9-Methyl-9,10-dihydrophenanthrene

SET reduction of dibenzonorcaradiene (147) with lithium, sodium or potassium naphthalenide followed by quenching with water led to 9-methylphenanthrene (148) (16-24%), 9-methyl-9,10-dihydrophenanthrene (149) (33-43 %) and 6,7-dihydro-5-if-dibenzo[a,c]cycloheptane (150) (23-34%). ... 

The rates of chlorination of bridged biphenyls have also been measured and show the effect of coplanarity on reactivity. Second-order rate coefficients (104A 2) at 25 °C were fluorene (1,700), 9,10-dihydrophenanthrene (170), 1,2 3,4-di-benzocyclohepta-1,3-diene (9.70), 5-methyl-l,2 3,4-dibenzocyclohepta-l,3-diene... 

Rycroft et al. (1999) identihed the major components of plants from six locations in western Scotland and four from the Azores using nuclear magnetic resonance (NMR) fingerprinting and GC-MS. The terpene P-phellandrene [129], which may be responsible for the aroma of material crushed in the held, was detected in all specimens. The major components, which appear in Fig. 5.6, were shown to be methyl eveminate [444], the four methyl orcellinate derivatives [445 8], the two 9,10-dihydrophenanthrene derivatives [449] and [450], the newly described phthalide killamiensolide [451], and the bibenzyl [453]. Methyl eveminate was the major compound in all 10 specimens other compounds were more varied in their occurrence. Killamiensolide was not isolated as such but was detected when extracts were acetylated yielding, among other compounds, [452]. The presence of the bibenzyl compound [453] in more than trace amounts in P. killarniensis raises the possibility that it represents contamination from P. spinulosa with which it was growing at the one site. 

Isolation of Oxidation Products. After oxygen absorption had ceased, or reached the desired value, the oxidates were poured into water. In many cases the reaction product could be removed by filtration in high yield. In this manner xanthone (m.p. 172-174°C.), was isolated from oxidations of xanthene or xanthen-9-ol thioxanthone (m.p. 208-210°C.), from thioxanthene acridine (m.p. 107-109°C.), from acridan anthracene (m.p. 216-217°C.), from 9,10-dihydroanthracene phenanthrene (m.p. 95-99°C.), from 9,10-dihydrophenanthrene pyrene (m.p. 151-152.5°C.) (recrystallized from benzene) from 1,2-dihydropyrene and 4-phenan-throic acid (m.p. 169-171 °C.) (recrystallized from ethanol) by chloroform extraction of the hydrolyzed and acidified oxidate of 4,5-methyl-enephenanthrene. 

The iV-aminopyrrole - benzene ring methodology has been applied to a synthesis of the 9,10-dihydrophenanthrene juncusol (218) (81TL1775). Condensation of the tetralone (213) with pyrrolidine and reaction of the enamine with ethyl 3-methoxycarbonylazo-2-butenoate gave pyrrole (214). Diels-Alder reaction of (214) with methyl propiolate produced a 3 1 mixture of (215) and its isomer in 70% yield. Pure (215) was reduced selectively with DIBAL to the alcohol, reoxidized to aldehyde, and then treated with MCPBA to generate formate (216). Saponification to the phenol followed by O-methylation and lithium aluminum hydride reduction of the hindered ester afforded (217), an intermediate which had been converted previously to juncusol (Scheme 46). 

The study of relative migratory aptitudes of alkyl groups (Shubin et al., 1970b) began with the preparation of 9,10-dimethyl-9-ethylphenanthrenium ion [309] which was prepared from both 9-ethyl-9-methyl-10-methylene-[310] and 9,9-dimethyl-10-ethylidene-dihydrophenanthrene [311]. As shown... 

The stilbene-dihydrophenanthrene photocycllsatlon reaction continues to find synthetic applications. The tetra-oxygenated methyl phenanthrene skeleton (161) has been prepared by photocyclisation of the stilbene (162) aromatisation of the intermediate dihydrophenanthrene occurs by elimination of methanol. 2 nq photocyclisation was observed In the absence of the cyano group in this compound 2 although the closely related structures (163) and (164) are said to cyclise to the phenanthrenes (165) and (166). Triarylethylenes are important... 

