9,10-Dihydrophenanthrenes

Under different conditions [PdfOAcj2, K2CO3, flu4NBr, NMP], the 1 3 coupling product 86 with 4-aryl-9,10-dihydrophenanthrene units was obtained. The product 86 was transformed into a variety of polycyclic aromatic compounds such as 87 and 88[83], The polycyclic heteroarene-annulated cyclopen-tadicnc 90 is prepared by the coupling of 3-iodopyridine and dicyclopentadiene (89), followed by retro-Diels Alder reaction on thermolysis[84]. 

Z-Stilbene also undergoes photocyclization to 4a,4b-dihydrophenanthrene via an electrocyclization. ... 

Fig. 13.11. A schematic drawing of the potential energy surfaces for the photochemical reactions of stilbene. Approximate branching ratios and quantum yields for the important processes are indicated. In this figure, the ground- and excited-state barrier heights are drawn to scale representing the best available values, as are the relative energies of the ground states of Z- and E -stilbene 4a,4b-dihydrophenanthrene (DHP). [Reproduced from R. J. Sension, S. T. Repinec, A. Z. Szarka, and R. M. Hochstrasser, J. Chem. Phys. 98 6291 (1993) by permission of the American Institute of Physics.]...

A cleavage reaction reminiscent of that already noted with chloranil " has been observed at room temperature with DDQ. This reaction is remarkable in that it stops at the dihydrophenanthrene stage (78, 79) and takes place... 

To optimize selectivity, a wide array of diamine backbones were surveyed (Fig. 3.21). However, it appears that 1,2-cyclohexanediamine is unique in its catalytic properties. Only the closely related dihydrophenanthrene ligand 124 could... 

However, this oxidation to carbonyl failed with the complexes of tetralin, o-chlorotoluene, 9,10-dihydrophenanthrene, and acenaphthalene [109]. The aniline complex can be oxidized to the nitrobenzene complex using H202 in CF3C02H [86] Eq. (38). This reaction parallels the analogous oxidation of aminocobaltici-nium [86, 111],... 

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. 

Recent work identifying Plagiochila retrorsa Gottsche from collections made in the Azores and Madeira establishes a significant range extension for a taxon, known under several other names, which occurs in the southern Appalachian Mountains and in Costa Rica. Rycroft et al. (2001) described morphological and phytochemical characteristics of representative specimens of this liverwort. Phytochemically, P. retrorsa belongs to the 9,10-dihydrophenanthrene chemotype species (major stmctural type is that of compounds 449 and 450). 

The equilibrium concentration of dihydrophenanthrene under oxygen-free conditions is very small. However, this reaction, in the presence of Oa and I3, has been developed to the point where it is a good method for ring formation. 

The direct photolysis of cis- or ftmr-stilbene in solution gives rise to photo-isomerization. In addition, dihydrophenanthrene is formed from the cis isomer ... 

The value of the pss calculated from Eq. (9.24) is 2.74 and the measured value<7> is 2.64. While this agreement could be taken as evidence in favor of a triplet mechanism, it could also mean that the twist singlet and twist triplet have similar geometries (see Figure 9.2), and therefore similar decay ratios. In this mechanism we have neglected fluorescence from fraws-stilbene and dihydrophenanthrene formation from cw-stilbene. (See Problem 4.)... 

The reactions of tetrafluorobenzyne with 9,10-dihydrophenanthrene and phenanthrene yield the expected adducts formed by cyclo-addition at the 1,4-positions 90). The reaction of tetrafluorobenzyne with 1,6-methanocyclodecapentaene (52) was carried out in order to study the mass spectral and thermal fragmentation of (53) 90>. In the event benzocyclopropene and 1,2,3,4-tetrafluoronaphthalene (54) were formed. 

A small amount of 9,10-dihydrophenanthrene is observed (signal at 29.0 ppm) presumably as a result of rapid... 

Tetrahydro- and dihydrophenanthrenes have been formed (signals at 25.7 and 29. 0 ppm). 

The photochemical isomerization of E-stilbenes has been applied in the preparation of phenanthrenes, as Z-stilbenes undergo electrocyclie ring closure (cf. chapter 3.1.3) to dihydrophenanthrenes which in turn are easily oxidized to phenanthrenes (3.1) 305). This sequence has also been employed in the synthesis of benzoquinolines 306) or of benzoquinolizines (3.2) 307). 

The most famous of these compounds is combretastatin A-4 (CA-4,7), isolated by Pettit et al. in 1989 [30]. Pettit s research led to the isolation and structural determination of a series of phenanthrenes, dihydrophenanthrene, stilbene, and bibenzyl compounds [31]. CA-4 (7), alongside CA-1 (8), was found to be an extremely active inhibitor of tubulin polymerization [30,32]. The major problems associated with these compounds were poor bioavailability and low aqueous solubility [33,34], and hence, research in the field was turned to designing better alternatives with the hope of eradicating the negative properties of these potent compounds. 

When stilboestrol (diethylstilbestrol, 62) was photolysed in aqueous methanol at 254 nm it gave the stable 4a,4b-dihydrophenanthrene dione (63). The mechanism required a photo trans-cis isomerization, photocyclization and spontaneous enol-keto tautomerism [53,54]. Previous workers had carried out a similar irradiation in dilute acetic acid and obtained the expected aromatic product (64) [55],... 

The conjugated diene dienoestrol (65) was irradiated at 254 nm in 90% aqueous methanol. Rotation and cis-trans photoisomerization gave (66) which underwent a photochemical [1, 5]sigmatropic rearrangement to give (67). Photocyclization followed by enol-keto tautomerism then gave the isolated dihydrophenanthrene dione (68) [56]. 

Synthese von 2,4-Dimethoxy-6-hydroxy-9,10-dihydrophenanthren, by E. Hardegger, N. Rigassi, J. Seres, C. Egli, P. Muller, and K. O. Fitzi (29. Mitteilung, Welkstoffe und Antibiotika), Helv. Chim. Acta, 46 (1963) 2543-2551. 

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