1-Decalols

Similar fragmentations to produce S-cyclodecen-l-ones and 1,6-cyclodecadienes have employed l-tosyloxy-4a-decalols and 5-mesyloxy-l-decalyl boranes as educts. The ringfusing carbon-carbon bond was smoothly cleaved and new n-bonds were thereby formed in the macrocycle (P.S. Wharton, 1965 J.A. Marshall, 1966). The mechanism of these reactions is probably E2, and the positions of the leaving groups determine the stereochemistry of the olefinic product. 

The achiral triene chain of (a//-rrans-)-3-demethyl-famesic ester as well as its (6-cis-)-isoiner cyclize in the presence of acids to give the decalol derivative with four chirai centres whose relative configuration is well defined (P.A. Stadler, 1957 A. Escherunoser, 1959 W.S. Johnson, 1968, 1976). A monocyclic diene is formed as an intermediate (G. Stork, 1955). With more complicated 1,5-polyenes, such as squalene, oily mixtures of various cycliz-ation products are obtained. The 18,19-glycol of squalene 2,3-oxide, however, cyclized in modest yield with picric acid catalysis to give a complex tetracyclic natural product with nine chiral centres. Picric acid acts as a protic acid of medium strength whose conjugated base is non-nucleophilic. Such acids activate oxygen functions selectively (K.B. Sharpless, 1970). 

As previously described, a mixture of and J -octalins can be prepared by the reduction of naphthalene or Tetralin. Another route to this mixture is the dehydration of a mixture of 2-decalol isomers. This latter route has certain advantages in that one can avoid the handling of lithium metal and low-boiling amines. Moreover, 2-decalol is available commercially or can be prepared by the hydrogenation of 2-naphthol (5). In either case a comparable mixture of octalins is obtained, which can be purified by selective hydroboration to give the pure J -octalin (Chapter 4, Section III). 

This dry ozonation procedure is a general method for hydrox-ylation of tertiary carbon atoms in saturated compounds (Table 1). The substitution reaction occurs with predominant retention of configuration. Thus cis-decalin gives the cis-l-decalol, whereas cis- and frans-l,4-dimethylcyclohexane afford cis- and trans-1,4-dimethylcyclohexanol, respectively. The amount of epimeric alcohol formed in these ozonation reactions is usually less than 1%. The tertiary alcohols may be further oxidized to diols by repeating the ozonation however, the yields in these reactions are poorer. For instance, 1-adamantanol is oxidized to 1,3-adamantane-diol in 43% yield. Secondary alcohols are converted to the corresponding ketone. This method has been employed for the hydroxylation of tertiary positions in saturated acetates and bromides. 

Lange and Bosch<109) reported the interesting intramolecular oxetane formation shown below. Reduction with lithium aluminum hydride afforded m is-9-decalol (32%) ... 

Decalol, aroma chemical derived from naphthalene, 3 235... 

The dehydration of the four stereoisomers of 1-decalol over alumina was investigated by Schappell and Pines 66), who found that the... 

The formation of 1,9- and cis-1,2-octalin from ci5,cis-l-decalol is a clear indication of the dehydration by means of a trana elimination reaction ... 

The dehydration of cis,alumina surfaces, could readily explain the observed data ... 

As with the ci ,cis-l-decalol, tmna,cis-l-decalol, with its hydroxyl group locked in an axial position, presents the catalyst with two paths for tmws-diaxial elimination. In agreement with the previous observation, the production of the more substituted 1,9-octalin was favored over the [Pg.64]

The formation of 1,9-octalin from fraras,[Pg.65]

Humans may be programmed to be more sensitive to natural food contaminants. For instance, (-)geosmin (rrans-l,10-dimethyl-rran5-9-decalol) occurs in earth, natural surface water, and in foods in contact with soil or water, such as beets, clams, or fish. Geosmin is a microbial, fungal, or algal metabolite. It is a water pollutant and off-flavor compound. The naturally occurring (-)enantiomer has a threshold 11 times lower than the (-I-) enantiomer (Polak and Provasi, 1992). 

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