in 4 as the only oxidation product. 

The total neutral essential oil from M. oleifera leaves is composed of 44 constituents and include toluene, 5-ter/-butyl-l,3-cyclopentadiene, benzaldehyde, 5-methyl-2-furaldehyde, benzeneacetaldehyde, linaloloxide, 2-ethyl-3,6-dimethylpyrazine, undecane, a-isophorone, benzylnitrile, 2,6,6-trimethyl-2-cyclohexane-l, 4-dione, 2,2,4-trimethyl-pentadiol, 2,3 -epoxycarane, p-menth-1 -en-8-ol, 2,6,6-trimethylcyclohexa-1,3 -dienecarbaldehyde, indole, tridecane, a-ionone, l,l,6-trimethyl-l,2-dihydronaphthalene, a-ionene, (1-damascenone, 3-ionone, ledene oxide, 2-ter/-butyl-l,4-dimethoxybenzene, ( )-6,10-dimethylundeca-5,9-dien-2-one, 4,6-dimethyl-dodecane, 3,3,5,6-... 

The term a-isophorone is sometimes used in referring to the a,jS-unsaturated ketone, whereas j6-isophorone connotes the unconjugated derivatives [1,2]. Isophorone is produced by aldol condensation (trimerization) of acetone under alkaline conditions. Severe reaction conditions effect the condensation and partial dehydration of three molecules of acetone. Both liquid and vapor phase continuous technologies are practiced... 

The oxidation reactions were performed in a closed, mechanically stirred 100 ml glass batch reactor under Ar. For the epoxidation of a-isophorone, 0.2 g catalyst, 9 ml solvent, 7.2 mmol cumene (internal standard) and 77 mmol olefin were introduced into the reactor. The slurry was heated to the reaction temperature and the reaction stauted by adding 13.4 mmol t-butyl hydroperoxide (TBHP, ca. 3 M in isooctane) from a dropping funnel to the vigorously stirred slurry (n = 1000 min ). For the epoxidation of P-isophorone, 20 ml ethylbenzene solvent, 61 mmol P-isophorone, 7.2 mmol cumene and 5.6 mmol TBHP or ciunene hydroperoxide (CHP) were introduced into the reactor in this order. The solution was heated to 80 °C and... 

Several solvents have been tested in the epoxidation of a- isophorone with t-butyl hydroperoxide (TBHP). The best performance of the aerogel was observed in low polarity solvents such as ethylbenzene or cumene (Table 1). In these solvents 99 % selectivity related to the olefin converted was obtained at 50 % peroxide conversion, independent of the temperature. Rasing temperature resulted in increasing initial rate and decreasing selectivity related to the peroxide. The low peroxide efficiency is explained by the homol5d ic peroxide decomposition. Protic polar solvents were detrimental to the reaction due to their strong coordination to the active sites. There was no epoxide formation in water. 

Influence of solvents and reaction temperature on initial rates and selectivities in the epoxidation of a- isophorone catalyst 20 wt% titania - 80 wt% silica, oxidant TBHP... 

Comparison of various heterogeneous catalysts in the epoxidation of a- isophorone... 

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... 

Preliminary experiments revealed that the selectivity of titania-silica aerogel in the epoxidation of P-isophorone was moderate. The selectivity related to the olefin converted was below 90 % at low temperature, and dropped rapidly at 80 °C or above. The most important side reactions were the formation of 3,5,5-trimethyl-2-cyclohexene-4-hydroxy-l-one (2) by ring opening of the epoxide (1), and the isomerization of P- to a-isophorone (3), as shown in Scheme 2. Epoxidation of 2 and 3, and the oxidation at the OH group of 2 to a dicarbonyl compound were slow and the amounts of these by-products were usually aroimd 1 % or less. 

The importance of the acid-catalyzed side reactions are illustrated in Table 3 by the product distribution obtained using either TBHP or cumene hydroperoxide (CHP) as oxidant. The epoxidation with TBHP is faster and considerably more selective. When using CHP, about 20 mol% of the coproduct 2-phenyl-2-propanol was dehydrated to a-methylstyrene. It is likely that the simultaneously formed water increases the (Brpnsted) acidity of the aerogel and thus accelerates the ring opening and - to a smaller extent - the isomerization reactions. No oxidation products were formed in the absence of peroxide, as expected. Slow isomerization from p- to a-isophorone catalyzed by titania-silica was the only reaction observed. The data in Table 3 indicate that the simultaneous presence of peroxide and catalyst in the reaction mixture markedly accelerates the acid-catalyzed isomerization reaction. 

The electron deficiency of a-isophorone seems to affect mainly the reaction rate, whereas the selectivity to epoxide is high (up to 99 %). A comparative study shows that the productivity (peroxide produced per unit time and unit amount of catalyst) of titania-silica is outstanding compared to other types of solid epoxidation catalysts. 

