Phenanthrenes, Diels-Alder reaction

Dihydrovinylphenanthrenes are more reactive than the corresponding vinyl phenanthrenes and undergo Diels-Alder reactions easily. They have been used in the synthesis of polycyclic aromatic compounds and helicenes. Examples of cycloaddition reactions of the 3,4-dihydro-1-vinylphenanthrene (70), [61] 3,4-dihydro-2-vinylphenanthrene (71) [68] and l,2-dihydro-4-vinylphenanthrene (72) [69] are reported in Equation 2.22 and Schemes 2.27 and 2.28. 

The partially hydrogenated phenanthrene derivative 18 (entry 4) is a very moderate diene due to the steric crowding caused by the substituents and the anulated rings, and it reacts even with highly reactive dienophiles such as maleic anhydride (MA) or N-phenylmaleic imide only at high pressure. The minor product 20 in the reaction with MA obviously stems from diene 21. This can be explained by a double-bond isomerization 18 - 21 prior to the cycloaddition, certainly catalyzed by traces of acid present in the MA. In the absence of acid only the Diels-Alder adduct 22 derived from diene 18 was observed. In the reaction of diene 23 with MA (entry 5) a similar sequence of steps was observed. A [1,5] shift of the C—O bond in 23, again certainly acid-catalyzed, produces the diene 26 followed by the Diels-Alder reaction with MA to give 24 and 25. 

A review of Diels-Alder reactions of fullerenes with acyclic and cyclic dienes has been presented. The addition of substituted pyrimidine o-quinodimethanes (75) to [60]fullerenes yields novel organofullerenes (76) bearing a pyrimidine nucleus covalently attached to the Ceo cage (Scheme 26). The Diels-Alder dimerization of cyclopenta[/]phenanthrene (77) with isobenzindene (78) yields the dimer (79) in 85% yield (Scheme 27). Further evidence has been supplied to support an early reorganization of the r-network in the dimerization of 2-methoxycarbonylbuta-1,3-diene. The Lewis acid-catalysed Diels-Alder reactions of acrylate derivatives of new carbohydrate-based chiral auxiliaries with cyclohexadiene show excellent endo. exo... 

Aromatic compounds can also behave as dienes.858 Benzene is very unreactive toward dienophiles very few dienophiles (one of them is benzyne) have been reported to give Diels-Alder adducts with it.859 Naphthalene and phenanthrene are also quite resistant, though naphthalene has given Diels-Alder addition at high pressures.860 However, anthracene and other compounds with at least three linear benzene rings give Diels-Alder reactions readily. The interesting compound triptycene can be prepared by a Diels-Alder reaction between benzyne and anthracene 861... 

A route to partially hydrogenated phenanthrenes relies on the Diels-Alder reaction of a benzyne to an annulated furan, e.g. (501) - (503) (Scheme 117). However, regiochemistry raises its ugly head when both the furan and the benzyne are nonsymmetrically substituted (Scheme 118). Hence, the [4 + 2] cycloaddition of 3-methylbenzyne with 2>substituted furans (504) gave the anti and syn adducts (506)... 

Formation by a concerted cycloaddition reaction A phenantlirene tnolecuie would be formed in two ways as below tlie [4 + 2] cycloaddition of biphenyl with two benzene molecules followed by a retro Diels-Alder reaction and by dehydrogenation the 14 + 2] cycloaddition of naphthalene witli benzene followed by the retro Diels-Alder reaction and dehydrogenation. An anthracene molecule would be formed by the [4 + 2] cycloaddition of naphtlialene with benzene followed by retro Diels-Alder reaction and by dehydrogenation. In these cases, tlie yield relation would be phenanthrene anthracene, because biphenyl is produced more abundantly than is naphtlialene during shock reaction. This statistical consideration fits the experimental results. 

These PAHs could be arranged so that a series of successive two- and four-carbon additions would result in all these species being produced through a buildup of rings. The additions are not random, but are determined by two simple structural features. If a PAH had a three-sided bay (concave) region (such as phenanthrene or benzo[e]pyrene), a two carbon addition closed that area (e.g., going from phenanthrene to pyrene). This is conceptually similar to a Diels-Alder reaction. 

Another approach to hydrophenanthrenones and mono- and di-substituted phenanthrenes, based on Diels-Alder reaction between Danishefsky diene (13) and 1-nitronaphthalene (14), has been developed by Mancini et When 1-nitronaphthalene (14) interacts with the electron-rich diene 13 under high pressure, the cycloaddition occurs at a lower temperature and, after aromatization, allows 2-hydroxyphenanthrene (15) to be prepared (Scheme 7.4). 