Accompanied by stemofurans A-K (92-102), the bibenzyls and stilbostemins A-F (132-137), were also isolated fi-om Stemona collinsae roots together with five known derivatives -the stilbenes pinosylvin and 4-methylpinosylvin and the dihydrophenanthrene stemanthrene D (359) [57]. Stilbostemin B (133) and D (135) have been previously isolated from Stemona tuberosa [75]. The consecutively designated stilbostemin G (138) was isolated from Stemona cf. pierrei [76]. It became apparent that the stilbenoids of Stemona genus can be characterized mainly by the C-methylation of aromatic rings and the formation of phenylbenzofurans. 

Three novel phenanthrenes have been isolated from the wetland plant Juncus acutus. The structures of the novel phenanthrenes were established as 2-hydroxy-l,6-dimethyl-5-vinyl-phenanthrene (320), 2,7-dimethoxy-l,6-dimethyl-5-vinylphenanthrene (321) and 2-hydroxy-6-hydroxymethyl-l-methyl-5-vinyl-phenanthrene (322) [164, 165]. In spite of the great number of 9,10-dihydrophenanthrenes, only quite a small number of phenanthrenes have been reported until now as constituents of Juncaceae. 

Three new dihydrophenanthrenes, stemanthrenes A-C (356-358), along with the above mentioned bibenzyls (133, 135, 136 and 138) were isolated and identified from the underground parts of Stemona cf. pierrei. The structures showed a common substitution pattern for aromatic ring A and characteristic C-methylations for ring B. The trivial name, racemosol, for ring B was redefined to stemanthrene D (359) due to its priority for another compound [76]. 

The report on the biosynthesis of 9,10-dihydrophenanthrene is rare. A biosynthetic pathway of 9,10-dihydrophenanthrene was proposed by Preisig-Mueller et al. Bibenzyls are bicyclic intermediates and require O-methylation as a prerequisite for their conversion into dihydro-phenanthrenes [377]. 

The alkaloid glaucine (225) has been prepared by reduction of the photocyclisation product (226) obtained from irradiation of (227). The light induced coupling proceeds in very low yield. However, the chemical efficiency of the reaction was improved by utilising (228) in which the bromine substituent directs the regiochemistry of a stilbene-dihydrophenanthrene cyclisation via the presumed intermediate (229). Elimination of HBr from this species yields the isolated product which on reduction also yields (225). Photocyclisation of analogues of (227) in which not all of the phenol groups are methylated has also been described. 

Dihydrophenanthrene synthesis. Evans et al. have reported a new route to dihydrophenanthrene derivatives based on the condensation of p-quinone mono-ketals (1) or monosilyl cyanohydrin derivatives (5, 721-722) with the enolate of methyl 3-(3,4,5-trimethoxyphenyl)propionate (2) to give p-quinol ketals (3). These undergo acid-catalyzed cyclization to dihydrophenanthrene derivatives (4). A typical example is formulated in equation (I). The choice of the Lewis acid catalyst is sometimes critical for the cyclization. In the case of the cyclization shown above, use of SnCL, CF3COOH and BF3 etherate resulted in much lower... 

Rycroft DS, Cole WJ, Aslam N, Lamont YM, Gabriel R (1999) Killamiensolide, Methyl Orsellinates and 9,10-Dihydrophenanthrenes from the Liverwort Plagio-chila killarniensis from Scotland and the Azores. Phytochemistry 50 1167... 

Also, the similar treatment of phenanthrene (la) gave A-substituted A-methyl-9-amino-9,10-dihydrophenanthrenes (lOp-r) (Scheme 6.33). Cyclization of lOp and lOr... 

An unusual Sn -type substitution has been noted in the palladium-catalysed reaction of benzyhc c bonates, such as (90), 3-methyl-9,10-dihydrophenanthrenes... 

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