Pinene derivative

E = CIC02Me, CICONMe2 Scheme 13.9. Regio- and stereoselective formation of p-pinene derivatives from nopadiene... 

Dimers with a 1,2-bismethylenecyclobutane structure were obtained from 585 [240], 590 [238], 591 [241], 592 [242], 593 [243] and from the pinene derivative 597 [244]. The interception of 592 by 1,3-diphenylisobenzofuran (DPIBF) afforded two diastereomeric [4+ 2]-cycloadducts [245], Bicyclo[5.1.0]octa-3,4-diene (594) was generated by /3-elimination and trapped by sodium pyrrolidide because of the question of the extent to which the corresponding bicyclooctyne is formed in addition to 594 [184], Liberated by /3-elimination from ll,ll-dichloro-l,6-methano[10]annulene in... 

Table 9. Cleavage of Four-Membered-Ring-Annulated Pinene Derivatives.165...

Synthetic pine oil is produced by the acid-catalyzed hydration of mainly a-pinene derived from sulfate turpentine, followed by distillation of the crude mixture of hydrocarbons and alcohols. The predominant alcohol obtained is a-terpineol, although under the usual conditions of the reaction, reversible and dehydration reactions lead to multiple hydrocarbon and alcohol components (Fig. 1). 

Dihydroxylation of hindered double bonds. The a-pinene derivative 1 (Nopol) is hydroxylated in low yield by osmium tctroxide and f-butyl hydroperoxide. Hydroxylation is effecled in 62% yield by use of 0s04 in combination with trimethylamine N-oxide as oxidant and pyridine as base. This method is generally suitable for hindered alkenes (yields 78-93%). 

Also the biotransformation of a-pinene derivatives and other pinane monoterpenoids by Cephalosporium aphidicola has been described [101]. The best conversion was the oxidation of verbenol to verbenone (yield 61%). 

Feverfew contains flavonoid glycosides, monoterpenes (eg, camphor, other pinene derivatives), and sesquiterpene lactones. The most prevalent sesquiterpene is parthenolide, which is primarily found in the seeds and leaves of the plant, with concentrations ranging from 1% to 3%. 

However, it could be shown that in principle simple imines can be used successfully as well for asymmetric aminoalkylation reactions catalyzed by chiral Lewis acids. The asymmetric allylation of simple imines 16 with allyltributylstannane (Scheme 6) catalyzed by the / -pinene derivative 17 [32a], for example furnished comparatively good results (for related asymmetric catalytic allylations of simple imines, see [32b-d]). Moreover, it was demonstrated on the basis of several Strecker-type syntheses [33-35] that catalysts such as the chiral aluminum complex 18 (Scheme 6) [33a—b] are also well suited for enantioselective aminoalkylations with simple imines. The mechanism indicated in Scheme 6 shows that the... 

Planar chiral compounds should also be accessible from the chiral pool. An example (with limited stereoselectivity) of such an approach is the formation of a ferrocene derivative from a -pinene-derived cyclopentadiene (see Sect. 4.3.1.3 [81]). A Cj-symmetric binuclear compound (although not strictly from the chiral pool, but obtained by resolution) has also been mentioned [86]. Another possibility should be to use the central chiral tertiary amines derived from menthone or pinene (see Sect. 4.3.1.3 [75, 76]) as starting materials for the lithiation reaction. In these compounds, the methyl group at the chiral carbon of iV,iV-dimethyl-l-ferrocenyl-ethylamine is replaced by bulky terpene moieties, e.g., the menthane system (Fig. 4-2 le). It was expected that the increase in steric bulk would also increase the enantioselectivity over the 96 4 ratio, as indicated by the results with the isopropyl substituent [118]. However, the opposite was observed almost all selectivity was lost, and lithiation also occurred in the position 3 and in the other ring [134]. Obviously, there exists a limit in bulkiness, where blocking of the 2-position prevents the chelate stabilization of the lithium by the lone pair of the nitrogen. 

From the range of synthetic applications of Brown s pinene-derived allyl- and crotylborane reagents illustrated in these selected examples, it is clear that they are excellent reagents for the synthesis of chiral homoallylic alcohols from chiral and achiral aldehydes alike. That so many researchers have applied these reagents in their research also attests to the great utility of these reagents in organic synthesis. 

Of the oxidised pinene derivatives, the n.m.r. spectra of the pinanols [2-hydroxypinanes, (245)] have been discussed by Coxon et the spectral... 

The remarkable difference between the a-pinene derived reagent and the nopol derived reagent appears to be due to steric factors. 

The increased steric requirement of the 2-(benzyloxy)ethyl side chain provides a somewhat more selective reagent. Similar results can be achieved by replacing the 2-methyl group of the a-pinene derived reagent with an ethyl or propyl group12. The latter reagents are prepared by hydroboration of the appropriate alkene, available from nopol12, with solid 9-BBN for 6 hours at 65 =C. 

