Caran-2-one

Three independent syntheses of the cubebane-type skeleton have been reported in which formation of the cyclopropane ring was once again achieved by an internal diazoketone cyclisation. In the first of these syntheses, Yoshikoshi et utilised (—)-trans-caran-2-one as the starting material which was converted in three steps to the spiro-lactone (83). Pyrolytic rearrangement of this compound to the key olefin-acid (84) was accomplished in 70% yield. Conversion to the corresponding diazoketone, followed by decomposition yielded the tricyclic ketone (85, R = O) and its stereoisomer (86). Standard procedures converted... 

N.m.r. chemical shifts of a number of monoterpenoids of this class are included in a study of bicyclo[4,l,0]heptanes. A further paper in a series on enthalpies of combustion and formation concerns the 3,4-epoxycaranes. (+)-Car-2-ene and (—)-car-2-ene of high optical purity have been synthesized from the respective (-)- and (+)-rran5-caran-2-ones, via the analogous and uncited tosylhydrazone/methyl-lithium route used by Cocker et al. for synthesizing (—)-cw-car-4-ene (Vol. 1, p. 47), thus providing access (Vol. 2, p. 29, ref. 108) from the readily available (+)- and (-)-dihydrocarvones. Cocker et al. have synthesized norcaran-3-one via dibromocarbene addition to 4,4-dimethoxy-cyclohexene and treatment with lithium dimethylcuprate) from which car-2-ene, car-3-ene, and car-3(10)-ene were prepared. ... 

M-)copoerie ReJaJed compd i -) mustakone = oxocopaene ) [/] 2. -) cub8b camphor (cubeboD (-)/ j-caran-2-one... 

Car-3-ene, A35 Car-4-ene, T5 /raw5-car-4-ene-3- ol, T6 Caracurine VII, K12 fraw5-caran-2-one, T6 Caranes, T6 Caranine, K6 Carbodiimides, X3 Carbomycin, Y25 Carbonates, A14-15 Carbonyls, X9, X2, Zl / -carboxybutyramide, A34 Cardenolides, T49 Cardiolipin, A15 Carlosic acid, A12 Carminomycin, Y28 Carnitine, A2 Carnosine, A20 Carnosol, T33 Carolic acid, A12 ... 

Rule 2. One bridge-end carbon is No. 1, and the numbering proceeds clockwise around the entire ring skeleton, first by the longer route to the other bridge-end carbon and then by the shorter route back to carbon No. 1. Hence, in thujane and pinane, the bridge ends are 1-5 instead of 1-3 in carane, 1-6 instead of 1-3 in bornane, 1-4. 

A review of the class635 and a detailed conformational analysis of the carane-2,3-diols636 have appeared. No new naturally occurring carane derivatives, or any unusual sources of known compounds, have been reported, but much detailed chemistry based on (+ )-car-3-ene has been carried out directed towards the commercial exploitation of this major component of Indian turpentine. Syntheses of car-2-, car-3-, and car-3(10)-enes from cyclohex-3-en-l-one have been developed.637... 

Further papers in this section include a straightforward synthesis of 4-methyl-car-3-ene and some derivatives, another report of cobalt-catalysed air oxidation of car-3-ene cf. Vol. 7, p. 45), anodic oxidation of car-3-ene to yield 2,6,6-trimethylcyclohepta-2,4-dienol predominantly (together with some p-menthane derivatives), a further paper cf. Vol. 8, p. 57) on dehydrogenation of car-3-ene over chromia and chromia-alumina catalysts, the full paper on isomerization of 2,3- and 3,4-epoxycaranes over solid acids and bases, dimerization of (-)-cw-caran-4-one to 4-caranylidenecarane (mostly transoid) using the diamagnetic complex [THF,Cl2Mg2Ti]2, (+)-car-3-ene nitroso-... 

For a double bond outside the ring, two prefix numbers are necessary — that of the ring carbon to which the double bond is attached, and following this in parentheses that of the substituent carbon to which the double bond is attached — e.g., 3(10)-carene(Formula 58,Chart 11) 2(10),3-pinadiene (Formula 70, Chart 12). If the number of the substituent carbon in such a double bond were the next higher-numbered carbon to the ring carbon, which is impossible on the basis of the fixed numberings of the thujane, carane, and pinane structures (see Rule 2), then only one prefix number would be necessary. 

To number the positions if double bonds are present, follow the bicyclo plan of assigning to double bonds as low positions as are consistent with the numbering imposed by the bridges. For structures containing one double bond, this means that only 2- -ene structures can exist in the thujane and pinane groups but both the 2- and 3 -ene structures can exist in the carane group. Thus ... 

Double-bond migration may lead to even more striking results. Hydrogenation of cyclohexen-2-ol over Pd affords 67% cyclohexanol and 33% cyclohexanone as a consequence of enol-ether formation after migration of the double bond . Caran is the expected product from hydrogenation of car-3-ene, 35, and the one obtained over Pt. But when the reaction is conducted over Pd, the product is quantitatively 1,1,4-trimethylcy-clopheptane, 36 ... 

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