Carvone systems

The activity of the FePeCli6-S/tert-butyl hydroperoxide (TBHP) catalytic system was studied under mild reaction conditions for the synthesis of three a,p-unsaturated ketones 2-cyclohexen-l-one, carvone and veibenone by allylic oxidation of cyclohexene, hmonene, and a-pinene, respectively. Substrate conversions were higher than 80% and ketone yields decreased in the following order cyclohexen-1-one (47%), verbenone (22%), and carvone (12%). The large amount of oxidized sites of monoterpenes, especially limonene, may be the reason for the lower ketone yield obtained with this substrate. Additional tests snggested that molecular oxygen can act as co-oxidant and alcohol oxidation is an intermediate step in ketone formation. 

The mammalian olfactory system possesses enormous discriminatory power. It is claimed that humans can perceive many thousands of different odorous molecules, termed odorants. Even slight alterations in the structure of an odorant can lead to profound changes in perceived odor quality. One commonly cited example is carvone, whose L- and D-stereoisomers are perceived as spearmint and caraway, respectively. However, more subtle molecular alterations can also generate striking changes in perception. 

Literature examples include one-, two-, and three-step hydrogenation reactions, hi each case, the reactant and product concentrations were monitored, as were intermediates or side reaction products as necessary. Simple peak height or area measurements were sufficient to generate reaction profiles for the reduction of cyclohexene [116] and of l-chloro-2-nitrobenzene [117]. However, for more spectrally complex systems, such as the reduction of carvone and of 2-(4-hydroxyphenyl) propionate, multivariate curve resolution (MCR) was required [117]. 

Catalytic Experiments. Activities were performed in a 1 liter Parr reactor. A typical experiment was performed as follows at a temperature of 100 °C, 100 mg of the catalyst and 1.5 /. wt of (-)-carvone (Aldrich) in n-hexane solution (100 ml) were Introduced in a high pressure Parr reactor equipped with mechanical stirring and automatic temperature control. Before introducing the hydrogen the system was purged 2 or 3 times with Nz> The total hydrogen pressure was 21 atm. The reaction products were analysed by gas chromatography. NMR and Mass Spectrometry and identified as unreacted carvone, carvotanacetone, carvomenthone and three carvomenthol stereoisomers (axial-equatorial, equatorial-equatorial and equatorial-axial). 

The electrooxidation of the enol acetate 23 of isopinocamphone generally leads to three different types of products 7-carvone 7, 8-acetoxy-p-menth-6-en-2-one 24, and 2-acetoxy-2,6,6-trimethylbicyclo[3.1.1]heptan-3-one. The product distribution is largely dependent on the combination of solvent and electrolyte. It is found that the enol acetate 23 leads to /-carvone 7 selectively, if electrolysis is performed in a CH2C12/ AcOH(8/l)—Et4NOTs—(C) system (Scheme 3-8)55>. 

Whitten W. M., Williams N. H., Armbruster W. S., Battiste M. A., Strekowski L. and Lindquist N. (1986) Carvone oxide an example of convergent evolution in euglossine-pollinated plants. System. Bot. 11, 222-228. 

Carvone can be oxidized by the MT0/H202 system with the original procedure by Herrmann using tort-butanol as the solvent. After 18 h at 5°C, a conversion of 85% with a selectivity of 98% for the epoxide of the terminal (8,9) double bond is obtained [68]. Using the same procedure, citral is oxidized in a mere 28% yield of the 2,3-epoxide [48]. When using the biphasic system with CH2C12, however, full conversion and selectivity for the epoxide are obtained after 3 h at 0°C. Unfortunately, it was not specified which epoxide is formed. This biphasic system is also very effective for the oxidation of citronellal, giving nearly full conversion and selectivity for the epoxide after 2 h at 4°C [51]. 

Die intramolekulare photochemische C4-Ringbildung zwischen einem a.B-ungesiittigten Keton-System und einer Doppelbindung ist seit langem bekannt (vgl. die Photoisomerisierung des Carvons, Kap. 3.1.). Zahl-... 

Naming Lipid Stereoisomers The two compounds below are stereoisomers of carvone with quite different properties the one on the left smells like spearmint, and that on the right, like caraway. Name the compounds using the RS system. 

Maruoka has successfully developed a highly accelerated Oppenauer oxidation [31,32] system using a bidentate aluminum catalyst [29]. This modified, catalytic system effectively oxidizes a variety of secondary alcohols to the corresponding ketones as shown in Sch. 9. For example, reaction of (2,7-dimethyl-l,8-biphenylene-dioxy)bis(dimethylaluminum) (8, 5 moI%) with carveol (14) at room temperature in the presence of 4-A molecular sieves, and subsequent treatment with pivalaldehyde (3 equiv.) at room temperature for 5 h yielded carvone (15) in 91 % yield. Under these oxidation conditions, cholesterol (16) was converted to 4-cholesten-3-one (17) in 75 % yield (91 % yield with 5 equiv. t-BuCHO). 

Of special interest are the relative rates of reduction of various cyclic enones, such as carvone, acetylcyclohexene and pulegone (Scheme 60). While the enone system in carvone is frozen in its transoid... 

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