Arylation cyclopentadiene

An alternative synthesis of a thermally stable cyclopentadienyl functionalized polymer involved ring bromination of poly(oxy-2,6-diphenyl-l,4-phenylene), followed by lithiation with butyl lithium to produce an aryllithium polymer. Arylation of 2-norbornen-7-one with the metalated polymer yielded the corresponding 2-norbornen-7-ol derivative. Conversion of the 7-ol to 7-chloro followed by treatment with butyl lithium generated the benzyl anion which undergoes a retro Diels-Alder reaction with the evolution of ethylene to produce the desired aryl cyclopentadiene polymer, 6. 

Arylated cyclopentadienes, especially pentaarylcyclopentadienes 6, have interesting properties as ligands for transition metals [1] or as electroluminescent materials [2], The classical methods for their preparation are multistep procedures [3], which are somewhat tedious and usually less suitable for sterically demanding aryl groups. In contrast, the palladium-catalyzed arylation of either metallocenes such as zirconocene dichloride (1) or simply cyclopentadiene (3) with aryl halides leads to the target compounds 4—6 in a single preparative step (Scheme 1) [4—6]. 

Note that the products are useful building blocks for the construction of certain functional systems including electroluminescent devices [81, 82]. The arylation proceeds via partially arylated cyclopentadienes in a stepwise manner. Thus, by the reaction of di- and triarylated cyclopentadienes, the corresponding... 

Organometallic Compounds The most widely used compounds [Is,2m] are the titanocene derivatives (10.36), which exhibit an excellent absorption around 500 nm and very efficiently eliminate an aryl and a cyclopentadienyl ligand yielding an unsaturated titanium species and an arylated cyclopentadiene. The Ti structure adds to the CO group of one acrylate unit (may be two) and generates the initiating radicals. Other systems include metal carbonyl (Mn, Fe, Mo, Cr, Os, Re, Ru, etc. [75,76]). 

The present synthesis10 consists of two simple steps, uses readily available and inexpensive starting materials, and produces pure material in high overall yield. It is based on two observations that nonenolizable ketones may be cleaved to carboxylic acids by potassium ferf-butoxide-water,2 and that aryl 2 chlorophenyl ketones may be cleaved with loss of the 2-chlorophenyl group to give only one of the two possible acids.11 Other compounds prepared by this route include carboxycyclopentadienyltriearbonylmanganese [Manganese, tricar-bonyl[(l, 2,3,4,5- )-l-carboxy-2,4-cyclopentadien-l-yl]-] (79%)10 and... 

Yasuda S, Yorimitsu H, Oshima K (2008) Synthesis of aryliron complexes by palladium-catalyzed transmetalation between [CpFe(CO)2l] and aryl Grignard reagents and their chemistry directed toward organic synthesis. Organometallics 27 4025 027 Jonas K, Schieferstein L (1979) Simple route to Li- or Zn-metalated r -cyclopentadien-yliron-olefin complexes. Angew Chem Int Ed Engl 18 549-550... 

Stable aryl boronates derived from tartaric acid catalyze the reaction of cyclo-pentadiene with vinyl aldehyde with high selectivity. Chiral acyloxy borane (CAB), derived from tartaric acid, has proved to be a very powerful catalyst for the enantioselective Diels-Alder reaction and hetero Diels-Alder reaction. Scheme 5 23 presents an example of a CAB 73 (R = H) catalyzed Diels-Alder reaction of a-bromo-a,/i-cnal 74 with cyclopentadiene. The reaction product is another important intermediate for prostaglandin synthesis. In the presence of... 

The second part of the theory, which is a logical consequence of the first, is that monomers that have more than one basic site, e.g., an aromatic ring or an oxygen atom, can form more than one type of complex with the carbenium ion this idea was first proposed by Plesch (1990) in the context of chemically initiated polymerizations. It helps to explain why aryl alkenes and alkyl vinyl ethers polymerize more slowly than isobutene and cyclopentadiene. The reason is that all the complexes formed by the alkyl alkenes are propagators, whereas for the aryl alkenes and vinyl ethers only a fraction of the population of complexes can propagate. 

The normal [4 + 2] cycloadditions are most frequently observed and generally proceed more easily than the other reaction types. Recently, Sauer and colleagues48 demonstrated that each of these three types of Diels-Alder reactions can be observed in the cycloadditions of a series of polyhalogenated cyclopentadienes with aryl substituted dienophiles, the actual reaction type observed depending on the substitution pattern of the reactants. 

Aryl(dialkylamino)carbene chromium complexes do not yield aminonaphthols upon treatment with alkynes, but form indene derivatives. Vinyl(dialkylamino)car-bene complexes, however, react with alkynes to yield aminophenols as the main products if solvents of low nucleophilicity are used [335]. (2-Amino-1-vinyl)carbene complexes do not undergo benzannulation when treated with alkynes, but form cyclopentadienes or heterocycles instead [251]. 

