Bornyl derivatives

Most reports on diastereoselective oxidation of sulfides are substrate-directed. Diastereoselectivity has been achieved by either steric- or neighboring-group participation.21 Incipient hydrogen bonding between the substrate hydroxyl group and the incoming percarboxylic acid has been evoked to explain the high diastereoselectivity observed in the oxidation of 10-exo-hydroxy-bornyl- derivatives 7 and 9 (Scheme 1). The oxidation of 9 with m-CPBA in MeOH occurs without stereoselectivity. 

However, both J. M. Harris and we, in independent studies, have now concluded that solvent participation is not a significant factor in the solvolysis of endo-norbornyl tosylate in solvents of moderate or low nucleophilicities42,43. Consequently, we can no longer account for the similarity in the behavior of secondary and tertiary 2-nor-bornyl derivatives in terms of the fortuitous presence of comparable solvent participation in enoto-norbornyl and carbon participation in exonorbornyl, both of which vanish in the tertiaries, resulting in essentially constant tertiary/secondary rate ratios40,41. ... 

This study supported the interpretation that there are some involvement of extra stabilization (non-classical ions) in the solvolysis of ero-substituted bornyl derivatives. 

The structures, stabilities, and Si NMR chemical shifts for pairs of silabicyclo[2.2.2]octyl and a pair of silanor-bornyl derivatives, 50/51, 52/53, and 54/55, all show that introduction of the /3-SiMe group stabilizes the cation and decreases pyramidalization at the cation center, consistent with the well-known stability of /3-silyl versus /3-alkyl carbenium ions <2003JOC1827>. 

Similarly solvolysis of bornyl derivatives and deamination of bornyl amine produce tricyclene is low yield 98,185,186). As in the deamination of isobutylamine, the yield of 1,3-hydrogen elimination increases when the carbonium ion is generated in a non-polar solvent (diglyme), in this case from the tosylhydrazone 187). That the formation of tricyclene... 

Ordinary commercial camphor is (-i-)-cam phor, from the wood of the camphor tree. Cinnamonum camphora. Camphor is of great technical importance, being used in the manufacture of celluloid and explosives, and for medical purposes, /t is manufactured from pinene through bornyl chloride to camphene, which is either directly oxidized to camphor or is hydrated to isoborneol, which is then oxidized to camphor. A large number of camphor derivatives have been prepared, including halogen, nitro and hydroxy derivatives and sulphonic acids. 

Helquist et al. [129] have reported molecular mechanics calculations to predict the suitability of a number of chiral-substituted phenanthrolines and their corresponding palladium-complexes for use in asymmetric nucleophilic substitutions of allylic acetates. Good correlation was obtained with experimental results, the highest levels of asymmetric induction being predicted and obtained with a readily available 2-(2-bornyl)-phenanthroline ligand (90 in Scheme 50). Kocovsky et al. [130] prepared a series of chiral bipyridines, also derived from monoterpene (namely pinocarvone or myrtenal). They synthesized and characterized corresponding Mo complexes, which were found to be moderately enantioselective in allylic substitution (up to 22%). 

Bornafix, 24 528 Borneols, 24 510, 527-528 Born—Haber cycle, 3 413 Born—Oppenheimer approximation, 16 736 Bornyl, 24 479 Borocarbides, 23 851 Borofluorides, 4 150 Borogypsum, 4 593 Borohydride derivatives, 13 614 Borohydride reduction effluent treatment, 9 432 34... 

Another potentially important fermentation is that producing butyric acid. The process is used industrially on only a small scale at present and details have not been disclosed. Many derivatives of butyric acid are used industrially the benzyl, methyl, octyl and terpenyl esters are used in the perfumery and essence trade and amyl butyrate, bornyl and isobornyl butyrates have been described as plasticizers for cellulose esters. Moreover vinyl butyrate is a possible ingredient of polymerizable materials. The mixed acetic and butyric acid esters of polysaccharides are also coming into favor. Cellulose acetate butyrate is marketed as an ingredient of lacquer and is less inflammable than the pure acetate. Dextran (see below) acetate butyrate may have similar uses. 

Esters mainly derived from cyclic terpene alcohols, especially the acetates, are common fragrance and flavor components. Menthanyl, menthenyl, bicyclic bornyl acetates and a few acetates of sesquiterpene alcohols are extensively used in perfume and aroma compositions. 

