A-terpinyl methyl ether

Reactions in the Batch Reactor - Methanol reacts with limonene over acidic catalysts in a batch reactor to l-methyl-4-[a-methoxyisopropyl]-l-cyclohexene (a-terpinyl methyl ether) as the main reaction product (see Figure 8 R = Me). Besides the desired methoxylation, isomerization reactions leading to terpinolene and traces of a- and y-terpinene can be observed. Furthermore, the addition of methanol to the terpinyl methyl ether leads to the undesired cis- or fra/w-1,8-dimethoxy-p-menthane. The amount of unidentified products does not exceed 1%. At high temperatures and long reaction times the reverse reaction of the a-terpinyl methyl ether and the other addition products to limonene and its isomers can be observed. The reaction scheme of the alkoxylation of limonene is illustrated in Figure 10... 

C. The selectivity to the a-terpinyl methyl ether increases within 9h TOS. However, the selectivity is lowered to 75% at 80 °C while at a lower temperature it increases to 95% during 9 h TOS. 

At the limonene conversion of about 60% and a reaction temperature decreased to 40 °C, selectivities higher than 95% are achieved. A temperature lower than 40 °C causes a noticeable decrease of the limonene conversion. In spite of this, selectivity to a-terpinyl methyl ether remains on the same level of about 95%. The product distribution is nearly the same as in the batch reactor. 

The selectivity to the a-terpinyl methyl ether increases with the reduction of the residence time. The experiments have revealed that not only higher reaction temperature and the limonene conversion above 90%, but also a longer contact time caused by a lower WHSV favor the consecutive reaction of the excess methanol with l-methyl-4-[a-methoxyisopropyl]-l-cyclohexene to cis- or trans-1,8-dimethoxy-p-menthane. 

Reactions in the Batch Reactor - The addition of methanol to a-pinene in the presence of the above mentioned P-zeolite as catalyst in the batch reactor results in the cleavage of the cyclobutane ring and yields 1-methyl-4-a-methoxyisopropyl]-1-cyclohexene (a-terpinyl methyl ether) as the main reaction product. The most common by-products to be found are isomerization compounds like camphene, limonene and terpinolene, and several bicyclic and double addition products, e.g. endo- or exo-methyl bornyl ether, endo- or exo-methyl fenchyl ether and cis- or trans-1,8-dimethoxy-/)-menthane. 

Methoxylation of a-pinene in the continuous flow-type apparatus with an integral fixed bed reactor over P-zeolite as catalyst shows very similar results as in the batch reactor. The dependence of a-pinene conversion and selectivity to the a-terpinyl methyl ether on temperature and time on stream are in agreement with observations for limonene methoxylation. 

For mixtures of methanol and a-pinene, the highest yield of corresponding a-terpinyl methyl ether is only of about 50% (conversion 99%, selectivity 51%) in both reactor types, as several bicyclic and double addition products are formed in parallel. The selectivity of all addition products can reach values of about 85%. 

Another patent (U.S. Patent 4,735,803) claims the same using lemon oil and a-terpinyl methyl ether. 

Another similar formulation (United States Patent 4847292) claims that a mixture of citronellyl nitrile, citronellol, a-terpinyl methyl ether, and lemon oil repels dogs. 

This terpine ether known as terpinyl methyl ether is a light, colored liquid with a pleasant odor, which contains some impurities. It is a strong solvent for resins and is used in alkyd enamels to the extent of 2 per cent to which it imparts flow. 

When geraniol reacts with phenols in the presence of acid, the common products are usually cyclized the use of 1 % oxalic acid has now been found to minimize cyclization in the reaction between orcinol and geraniol. Nerol has been labelled with deuterium in various positions [a, b, c, and d in (32)] and then converted into the chloride (33). Kinetic isotope effects on hydrolysis of (33) were measured, and 7r-participation in the cationic intermediate (34) leading to the cyclized terpinyl derivatives is discussed. Schwartz and Dunn proposed to use the complex (35), from geranyl methyl ether, as a model for a farnesol cyclization. They were not able to isolate this complex (although there was some evidence for its formation), the main complex (36%) being a dimeric a-complex (36), together with 39 % of the ketone (37), but no cyclized material. The cyclization of the acid chloride (38) to menthone and the C9 hydrocarbon (39) with tributyltin hydride, and also the optimum conditions for the cyclization of (-i-)-citronellal... 

The essential oil contains mainly pinocam-phone, isopinocamphone, a- and P-pinenes, camphene, and a-terpinene, which together constitute about 70% of the oil. Other constituents present include pinocampheol, cineole, linalool, terpineol, terpinyl acetate, bomyl acetate, cw-pinic acid, cw-pinonic acid, myrtenic acid, myrtenol methyl ether, (i-2-hyckoxy-isopinocamphone, methyl myr-tenate, cadinene, and other unidentified compounds totaling more than 50 (karrer list... 

The hydroformylation of allyl ethers with cumenyl, isobornyl, 2-methyl-2-pentanol, and terpinyl groups was patented by IFF (Table 6.4) [186]. In all cases, the linear and branched aldehydes were formed. After distillation, the odors of the linear compounds were evaluated. The isobornyl-derived aldehyde was reduced to give a corresponding hydroxy butylether with a typical patchouli aroma. 

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