The flash vacuum pyrolysis of alkynes, arynes, and aryl radicals has been reviewed. A discussion of secondary reactions and rearrangements is included. The pyrolysis of cyclopentadienes has also been examined. The rates for the initial C—H bond fission and the decomposition of C-C5H5 have been calculated. A single-pulse shock study on the thermal decomposition of 1-pentyl radicals found alkene products that are formed by radical isomerization through 1,4- and 1,3-hydrogen migration to form 2- and 3-pentyl radicals. The pyrrolysis of f-butylbenzene in supercritical water was the subject of a report. ... 

An unexpected and potentially useful mode of reactivity was observed in the reaction of cinnamaldehyde and cyclopentadiene catalysed by diarylprolinol silyl ether 39 [73]. Rather than observing a Diels-Alder adduct, the products resulting from an ene reaction were isolated in excellent yield. The transformation was found to be general for a series of P-aryl acroleins (40) with routinely excellent levels of... 

A versatile new and general method was developed for the synthesis of six-membered 1,3-heterocycles. In comparison with the general reaction conditions of retrodiene reactions, a very mild retro Diels-Alder (RDA) decomposition was found to occur when the norbornene-d/eAro- or -diendo-fused dihydrooxazinone 474 was heated at melting temperature or refluxed in different solvents (e.g., chlorobenzene). Cyclopentadiene splitt off and the 2-aryl-6//-l,3-oxazin-6-ones 475, earlier unknown representatives of the simple 1,3-oxazines, were obtained (84S345, 84T2385). 

Cyclopentadienes, 1,3-cyclohexadienes, 1,3-cycloheptadienes, as well as furan and aklyl-substituted furans, have been investigated as substrates of photosensitized oxygenation reactions, while aromatic compounds such as anthracenes and tetracenes as well as aryl-substituted carbo-and heterocyclic pentadienes were studied in direct and indirect (photosensitized) photooxygenation reactions. 

Pentaarylcyclopentadienols (375) are reported to yield endoperoxides (376) which when heated or treated with acids decompose to tetraarylfurans and the corresponding aryl acids.251 Tetraarylsubstituted cyclopentadienones such as tetracyclone (378) lead to m-diaroylstil-benes and carbon monoxide.252-255 Probably, as with other cyclopentadienes, endoperoxides are the primary products. However, no attempts seem to have been made to elucidate the mechanisms of rearrangements and decompositions involved in these reactions. 

Aryl-lithium-Verbindungen und Aryl-magnesiumhalogenide konnen in einer quasi-kata-lytischen Reaktion in Amino-arene ubergefuhrt werden, indem man sie zunachst mit 0-(4-Methyl-benzolsulfonyl)-N-(tetraphenyl-cyclopentadienyliden)-hydroxylamin umsetzt und das so erhaltene Arylimino-tetraphenyl-cyclopentadien mit Hydroxylamin in Pyridin zum gewunschten Amino-aren und dem wieder verwendbaren Hydroximino-te-traphenyl-cyclopentadien spaltet3 ... 

Unexpectedly, Grieco discovered that immonium ions derived from aryl amines and aldehydes do not function as heterodienophiles toward cyclopentadiene, as was found in the case of simple immonium ions, but rather they acted as 2-azadienes leading to a novel synthesis of tetrahy-droquinolines (88TL5855). 

The reaction of a with cyclopentadiene also can follow two paths [3 + 4]- or [2 + 4]cycloaddition. The former is seen when R is alkyl, the latter when R is aryl (equation II).2... 

As with the alkyl and aryl derivatives of the pyrrolenines and indolenines, a tautomeric equilibrium has also been noted between the pentachloro-2//- and -3H- pyrroles, such that when the 2//-pyrrole, produced by chlorination of 2,3,4,5-tetrachloropyrrole or of 3,4-dichloromaleimide, is allowed to react with dienophiles, the adducts are those formed by cycloaddition with the 3H-pyrrole tautomer (Scheme 84) (80JOC435, 80JA7862, 81JOC3036). Cycloaddition with cyclopentadiene occurs on the 2H-pyrrole, which behaves as the dienophile. 

A large number of metal-coordinated chalcogenacycles were prepared from the heteroaldehyde and -ketone complexes [M(CO)5 E=C(Ph)R ] (M = Cr, Mo, W E = S, Se, Te R = H, Aryl) and 1,3-dienes. The cycloadditions proceeded rapidly, even at low temperatures.179180,228-233 As dienes 2,3-dimethyl-l,3-butadiene [for an example see Eq. (27)], isoprene, transA, 3-pentadiene, cyclopentadiene, pentamethylcyclopentadiene, and 1,3-cyclohexadiene were used. Decomplexation with pyridine/THF yielded the free heterocycles. Although the tellurobenzaldehyde complex [W(CO)5 Te = C(Ph)H ] (99c) proved too unstable for isolation, it could be generated and employed in subsequent cycloadditions with dienes.180... 

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