A route to partially hydrogenated phenanthrenes relies on the Diels-Alder reaction of a benzyne to an annulated furan, e.g. (501) (503) (Scheme 117). However, regiochemistry raises its ugly head ... 

Figure 39 presents the characteristic three phases of PVC decomposition very clearly. The initial dehydrochlorination reactions form FIC1 and polyene structures. During this phase, benzene and some naphthalene and phenanthrene are also formed through Diels-Alder reactions and the successive dealkylation of polyene molecules. Then, when Cl has been quantitatively released... 

In this original and imaginitive approach, a rapid assembly of the phenanthrene core of morphine, containing a novel non-aromatic A ring, was achieved in an intermolecular Diels-Alder reaction between quinone 173 (prepared from 3-methoxy-2-hydroxy benzaldehyde in 7 steps and an overall yield of 35%) and diene 174 (from 1,4-cyclohexanedione monoethylene ketal in 2 steps with an overall yield of 30%), Scheme 20. In one of several unsuccesful attempts to aromatize ring A, an unexpected tandem... 

Tables. Enmtioselective Diels-Alder Reactions of Diene 139 with Dienophiles of Type 140 Mediated by Ti-TADDOLate Complexes, Formed by Reactions of TADDOL AX (Scheme 67 R = phenanthrene-9-yl) with (i-Pr)2TtCl2 [130d]...

In 2014 several reports described the use of inverse-electron-demand Diels-Alder reactions to furnish naphthalene-based compounds from phthalazine-containing ring systems. Employing nonprecious metal complexes, copper(l) and nickel(O) complexes, instead of silver salts to catalyze formal [4+ 2] cycloadditions of 1,2-diazines and siloxyalkynes, Rawal and his group developed an environmentally friendlier and more economical method for preparing siloxy derivatives of naphthalene, anthracene, and phenanthrene (Scheme 16) (140L3236). In addition, the copper catalyst could also be employed for the synthesis of the corresponding quinolines and isoquinolines. This method provided the respective products in... 

With an efficient synthetic protocol to synthesize polysubstituted ot-pyrones, including chromen-2-one, from MBH adduct in hand, various substituted a-pyrones 132 have been subjected to reaction with dimethyl acetylenedi-carboxylate (DMAD) to obtain aromatic compounds 133 in excellent yields via Diels-Alder reaction (Scheme 4.37).Naphthalenes and phenanthrenes could be further obtained from some of the aromatic compounds by DDQ oxidation. 

Overcrowded 4,5-bis(2-pyridyl)phenanthrenes 28a and 28b were prepared from the Diels-Alder reactions between 4a,5a-diazoniapentaphene diperchlorate (26) and ketene acetals 27a and 27b, respectively (Scheme 5) [16]. The X-ray structure... 

Diels-Alder reactions, 133, 135 epoxidation, 69-72, 516 grafting on polyethylene, 462 hydroformylation, 44 hydrogenation, 41, 42 isomerization catalysts, 133, 484 isomerization during polymerizations, 484 isomerization kinetics, 484 isopropyl alcohol radical reaction, 207 MA copolymerization, 532, 534, 541 Michael reactions, 63-66 nitrone adducts, 224, 225 olefin copolymerization, 288 olefin ene reactions, 162 phenanthrene adducts, 181 plasticizers use, 14 production—synthesis, 14, 78-81 radical copolymerization, 270, 275-277, 307, 315, 317, 333, 345, 365, 379 radical polymerization, 239, 264, 287 reaction with allyl alcohol, 46 reaction with sodium bisulfite, 53 styrene copolymerization, 365, 483 tetraalkyl methylenediphosphonate adduct, 66 transesterification, 46 /7-xylylene copolymerization, 359 dialkyl stannyl, PVC stabilizer, 275 diaryl, synthesis from MA, 80 pyridinium, betaine intermediate, 216... 

The higher reaction temperature is required in the imino Diels-Alder reaction leading to cryptopleurine, relative to julandine, since lower reaction temperatures give rise to numerous uncharacterized by-products. This is not surprising since effecting the [4+2] cycloaddition to produce cryptopleurine involves disruption of the aromatic phenanthrene unit followed by isomerization in situ to regain aromaticity. 

THF at room temperature to produce substituted phenylallenes (231). Various arynes and terminal and internal alkynes can be used. The reaction of alkyne without propar-gylic hydrogen gave an acetylenic C-H addition product (a phenylalkyne) and a dehydro-Diels-Alder product (a phenanthrene).266... 

Other workers also have applied the Diels-Alder addition reaction to the preparation of angular-substituted derivatives of phenanthrene possibly obtainable as products of degradation of the morphine alkaloids. 

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