Another method for asymmetric alkylation of a masked glycine was reported by Yamada, and is shown in Scheme 3.13 [72]. In this example of a chiral glycine enolate, the Schiff base of tert-hniy glycine and an a-pinene-derived ketone is dilithiated with two equivalents of LDA. Presumably, the lithium alkoxide is chelat-... 

In the case of the pinene-derived acyl nitroxide 31 [50], as well as the phthalimide-iV-oxyl radical 32 [56], the mechanism of the oxidation involves hydrogen abstraction by the reactive acyl nitroxide [58] (or phthalimidyl nitroxide), followed by trapping of the resulting carbon radical with either a second equivalent of nitroxide or by molecular oxygen (Scheme 19). Table 2 summarizes the results of oxidative desymmetrization using optically active nitroxides. 

Among the pinene-derived mono-alcohols, only (-)-isopinocampheol [(— )-33] has been used as an auxiliary. Its enantiomer ( + )-33 is commercially available or is readily prepared by a hydroboration/oxidation sequence from (+)-a-pinene (for a detailed procedure, see ref 34). The phenyl ether of (—)-33 has been used as a starting material for cyclic enol ethers 35. obtained by Birch reduction of the phenyl group3s, which are used as chiral dienes in Diels-Alder reactions (Section D.1.6.1.1.1.), although no description of the synthesis of the ether has been given. The alcohol has also been used for the synthesis of di(isopinocampheyloxy)-2-propenylborane 3433 (Section D.2.3.5.). 

From (+)-limonene, a hydroboration product, limonylborane (32). was obtained and used in asymmetric allylboration reactions, but with less success than the pinene-derived reagents34 (Section D.2.5.2.). 

An example of an enantiomerically pure polymer is also shown [11]. Aoki et al. showed that films of a polyacetylene substituted with a (-)-p-pinene derivative formed an effective membrane for chromatographic resolutions of racemic mixtures. ( )-2-Butanol was resolved to 29.8% eje. and unsaturated polymers for both liquid-phase and gas-phase separation applications (8, 9, 79]. It has been suggested that the rigidity and irregularity of the highly substituted polyacetylene chain, combined with the presence of aliphatic substituents which reduce interchain interactions, are important for the polymers transport properties [10]. 

P-14 - Synthesis of a-pinene derivatives using redox-mesoporous molecular sieves... 

Alpha-Pinene derivatives 23-P-14 Propyl alcohols oxidation 27-P-08... 

Cis addition of acetate and methoxide has been observed for the reaction of Pd salts with a pinene derivative (Scheme 6.66). Although the corresponding complexes containing the Pd-OR moieties were not detected, the stereochemistry of the final complex is indicative of inserhon [208]. 

The influence of substitution on the alkenes (49) has been assessed. The study has shown that styrenes with 6>-methyl and oc-methyl groups adopt orthogonal geometry. This results in a blue shift in the tttt transition.The ocimene derivative (50) is formed on irradiation of the pinene derivative (51). There is no evidence for [2 + 2]-cycloaddition, and the rearrangement occurs on irradiation in benzene or methanol. Excitation results in triplet energy transfer from the benzene moiety to the pinene. The ring opening affords the cis isomer (50), but continued irradiation affords a ratio, trans xis, of 52 ... 

Formation of TT-allylpalladium complexes from alkenes and PdCl2, and the reaction of the complexes with carbon nucleophiles constitutes alkylation of alkenes with carbon nucleophiles via TT-allylpalladium complexes as a stoichiometric reaction, offering a method of oxidative functionalization of alkenes, and can be applied to syntheses of a number of natural products [85]. For example, functionalization of pinene (186) was carried out via the reaction of the TT-allylpalladium 187 with a phenylsulfinyl group to give 188, and converted to the pinene derivative 189 [86]. TT-Allyl complex formation takes place particularly easily from the a, - or unsaturated carbonyl compounds. The reaction of the complex 191, formed from 3-penten-2-one (190), with a carbon nucleophile to lead to 192 is an example of y-alkylation of a,jS-unsaturated ketones or esters [87]. 

The addition of thiols to terpenes, e.g., limonene and pinene have been studied (3). This is a simple approach to synthesize a wide range of alcohol or ester functionalized renewable monomers. The endocycUc and exocyclic double bonds of the limonene monomers exhibit different reactivities. By a variation of the thiol feed ratio monoaddition or diaddition products can be obtained. Similarity, pinene derivates can be prepared. 

In the case of the less sterically demanding aliphatic 21.131 [e.g. R = CH20Bn) and cyclic epoxides 21.136, the selectivity with these catalysts dropped to a modest level and helow. Cyclooctene oxide 21.136 ( = 8) proved to be a particularly difficult substrate, displaying low reactivity and selectivity with most of the Lewis bases except for the pinene-derived bipyridine mono-AT-oxide 21.23, which furnished the corresponding chlorohydrin in 90% ee. Catalyst 21.23 was also active with other cyclic... 

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