Fig. 6.16 Data from derivative cyclic voltammetry for the dimerisation of the radical anions of (-)-bornyl cinnamate. The rate constant, kjim/ obtained by matching the two scales is 5.6 x 102 M-1 s 1. Reprinted with permission [38],...

Fig. 5-3. Examples of mono- and sesquiterpenes and their derivatives in softwood. 1, a-Pinene 2, /3-pinene 3, 3-carene 4, camphene 5, borneol (R = H), bornyl acetate (R = COCH3) 6, limonene 7, a-terpineol 8, dipentene 9, a-muurolene 10, 8-cadinene 11, a-cadinol 12, a-cedrene 13, longifolene 14, juniperol.

Very recently, the enantioselective protonation of simple enolates was developed [41] using diastereoisomerically pure y-hydroxyselenoxides, derived from the 2-exo-hydroxy-lO-bornyl group, as chiral compounds. The selenoxides 84, containing various aryl groups, were prepared by treatment of the corresponding isomerically pure chloroselenuranes 85 with sodium hydrogen carbonate [41c] (Eq. 17 ... 

Enantioselective carbenoid cyclopropanation of achiral alkenes can be achieved with a chiral diazocarbonyl compound and/or chiral catalyst. In general, very low levels of asymmetric induction are obtained, when a combination of an achiral copper or rhodium catalyst and a chiral diazoacetic ester (e.g. menthyl or bornyl ester ) or a chiral diazoacetamide ° (see Section 1.2.1.2.4.2.6.3.3., Table 14, entry 3) is applied. A notable exception is provided by the cyclopropanation of styrene with [(3/ )-4,4-dimethyl-2-oxotetrahydro-3-furyl] ( )-2-diazo-4-phenylbut-3-enoate to give 5 with several rhodium(II) carboxylate catalysts, asymmetric induction gave de values of 69-97%. ° Ester residues derived from a-hydroxy esters other than ( —)-(7 )-pantolactone are not as equally well suited as chiral auxiliaries for example, catalysis by the corresponding rhodium(II) (S )-lactate provides (lS, 2S )-5 with a de value of 67%. 

Simpler, open-chain, chiral alkenes have also been employed in [3 + 2]-cycloaddition reactions in order to obtain face selectivity of the addition. The introduction of chiral alcohols such as ( —)-(l/ ,27 ,5S)-menthol into acrylic esters provides a simple entry into this field however, the conformational variability of such molecules allows for only relatively low stereoselectivities.The same is true for the (— )-(l /J,2i ,4i )-bornyl and (— )-(l 7 ,27 ,55)-8-phenylmenthyl derivatives. ... 

An efficient route to 7-oxocamphene involved as its key step the solvolytic rearrangement of 3,3-ethylenedioxyisobomyl tosylate (derived from camphor-quinone).621 Brief (3 min 0 °C) treatment (PCl5-CaC03) of borneol gave excellent yields of camphene hydrochloride longer reaction times gave bornyl chlorides.522... 

As noted in an earlier section, the labeling patterns of several monoterpenes derived in vivo from basic precursors such as [2-ll C]mevalonic acid are consistent with the basic cyclization scheme (Figure 1). More recently, the labeling patterns of antipodal bornane and pinene monoterpenes from [1-3H]geranyl pyrophosphate have been determined ((+)- and (-)-bornyl... 

Two groups have investigated N-sulfonyl imines of glyoxylate esters, derived from scalemic alcohols, in Diels-Alder reactions [67b, 73]. Prato and coworkers reported that glyoxylate N-sulfonyl imines bearing (-)-menthyl, (-)-bornyl and (-)-8-phenylmethyl auxiliaries reacted with cydopentadiene either thermally or using Lewis acids to give only very modest diastereomeric product ratios (56 44, 53 47,60 40, respectively) [67b]. 

The camphorsultam-derived sulfonamide is found to be the most successful system out of a variety investigated, in terms of the stereocontrol available71. Esters derived from terpenoid alcohols tend to be less fruitful, although the 8-phenylmenthyl and (diphenylmethyl)bornyl residues do have quite a substantial influence. 

---