Geranyl acetate, cyclization

Surprisingly, linalyl acetate (R = OAc) fails to undergo reduction under these conditions instead, it rapidly decomposes through cyclization and polymerization pathways.205 The same reaction conditions transform geranyl p-tolyl sulfone (R = S02C6H4Me-/ ) into a mixture of 7% reduced and 93% cyclized products within 20 hours, whereas geranyl acetate (R = OAc) gives only a 20% yield of cyclized and no reduced product (Eq. 95) 205... 

Olefink cyclizationf Reaction of geranyl acetate (1) with C6H5SeCl does not result in the desired cyclized product 4, but in 2 and 3. The latter product when... 

Okfin eycUzatUm. (Z,Z)-l,5-Cyclononadiene (1) reacts with benzeneselenenyl chloride in acetic acid buffered with NaOAc with transannular participation by the remote double bond to afiord 2 in 68% yield/ Under these conditions, geranyl acetate (3) does not afiord 6, but rather the usutd olefin addition products 4 and 5. Cyclization of 4 to 6 does occur on treatment with CF3CO2H in CH2CI2 the seleniranium ion a is probably an intermediate, since the compound analogous to 4 but lacking the CsHsSe— group fails to cyclize under these conditions. ... 

The radical cations of diene systems in cyclic molecules are also capable of reaction as demonstrated by Demnth, Roth and their coworkers. They have studied the influence of phase on the photochemical reactivity of some naturally occurring dienes. Thns the irradiation of the diene 10 in homogeneous solution (acetonitrile/water) in the presence of an electron-accepting sensitizer such as cyanonaphthalene (CN) or DCB brings about fraws,cw-isomerization only. However, when the electron transfer reaction is carried out in the presence of sodinm dodecyl sulphate, transannular hydrogen abstraction reactions yield the two prodncts 11 and 12. Similar reactivity is observed with frans-geranyl acetate 13 and all-trawi-famesyl acetate 14. The authors report that these cyclizations are the flrst examples of biomimetic processes brought about under SET conditions. 

Japanese chemists have reported a stereoselective synthesis of humulene (9), an 11-membered cyclic sesquiterpene, by intramolecular a-alkylation of a keto group by a jr-allylpalladium complex. The starting material (7) was derived from geranyl acetate. In this case, the efficiency of the cyclization was markedly improved by addition of a diphosphine ligand such as l,3-bis(diphenylphosphino)-... 

For the synthesis of sarcinaxanthin (441) in racemic form a biomimetic, acid-promoted prenylation reaction has been described. The key step was the alkylation-cyclization of geranyl acetate (214) with the isoprene epoxide 215 to give, in a mixture, 216 with the desired 2,6-cw-stereochemistry. The primary alcohol group was transformed to the corresponding mesylate which was dehydrated and subsequent hydrolysis gave 217. Conversion of 217 into the sulphone 218 was achieved by preparation of the corresponding mesylate, followed by... 

We present here some significant examples in cyclization using Pd-catalyzed allyla-tion, in carbocycle and macrolide chemistry. Humulene, a fundamental monocyclic sesquiterpene, is derived biologically from famesol by anti-Markownikov cyclization no synthesis of this terpene by such cyclization had been realized before the highly stereoselective synthesis presented by Yamamoto and co-workers. The acyclic sesquiterpene skeleton was constructed starting with geranyl acetate via the ( ,ii)-bromide 316, which... 

The kinetics of the solvolysis of linalyl p-nitrobenzoate were published in note form 18 years ago, but a full discussion of the reaction, including the mechanism for retention of optical activity in the cyclized products, has now been published as one of the Winstein memorial papers. Another paper on the reaction of linalool with phosphorus pentachloride reports 88 % yield of a ca. 3 1 mixture of geranyl and linalyl chlorides (after 4 h at —10 °C). Acetylation of linalool is notoriously fickle on account of ready rearrangements now a method using t-butyl acetate and sodium methoxide is said to give a 90% yield of the unrearranged acetate. The rearrangements involved in the acid decomposition of the... 

The formation of oxygenated derivatives usually involves oxygenation of the parental hydrocarbons. The essential oil of Artemisia absinthum contains /-sabinyl acetate (42%) (20), geranyl pyrophosphate with a soluble enzyme, is the key cyclic precursor of 3-thujone and other C-3-oxygenated... 

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