Figure 3.39 Alicyclic isocyanates, (a) Isophorone diisocyanate (or 3-isocyanato-methyl-3,5,5—trimethylcyclohexyl isocyanate), Huels IPDI (b) l,4-bis(isocyanatometh-yl)cyclohexane, Mobay s p-Desmodur (c) l,3-bis(isocyanatomethyl)cyclohexane, Takeda s Hr,XDI (S3.50) (d) Methylene bis(4—cyclohexylisocyanate), Mobay s Desmodur W ( 3.00). also known as H12MDI, RMDI (reduced MD1), and PACM [bis-/ -aminocyclohcxyl methane].

Isophorone [14.268], [14.269] is an unsaturated cyclic ketone. It consists of a-isophorone [78-59-1] (3,5,5-trimethyl-2-cyclohexen-l-one), which contains about 1-3% of the isomer P-isophorone [471-01-2] (3,5,5-trimethyl-3-cyclohexen-l-one). Isophorone is a stable, water-white liquid with a mild odor that is miscible in all proportions with organic solvents. It dissolves many natural and synthetic resins and polymers, such as poly(vinyl chloride) and vinyl chloride copolymers, poly(vinyI acetate), polyacrylates, polymethacrylates, polystyrene, chlorinated rubber, alkyd resins, saturated and unsaturated polyesters, epoxy resins, cellulose nitrate, cellulose ethers and esters, damar resin (dewaxed), kauri, waxes, fats, oils, phenol-, melamine-, and urea-formaldehyde resins, as well as plant protection agents. However, isophorone does not dissolve polyethylene, polypropylene, polyamides. 

A new strategy for the synthesis of xanthophylls was developed in the 1970s by Roche [77]. The cyclic moieties are all derived from the common precursor 6-oxoisophorone (68), which is obtained from inexpensive a-isophorone (69) in two steps. In the liquid phase in the presence of weak acids, or in the gas phase on nickel oxide catalysts [78,79], 69 is in equilibrium with p-isophorone (70), which may be separated from the higher-boiling starting material by fractional distillation (Scheme 21). 

Other bisphenols are often used in place of bisphenol A. Isophorone bisphenol is common and its structure is shown in Figure 4.4. Copolymer PCs are also common where blends of different bisphenols are used. These are often block copolymers. The Tg of the co-PCs can be adjusted by changing bisphenol monomers and their ratios. 

The results showed that the catalyst derived from MgAl-COs-HT is the most active and very selective. Di Cosimo et al. (533,534) have also used MgAl-LDOs to synthesize a,p-unsaturated ketones, and Kelkar et al. (535a) have investigated the optimum conditions for a-isophorone production. In addition, Climent et al. found that activated LDHs show higher activity and selectivity than aluminophos-... 

Under these conditions, no isomerization into the thermodynamically more stable a-isophorone was observed. Remarkably, when the latter was subjected to the same reaction conditions, only hydrogenation took place, showing the general reactivity problems of enone hydroformylation [152]. Since the application of lower syngas pressure (100-150 bar) in the hydroformylation of P-isophorone also mainly yielded the hydrogenation product, the carbonyl group was protected as acetal (Route II) [152]. Surprisingly, under hydroformylation conditions (90 bar, 100 C), the exocyclic aldehyde was formed as the major product, obviously due to a prior Rh-mediated isomerization process. 

Ketoisophorone (KIP) is a key intermediate in the production of nutritional products (e.g. vitamins and carotenoids) and in the flavours and fragrances industries. One option for a technical access to KIP is the catal5rtic oxidation of isophorone (Fig. 16.13). For good selectivity and yield in the oxidation step a thermal isomerisation of a-isophorone to /1-isophorone is necessary. However, in order to avoid this additional step and because the isomerisation equilibrium is strongly in favour of the a-isomer, a direct oxidation of a-isophorone to KIP would clearly be preferred. 

Researchers from BASF developed the Mn(II)-salen- or [Mn(ni)-salen]X-catalysed oxidation of y6-isophorone using salen derivatives with electron-withdrawing substituents without or in the presence of acetates as additives. The increase of ignition temperature of the hase/solvent mixture (ignition point of triethylamine/cUglyme 0°C) and thus a reduction of the explosion risk, was successfully achieved using tripropylamine in dimethylformamide (DMF) or dimethyl acetamide (DMA). With a chloro-substituted [Mn(in)-salen]Cl catalyst in the presence of Uthium acetate and tripropylamine in DMA, KIP was obtained in an 89.4% yield with minor amounts of by-products (1.5% a-isophorone, 1.3% hydroxy-isophorone) (Fig. 16.14). 

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