Carvone Carvotanacetone

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). 

G. Vavon has examined the hydrogenation of carvone, in presenc of platinum black as a catalyst, and shown that it takes place in three entirely distinct phases. Carvone fixes successively three molecules of hydrogen, giving dextro-carvotanacetone, then tetrahydrocarvone, and finally carvomenthol. 

Nevertheless, in the hydrogenation of poly-unsaturated molecules the catalyst effects are more evident in the selectivity patterns, as is shown in Table 2 and 3. The selectivity behavior for the various catalysts, show that Rh/MgO is the most selective for carvotanacetone formation. The addition is mainly limited, in these catalysts, to one hydrogen molecule, although in carvone there are three possible sites at which reduction can occur. 

The following important conclusions emerge from this study (i) precursor effect is exhibited in carvone hydrogenation activity, (ii) the Rh/MgO catalysts results to be more selective towards carvotanacetone formation than... 

A Pseudomonas strain hydroxylates p-menthane to cis-p-menthan-l-ol,84 and microbiological reduction of carvotanacetone with Pseudomonas ovalis gives similar results85 to those obtained with carvone (Vol. 5, p. 24, incorrectly reports inversion at C-4). (—)-Carvotanacetone (30) gives (+)-carvomenthone (31), (—)-... 

The starting material was dihydrocarvone (carvotanacetone (127)), which is easily prepared from carvone (Scheme 12) (772). Thus, this strategy bears the prerequisite for an EPC-synthesis. The key step was the Lewis acid-catalyzed... 

Further n.m.r. data have been published on isomeric menthyl cf. Vol. 7, pp. 5, 29) and carvomenthyl alcohols and some derivatives.N.m.r. data include [Eu(dpm)3] methyl shift assignments in the menthols, the menthones, two carvomenthols, the isopulegols, the carveols, carvone, carvotanacetol, and carvotanacetone, together with the relevant acetates, and an analysis of... 

J.-L. Luche, L. Rodn guez-Hahn, and P. Crabbe, J.C.S. Chem. Comm., 1978,601. The paper refers to carvone (18) reduction but the formulae depicted correspond to carvotanacetone and carvo-tanacetol. For additional complex metal hydride reduction data, see Vol. 1, p. 39, ref. 155. 

The initial selectivity of platinum catalysts in carvone hydrogenation depends on the platinum dispersion. For example carvotanacetone (2-methyl-5-isopropylcyclo 2-ene-l-one) is the major product on catalysts with large platinum particles, whereas carvomenthone (2-methyl-5-isopropylcyclohexanone) is the major product on highly dispersed platinum catalysts. 

Activities per site for the carvone hydrogenation on the various monometallic catalysts are shown in Table 2. It can be observed a particle size effect large particles (Cl) are more active than smaller ones (Al). This particle size effect is also observed in the selectivity pattern. Partial hydrogenation (exo double bond) is the main reaction on large particles, the main product being carvotanacetone. On the other hand, small particles are more selective towards carvomenthone, the two double bonds (exo, endo) are hydrogenated. 

Activities and selectivities of bimetallic catalysts for hydrogenation of carvone are reported in Table 3. The results show a decrease of the specific activity of bimetallic catalysts compared to that of monometallic ones. Gold addition also modifies the selectivity patterns. The partial hydrogenation of the exo double bond is increased on both large and small particles on these catalysts carvotanacetone is the main product. 

Oxygenated p-Menthanes. The conformations of dihydrocarvone (148), the diastereoisomeric pairs of the corresponding 1-hydroxy-compound, and some related substances have been studied by temperature-dependent c.d. The conformations of the various stereoisomers (149) of the reduction products of carvotanacetone epoxide, as well as some of the corresponding alcohols from carvone epoxide (150) have been examined through their Hn.m.r. spectra. ... 

The above procedure (Scheme-94) has been used to selectively reduce (-)-carvone to (+) dihydrocarvone and carvotanacetone in 95% and 83% yields respectively by variation of experimental conditions (Scheme-95). ... 

Carvomenthol, T5 Carvomenthone, T5 Carvone, T5 cw-carvotanacetol, T1 Carvotanacetone, T1 Caryophyllene, T6 tranj-caryophyllenic acid, T6 Cascarillin, T39 Cassaic acid, T39 Cassaine, T39 Cassine, K30 Castoramine, K7 ... 

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