Cineole derivatives

Microwave activation and solvent-free PTC have been shown to be of prime efficiency for the synthesis of new benzylidene cineole derivatives (UV sunscreens) by the Knoevenagel reaction. When performed classically by use of KOH in ethanol at room temperature for 12 h (Eqs. 43 and 44) the yield was 30%. This was improved to 90-94% within 2-6 min under PTC + MW conditions (Tabs 5.17 and 5.18) [27, 28],... 

Cineole derivatives, of interest as potential cosmetic products, were obtained under a green chemistry procedure , i. e. one without solvent, with microwave activation according to Scheme 8.54. 

The PTC process was also used for the synthesis of cineole derivatives already covered in Sect. 8.3.2.8, and more recently in Green Chemistry [87]. 

Cineol forms a number of crystalline derivatives, amongst which may be mentioned the hydrobromide, CjgHjgO. HBr, melting at 56°, and the compound with iodol, CjdHjgO. C I NH, which forms yellowish-green crystals, melting at 112°. It also forms a crystalline compound with resorcinol, which has been used as a basis for its quantitative determination. This compound consists of 2 molecules of cineol with 1 of resorcin, and forms needle-shaped crystals, melting at 80°. 

Traditionally, the majority of the studies in this area have emphasized the analysis of microorganisms, in particular of soil actinomycetes, as the most relevant source of potential herbicide agents. The plant kingdom, however, has also been explored for the discovery of new herbicides. So far, bialaphos, originally isolated from different Streptomyces strains, is the only commercial herbicide derived from a microbial source. On the other hand, cymethylin, an analog of the mono terpenoid 1,8-cineole, as well as... 

According to Ref 2, camphor oil is a col, natural oil with characteristic odor, d 0.870 -1.040, nD 1.465-1.481 at 20° sol in eth, chlf insol in ale its chief constituents are pinene, camphor, cineol, phellandrene, dipentene, safrol eugenol. Derived by distg the wood of the Cinamonum camphora and separating the oil from solid camphor. Used as substitute for turpentine oil in varnishes, cheap soaps, shoe polishes, etc... 

The seed oil in A. subulatum has been the subject of several investigations. Nigam and Purohit (1960) obtained 2.5% oil from the seeds and fractionated the oil into different cineole-rich fractions. Lawrence (1970) separated the components of the oil by preparative gas chromatography, identified them by their IR spectra and retention data and found the major component, 1,8-cineole, in 74%. Patra et al. (1982) studied the oil by packed column GC and reported that its major components were sabinene (9.1%), y-terpinene (16.2%) and 1,8-cineole (63.3%). In another study, Gupta et al. (1984) analysed oils derived from different strains of A. subulatum growing wild in Sikkim and found the 1,8-cineole content varied from 77 to 89%. The oil and volatile concentrate produced by liquid carbon dioxide extraction of A. subulatum were compared by Kaur et al. (1993). 

The rosemary extracts were collected as separate samples succesively in time. Each of them was analysed separatively and the results are listed in Table 4. The concentrations of a-pinene, champhene, p-cimene and limonene decreased with extraction time, while that of the oxygeneted derivatives (cineol, linalool, camphor, bomeol and verbenon) increased significantly. 

Bondavalli et al. have found some stereoselectivity in the reduction of the oxime (180) derived from 1,8-cineol. With lithium aluminium hydride it mostly gives the endo-amine (181), but with sodium in Jcohol the exo-amine predominates. The bromination of pinol (182) —not naturally occurring—has been shown by Wolinsky to occur with rearrangement. Wallach s structure is incorrect the product is 6,7-dibromo-1,8-cineol (183). Treatment of this with hydrogen bromide leads to the ring-opened pinol tribromide (184). de Mayo... 

Terpin. Terpin Hydrate. Cineol.—In addition to these monohydroxy derivatives there is another important one which is a dihydroxy menthane known as terpan-di-ol or terpin. Terpin boils at 258° and readily forms a crystalline hydrate, terpin hydrate, which melts at 117°. It also loses water yielding an anhydride known as cineol. Terpin and terpin hydrate are obtained from the terpenes in oil of turpentine by the action of acids. Cineol is found in eucalyptus oil. The constitution of these compounds is proven by their relation to geraniol (p. 167). When treated with 5 per cent H2SO4 two molecules of water are added to geraniol and terpin hydrate is formed. This by loss of one molecule of water forms a closed ring yielding terpin and this by loss of another molecule of water yields cineol. These relationships are as follows ... 

Cyclic Terpenes.— The cyclic terpenes and their oxidation derivatives such as pinene, limonene, menthol, terpineol, cineol, carvone, fenchone and camphor are found in a large number of essential oils... 

Composition Eugenol (65-85%), methyl eugenol, 1,8-cineole and numerous mono-and sesquiterpene hydrocarbons, e.g. myrcene, p-caryophyllene and humulene [230], The commercially available oils also derive from the leaves and possess a similar composition, whereas the content of methyl eugenol in most cases is higher in the berry oil [231, 232[. For further research results see [233[. 

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