Carvone 1,2-addition

HSCH2CH2SH, Zn(OTf)2 or Mg(OTf)2, CICH2CH2CI, heat, 16 h, 85-99% yield.o ,l3-Unsaturated ketones such as carvone are not cleanly converted to ketals because of Michael addition of the thiol. ... 

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. 

Where multiple products are possible, the CMR and MBR have been employed to optimize conditions for formation of specific components of a reaction sequence. Examples discussed below, were obtained by heating organic substrates such as allyl phenyl ether [46] and carvone [47] in water. Rearrangements, addition or elimination of water and isomerizations occurred, with each transformation favored under tightly defined conditions. 

Acylation of limonene at the disubstituted double bond is favoured by a factor of 2.3 over reaction at the trisubstituted double bond using acetyl hexachloroan-timonate. Mixed alkylcuprate alkylation of tricarbonylcyclohexadienyliron salts has been used to synthesize the a-phellandrene tricarbonyliron complex. Dichlorocarbene addition to limonene in the presence of 1,4-diazabicy-clo[2,2,2]octane is almost 100% stereoselective at the trisubstituted double bond (no yield given) (cf. Vol. 6, p. 31) in contrast to dibromocarbene addition to carvone (Vol. 7, p. 34), dichlorocarbene addition to the carveols is not regio-specific. ... 

Carvone is a chemical component of the spearmint plant that has been shown to enhance the growth and ability of Arthrobacter bacteria to degrade polychlorinated biphenyl (PCB). Until this discovery the only known method of strmnlating the bioremediation of PCBs was addition of biphenyl to the soil however, biphenyl is itself a toxic snbstance. 

The preferred industrial method of carvone synthesis utilizes the selective addition of nitrosyl chloride to the endocyclic double bond of limonene. If a lower aliphatic alcohol is used as solvent, limonene nitrosochloride is obtained in high yield. It is converted into carvone oxime by elimination of hydrogen chloride in the presence of a weak base. Acid hydrolysis in the presence of a hydroxylamine acceptor, such as acetone, yields carvone [88]. 

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. 

Michael addition of cyanide to both (+)- and (-)-carvone 1 has been studied in detail. All four possible products 2 can be obtained depending on the conditions, and it has been shown that 2 (P-CN, p-Me) is the kinetically controlled product, as first described by Lapworth in 1906. Reaction of 2 with pentyl nitrite in the presence of NaOEt/EtOH is strongly exothermic, and the temperature of the reaction mixture must be kept below 0°C. The product, formed in 62% yield, is the isoxazoloazepine 3. 

A new study has revealed that allylmagnesium, allylindium, and allylbismuth generally exhibit a preference for axial addition to cyclohexenones (in the 1,2-addition). Allylmagnesium was found to be the most stereoselective reagent. Reactions with carvone (an a-methylated enone) were most selective, except that allylbismuth was inert to this substrate.225... 

Ionene, a commercial fragrance, has been prepared traditionally by treatment of a- and /3-iononcs with hydriodic acid containing phosphorus or by distillative heating in the presence of 0.5% iodine. In an unoptimized demonstration, cyclization occurred more cleanly and simply by MBR with /3-ionone in water at 250 °C (Scheme 19) [83]. Work-up also was facilitated, as the need for removal of catalyst or the formation and separation of bi-products was avoided. At elevated temperature, the addition of water to olefins can occur readily, without adding catalyst. (S)-(+)-carvone in water for 10 min at 180 °C afforded optically pure 8-hydroxy-p-6-mcnlhcn-2-one as an intermediate toward carvacrol [84], Addition of water across the 8,9-double bond of carvone occurred regioselectively, by Markovnikov addition. Carvacrol itself was obtained almost quantitatively from carvone at 250 °C after 10 min (Scheme 19) [84]. 

The studies that eventually led to the synthesis of 6 started by installation of one of the all-carbon stereocenters by addition of vinylmagne-sium bromide to the lithium enolate of (i )-carvone oxide 120. This reaction afforded compound 121 as a single isomer, albeit in only 30% isolated... 

Many other ketones and aldehydes are used as flavorings and additives to foods, drugs, and other products. For example, benzaldehyde is the primary component of almond extract, and (- )-carvone gives spearmint chewing gum its minty flavor. Table 18-4 lists some simple ketones and aldehydes with well-known odors and flavors. Pyrethrin, isolated frompyrethrum flowers, is commercially extracted for use as a natural insecticide. Natural or not, pyrethrin can cause severe allergic reactions, nausea, vomiting, and other toxic effects in animals. 

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