Ketone racemic camphor

Dissolving metal reduction of camphor produces a mixture of bor-neol, isobomeol, and pinacol coupling products (Scheme 39). The ratios of the stereoisomers are affected profoundly by whether the starting ketone is enantiomerically pure or racemic, implying the chirality recognition at the stage of ketyl radical (65). 

Metal-ammonia reduction of ketones. Swiss chemists have reported a detailed study of the mechanism of this reaction, using for the most part (-l-)- 3,3-D2] camphor as substrate. The conclusions drawn have some useful practical applications. The choice of metal (Li, Na, or K) has little effect on the course of reduction to the thermodynamically more stable diastereoisomeric alcohol. The most important conclusion is that pinacol reduction can be suppressed completely in Na-NH3 reductions by use of ammonium chloride as the proton source, a finding first reported by Murphy and Sullivan.2 This salt also partially suppresses pinacol formation in Li-NHj reductions. It also suppresses reduction of enolates, and thus should decrease racemization in reduction of chiral ketones. 

A useful synthesis (ref.ll)of patchouli alcohol, an important fragrant constituent of patchouli oil, from (+)-camphor, that onetime important natural product which was employed as a plasticiser for nitrocellulose (itself a semi-synthetic polymer), was complicated by structural revision of the sesquiterpene alcohol. Dihydrocarvone (14) obtained by saturation of the ring double bond in carvone, a major constituent of oil of spearmint has been employed for two very different sesquiterpenes, the ketone campherenone (15) and the alcohol, occidentalol (16). In the first case an enol acetate was converted to a bicyclic intermediate by earlier established methodology and the route emulated a plausible biogenetic sequence giving racemic campherenone (ref.12) as shown. Any chirality in (14) is apparently lost. 

Chemical Abstracts Service Registry Numbers CAS 464-48-2 and CAS 464-49-3 (optical isomers) CAS 21368-68-3 (racemic mixture) Synonyms Campho-phenique Musterole Ben-Gay children s vaporizing rub Vicks Vaporub Vicks Vaposteam Heet Sloan s Liniment Camphorated oil Camphor spirits Chemical/Pharmaceutical/Other Class Cyclic ketone of the hydroaromatic terpene group Chemical Formula CioHi O... 

Camphor a bicyclic monoterpene ketone found widely in plants. Both optical isomers occur naturally (-t)-C. (Japan C), m.p. 180°C, b.p. 204°C, [a] -h43.8° (c = 7.5 in abs. ethanol), and (-)-C. (Matricaria C), m.p. 178.6°C, b.p. 204°C, [o]g -44.2° (ethanol). C. is obtained commercially from camphor trees (Cin-namomum camphora) native to coastal areas of East Asia. Partial synthesis from pinene is also commercially important, the product being a racemic mixture... 

A terpene is pieseiit in the oil, and two isomeiic ketones which have been named a-santolmenone and )3-santolinenone, ot the formula CioHieO, both of which aie unsatuiated A saturated ketone of the camphor type of the same formula is also piesent a-santohnenone appears to be an optically inactive, racemic ketone, and )8-SAntolmenone is also optically inactive and probably lacemic... 

The reduction of cyclohexane-l,2-dione 38 (Figure 21.12) gave racemic trans-cyclohexane-l,2-diol 39 [179, 180]. From the reduction of camphorquinone 40, a 63% yield [96] of cxo-2-hydroxy camphor 41 and 3-hydroxy camphor 42 was obtained. In addition, the reduction of substituted acenaphthenequinones afforded the corresponding 2-hydroxyacenaphthenones in 24-48% yields with 10-93% ee [181]. The Wieland-Miescher ketone has also been reduced with high enantioselectivity [182]. 

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