Hydrophenanthrene

Composition. Rosin is primarily a complex mixture of monocarboxyUc acids of alkylated hydrophenanthrene nuclei. These constituents, known as resin acids, represent about 90% of rosin. The resin acids are subdivided into two types, based on their skeletal stmcture. The abietic-type acids contain an isopropyl group pendent from the carbon numbered 13. The pimaric-type acids have a methyl and vinyl group pendent from the same carbon atom. Figure 1 shows the stmcture of typical resin acids abietic acid, C2QH2QO2 (1) is predominant. The remaining 10% of commercial rosin consists of neutral materials that are either hydrocarbons or saponifiable esters. These materials are derived from resin acids by decarboxylation or esterification. 

Trauner, D., Bats, J.W., Werner, A., Mulzer, J. (1998) Synthesis of EnantiomericaUy Pure Morphine Alkaloids The Hydrophenanthrene Route. Journal of Organic Chemistry, 63, 5908-5918. 

Our earlier studies [2,3] have measured the reactivity of both hydrocarbon and nonhydrocarbon acceptors with good donor solvents (Tetralin, hydrophenanthrenes), and poor donors (mesitylene). Although the primary role of solvents was... 

Sym-octahydrophenanthrene (HgPh) would be expected to follow the same rearrangement-dehydrogenation reactions as Tetralin, except with more isomer and product possibilities. The reactions shown in Figure 1 illustrate the many structures expected from sym-HgPh in the presence of free radical acceptors. Unlike Tetralin, hydrophenanthrenes have multiple structures which each, in turn, form various isomers. The amounts of these isomers are dependent upon the type of hydrogen-transfer reactions and the environment of the system. 

The presence of hydrophenanthrene isomers was indicated by the observation of numerous GLC peaks with identical parent ions but different fragment ions in their mass spectra. Compounds with methyl substituents always have more intense M -15 ions than those with unsubstituted six-membered rings. Considering the complexity of the total reaction mixtures, liquid chromatography (HPLC) was used to concentrate more discrete solvent fractions for C-NMR study. 

A sample of hydrophenanthrenes from a dibenzyl hydrogen-transfer reaction was separated by liquid chromatography into seven fractions. Each fraction (>20 mg) was then analyzed... 

Figure 12.5 Cholesterol ester. Cholesterol is a derivative of the cyclopentanoper-hydrophenanthrene condensed ring system and is therefore a member of the group of compounds called steroids. It often occurs esterified at position 3 with a long chain fatty acid, which may be saturated or unsaturated and commonly contains 16 or 18 carbon atoms. Steroids that form esters in this way are more correctly called sterols.

A classical application of cyclopropane rings in "reactivity inversion", in which a previously negatively polarised y-carbon atom (see 29) to a carbonyl group is inverted by formation of a cyclopropane ring (30) and is then intramolecularly attacked by a nucleophilic aromatic ring, is found in the synthesis of hydrophenanthrene system 11 (Scheme 5.19) developed by Stork in 1969 [21]. 

Table DC summarises the data for experiments operated at 42(PC for 2 h at the three stirrer speeds 200,400 and 600 rpm. It can be seen that the values are closest to unity at 600 rpm, a value of one, indicating equal performance. The autoclave providing the higher conversion of phenanthrene also showed the higher ability for hydrogenation. The values relating to cracking were inconclusive, but did show the near unity vadue at 6(X) rpm. The extent of conversion tended to increase with increasing stirrer speed, as did the amount of hydrogenation with the contents of all the hydrophenanthrenes increasing, but the amount of hydrocracking tended to decrease.

Cracking reactions produced only 3.5% of the product and most of the cracked product was substituted hydrophenanthrenes. One product positively identified was s-HgP resulting from the initial hydrocracking of one or both of the forms of decahydrophenanthrene which have low resonance stabilisation eneigies. This type of cracking reaction would not be unfavourable and could produce a better hydrogen donor compound. 

Phenanthrene is converted to partially and totally reduced phenanthrene by catalytic hydrogenation [415, 416, 417], Partial reduction to 1,2,3,4-tetra-hydrophenanthrene can also be achieved by sodium [418. ... 

We have found that intramolecular Friedel-Crafts alkylations of conjugated dienones permit the efficient preparation of functionalized hydrophenanthrenes (Equation 5.1).21 Since this represents a new strategy for the synthesis of 6,6,6-fused tricycles, we sought to demonstrate its utility through the total syntheses of miltirone (56) and two closely related diterpenoids sageone (57), which possesses significant antiviral activity,22 and arucadiol (58), 23... 

An intramolecular Friedel-Crafts alkylation to prepare functionalized hydrophenanthrenes. (From Majetich, G., Liu, S., Fang, J., Siesel, D., and Zhang, Y.,. Org. Chem.., 1997, 62, 6928. With permission.)... 

Dehydroabietic acid 1, the main resin acid of disproportionated rosin, is a readily available hydrophenanthrene derivative and a useful starting material for the synthesis of industrial and/or physiologically important products (1), by introduction of suitable substituents in the aromatic ring, such as the nitro or amino groups. 

The stilbenes have played a crucial role in the development of modern photochemistry. Direct or triplet sensitized irradiation of trans-stilbene (t-1) in dilute solution results in isomerization to cis-stilbene (c-1) as the exclusive uni-molecular photochemical reaction (1-3). Direct irradiation of c-1 results in isomerization to both t-1 and trans-4a,4b-di-hydrophenanthrene (2), which revert to c-1 both thermally and photochemically and can be trapped by oxidants such as iodine or oxygen to yield phenanthrene (3) (4-6). Triplet sensitized irradiation of c-1 yields only t-1. These unimolecular isomerization pathways are summarized in eq. 1. 

The product yields by carbon number are plotted in Figure 6. At all except the most severe conditions studied,the major component in the gas phase was n-butane. This observation is consistent with the a-ring opening and dealkylation mechanism proposed for tetra-and octa-hydrophenanthrene cracking. At the most severe conditions ethane was present in the greatest quantities. This can be explained by side chain cracking of n-butylbenzene according to the Rice-Kossiakoff mechanism or by secondary reactions of the n-butane. 

The most interesting part of this synthesis is the cyclialkylation-based strategy for the synthesis of functionalized hydrophenanthrene. The utility of this methodology is featured in the synthesis of many diterpenoids. 

Scheme 11.19 Hydrogenation of phenanthrene to hydrophenanthrenes over Raney Ni.

Similar results were obtained with a structurally related hydrophenanthrene system119. 

The clositig of a six-membered ring by this process is possible when favored by structural rigidity of the molecule as in the preparation of 9,10 hydrophenanthrene from phenyllithium and 2,2 -di-(bromomethyl)-biphenyl. ... 

---