Geranylacetone

Geranyl acetoacetate (685) is converted into geranylacetone (686). On the other hand, a mixture of E- and Z-isomers of 688 is obtained from neryl acetoacetate (687). The decarboxylation and allylation of the allyl malonate or cyanoacetate 689 affords the o-allylated acetate or nitriie[447]. The trifluoromethyl ketone 691 is prepared from cinnamyl 4.4,4-trifluoroacetoace-tate (690)[448],... 

The same complex functions as the catalyst in the Rhone-Poulenc process (Mercier and Chabardes, 1994) for the manufacture of the vitamin A intermediate geranylacetone, via reaction of myrcene with methylacetoacetate in a biphasic system (Fig. 2.28). 

Juttner, F. (1979). Algal excretion product, geranylacetone-potent inhibitor of carotene biosynthesis in syn-echococcus. Zeitschrift Naturforschung C 34(11) 957-960. 

Simkin, A. J., S. H. Schwartz et al. (2004a). The tomato carotenoid cleavage dioxygenase 1 genes contribute to the formation of the flavor volatiles beta-ionone, pseudoionone, and geranylacetone. Plant J. 40(6) 882-892. 

The ruthenium complex of 49 was chosen due to its easy accessibility and because preliminary experiments had shown that simple non-prochiral aliphatic ketones such as 4-methyl-cyclohexanone are quantitatively reduced. This positive outcome encouraged us to test various prochiral aliphatic ketones 64-75. The results using standard conditions are summarized in Fig. 23. Most substrates could be reduced in good yields and the enantioselectivities of six alcoholic products are higher than 85%, 2-decanone 67 and geranylacetone 68 showed even ee s of 95%, demonstrating that the concept works well not only for aromatic ketones. 

To support the proposed hydride transfer as shown for the substrate geranylacetone 68 in Fig. 30 proline was linked to the primary face of P-CD yielding the tertiary amine 101 which was complexed with ruthenium and employed to ATH under standard conditions. No product was formed at all which is in good agreement with observations by other groups (31,49,50). The presence of a hydrogen... 

Geranylacetone is an intermediate in the synthesis of other fragrance substances. It is used in perfumery in rose compositions, for example, in soap perfumes. 

Addition of Active C-H Compounds to Dienes the Rhone-Poulenc Process for Geranylacetone - Geranylacetone is a precursor of isophytol, a key intermediate in the manufacture of vitamine E (tocopherol) (see Figure 16), the world market of which is 10 000 t/a at a price of 25-30 /kg tocopherylacetate.54... 

Figure 17 The novel biphasic Rhltppts-calalysed Rhone-Poulenc process for the manufacture of geranylacetone.

Rhone-Poulenc uses carbon-carbon coupling for an efficient route to geranylacetone with a water-soluble Rh/tppts catalyst (141). The addition of myrcene to acetylacetic add methyl ester is regioselective (>99%) [Eq. (15)]. 

Numerous dienes can be used as reactants, e.g., isoprene, myrcene, and famesene, and several compounds can be used as active methylene compounds. The reaction proceeds in an aqueous liquid-liquid system, with the conversion regulated by the time of contact between the phases, which is controlled by the stirring. The organic products are easily separated by simple decantation, and the aqueous phase containing the catalyst can be recycled. This reaction was industrialized to produce intermediates for vitamin E such as geranylacetone. The capadty is about 1000 tons/year. 

As in the discussion of the acyclic monoterpene ketones (see 1.1.3) instead of the sesquiterpene ketones, the structurally related compounds neryl-(176) and geranylacetone (169) will be reviewed. Indeed, as mentioned before, neryl- and geranylacetone are the norsesquiterpene -analogues of 6-methyl-5-hepten-2-one, which is the /1-oxidation product of nerol and geraniol, just like neryl- and geranylacetone are the bioconversion products of famesol (see 2.1.1). 

As mentioned before (2.1.1) Arfmann et al. [133] studied the co-hydroxylation of the sesquiterpenes nerolidol and famesol and the related compounds neryl- and geranylacetone. This was done because co-hydroxylated sesquiterpenes are important intermediates in the synthesis of industrially used fragrances and flavours. Aspergillus niger ATCC 9142 and Rhodococcus rubropertinctus DSM 43197 were unable to hydroxylate nerylacetone or its -isomer geranylacetone, at the co-position of the molecule. Incubation of nerylacetone with Mucor circinelloides CBS 27749 for 25 hr resulted in seven transformation products, including one co-hydroxylation compound, in 3% yield [140]. 

The bioconversion of geranylacetone with Aspergillus niger yielded the co-hydroxylation product 11-hydroxygeranylacetone and the vicinal diol (S)-(-)-9,10-dihydroxygeranylacetone as in the case of nerolidol and famesol [135]. The same reactions were noticed in the bioconversion of geranylacetol. 

Fig. (37). Hydroxylation of geranylacetone and nerylacetone by Glomerella cingulata (after [137,138])... 

It is worth noting that comparable results for geranylacetone (entry 1) are reported only through reduction with stoichiometric amounts of polymethylhy-droxysiloxane (PMHS) in the presence of catalytic amount of active zinc compound [31, 32]. 

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