Caranes

Metals (Raney nickel or Ni/Si02, Pd/C,...) can easily catalyze the isomerization of 3-carene into 2-carene (Scheme 44), but the selectivity is low, due to the hydrogenation of the two isomers into carane. 

Similarly, photolysis of (+) - cis -caran - 5 - one yielded the following products 1045 ... 

Dichlorocarbene has been generated under solid-liquid conditions by use of micro-waves. Heating a mixture of CHC13, powdered NaOH, and trace amounts of CTAB under reflux in cyclohexene with microwave irradiation afforded 90% dichloronor-carane (Eq. 50) within 20 min, compared with 81% in 60 min without microwave exposure, or only 12% in 90 min without the catalyst. 

This reaction has also opened a rapid access to various polycyclic compounds, as illustrated by the transformation of a mixture of diastereomers 373 into tricyclic compound 374 as a single diastereomer, through a completely stereo-convergent process (Scheme 92). Interesting entries into the syntheses of carane family natural products have also been disclosed by Ftirstner with AuC 331 and by Marco-Contelles with PtCl2.332... 

Scheme 2 Optical resolution with /-menthol and carane-3,4-diol...

As a result, the ester (24) of (IS,3R,4R,6R)-carane-3,4-diol (23) with (1 /(.S W/Y/n.s-chrysanthemic acid could easily be separated by silica gel column chromatography to give two ester diastereomers. The Rf value of the ester of... 

S,3//,4/C6//)-carane-3,4-diol with (l/ )-tra s-chrysanthemic acid is 0.62, and the Rf. value of the corresponding ( l,S )-/ra .v-chrysanthemic acid ester is 0.65 (toluene ethyl acetate = 3 1). However, the /-menthol ester of (1 /. S )-/ra .v-chrysanthemic acid could not easily be separated by silica gel column chromatography to obtain (1 AfWran.v-chrysanthemic acid /-menthol ester. 

Optical resolution methods with carane-3,4-diol are noteworthy for wide generality. Esters of various cyclopropane carboxylic acids with (1,S, 3A>,4A>,6A>)-carane-3,4-diol were prepared and all (lR)-isomers could easily be obtained by a simple silica gel column chromatography. 

Convert (+) A3 carene to (+) trans-4-acetoxycarane (I) via (+) trans-4-OH-carane. Reflux 50 g (I) for 45 minutes (180° C oil bath under N2 or Argon). Cool and can distill (57/10) to get about 25 g mixture of A3 and A4 carene (residue is unchanged starting material) containing about 60% A4 isomer. 

Lochynski, S., Kowalska, K. and Wawrzenczyk, C., Synthesis and odour characteristics of new derivatives from the carane system. Flavour Fragr. J., 2002, 3, 181-186. 

Cl wopwaiioripaweanirietoiteinefA Progrema tn OerTvce SaNrir 4nc CvNoein Caran)i ri IPCS SOOO... 

Other papers in this section report catalytic hydrogenolysis of cis- and trans-caranes to m- and p-menthanes, ° the stereochemistry of amines derived from... 

Carane-type monoterpenes possess a cyclopropane ring in a bicyclo[4.1.0] skeleton. d-3-Carene 10 is a common constituent in various essential oils. 

For a review of rearrangements in bicyclic systems, see Hogevcen van Kruchlen Top. Curr. Chem. 1979, 80, 89-124. For reviews concerning caranes and pinancs see, respectively, Arbuzov Isaeva Russ. Chem. Rev. 1976, 45, 673-683 Banthorpe Whittaker Q. Rev. Chem. Soc. 1966, 20. 373-387. 

Photomutarotation, in addition to inversion of the rotatory dispersion curves, is observed on exposure of ( —)-2-chloro-nitrosocamphane (LXXXIX) to intense light.114,187 On the other hand, isomerization of the normal iso-type without the inversion of the rotatory dispersion curves is involved in the case of 2-chloro-2-nitroso derivatives of pino-camphane (XC), carane (XCI), and p-menthane (XCII).116... 

Methylene source Reaction conditions Nor- carane Products, % 3 Me 4 Me Hexene Hexene 1 Me Hexene Ref. 

Carene can in theory undergo hydrogenation to give either dx-carane or (nms-carane. 

The exclusive product is m-carane, since it corresponds to transfer of hydrogen from the less hindered side. 

Preliminary testing of the two schemes for configurational names indicates strong preference for the a,p method. Although this method was applied above only to bornane-type bicyclics, it can be applied equally as well to configurational names for the other fundamental bicyclic structures — that is, the thujane, carane, and pinane types. The reference point of these structures could be the same as in the case of bomane — that is, the. most substituted bridge carbon atom. For example ... 

Therefore, on the basis of their carbon skeletons, the bicyclic terpenes belong to the following condensed ring structures tbujane type to bicycloQ3.1.0 ]hexane carane type to bicyclo Q4.1.0 ]heptane pinane type to bicyclo Q3.1.1I]heptane and... 

In general, the names used are derived from those of the species of plants in which some of the more important compounds occur. Only in certain cases is a systematic nomenclature of value in these cases, reference is made to the completely demethylated hydrocarbons of the three main groups these are called nor-carane, norpinane, and norcamphane. ... 

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. 

Rule 3. When a valence bridge — i.e., contains no carbon — is present, the ring carbon skeleton is completely numbered by Rule 2. This is the case for thujane and carane. 

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