Cyclopentadiene 1-chloro

C4,H3oCl5lrN2P2 C7H8, Bis(triphenylphosphine)-(tetrachlorodiazo-cyclopentadiene)-chloro-iridium(l) toluene solvate, 46B, 1132 C41H37BFeN203, Benzimidazoledicarbonyl-TT-cyclopentadienyliron tetra-phenylborate acetone, 43B, 1093... 

Tropone (125) and the 2-substituted tropones showed a different reactivity in the cycloaddition with 2-cyclopentenone (28). Whereas tropone itself (125) and the 2-methoxytropone (126) reacted at lOkbar, giving a mixture of four and three products, respectively (Scheme 5.18), 2-hydroxy- and 2-chloro-tropone failed to react at all [43b]. Compound 127 does not have the expected dihydro-homobarrelenone framework it is probably derived from the cycloaddition of 125 and 1,4-cyclopentadien-l-ol, the enol form of 28. 

Inagaki, Fujimoto and Fukui demonstrated that ir-facial selectivity in the Diels-Alder reaction of 5-acetoxy- and 5-chloro-l,3-cyclopentadienes, 1 and 2, can be explained in terms of deformation of a frontier molecular orbital FMO [2], The orbital mixing rule was proposed to predict the nonequivalent orbital deformation due to asymmetric perturbation of the substituent orbital (Chapter Orbital Mixing Rules by Inagaki in this volume). 

The orbital mixing rule demonstrates that the direction of the FMO extension is controlled by the relative energies of the Jt-HOMO (ej and the n-orbital of X (8 ). In the case of 5-acetoxy- and 5-chloro-l,3-cyclopentadienes, the jt-HOMO lies higher than n (e > ej. In this case, the ji-HOMO mainly contributes to the HOMO of the whole molecule by an out-of-phase combination with the low-lying n. The mixing of a-orbital takes place so as to be out-of-phase with the mediated orbital n. The HOMO at Cl and C4 extends more and rotates inwardly at the syn face with... 

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. 

The dichlororuthenium arene dimers are conveniently prepared by refluxing ethanolic ruthenium trichloride in the appropriate cyclohexadiene [19]. The di-chloro(pentamethylcyclopentadienyl) rhodium dimer is prepared by refluxing Dewar benzene and rhodium trichloride, whilst the dichloro(pentamethylcyclo-pentadienyl)iridium dimer is prepared by reaction of the cyclopentadiene with iridium trichloride [20]. Alternatively, the complexes can be purchased from most precious-metal suppliers. It should be noted that these ruthenium, rhodium and iridium arenes are all fine, dusty, solids and are potential respiratory sensitizers. Hence, the materials should be handled with great care, especially when weighing or charging operations are being carried out. Appropriate protective clothing and air extraction facilities should be used at all times. 

Recently, Malpass et al. reported a synthesis of epibatidine isomers also under reductive Heck conditions [134, 135]. 2-Azabicyclo[2.2.1]heptene 167 was assembled by cycloaddition of an iminium salt with cyclopentadiene. Treatment of 167 with 2-chloro-5-iodopyridine provided a mixture of exo-5-(6-chloro-3-pyridyl) derivative 168 and exo-6-(6-chloro-3-pyridyl) derivative 169. 

Importantly, the development of the more reactive SbF6 catalysts foreshadowed the catalyzed cycloadditions of less reactive substrates. Diels-Alder reactions of 0-substituted acryloylimides could be efficiently induced with catalyst 271c often with improved selectivities. The most illustrative example is the chloro-substituted acryloylimide that provides <10% yield of cycloadduct with cyclopentadiene after 24 h at ambient temperature with catalyst 269c. When the SbF6 catalyst 271c is used, complete conversion is observed, to provide the cycloadduct with improved enantioselectivity and diastereoselectivity, Table El (199). 

Treatment of a mixture of a chloro oxime 177 (R = H, Ph, 4-BrCgH4 or 2-furyl) and a diene (cyclopentadiene or 2,3-dimethylbuta-l,3-diene) with solid sodium carbonate results in the formation of a dihydrooxazine, the intermediate nitrosoalkene 178 having reacted as a heterodiene (equation 98)94. In contrast, l,l-dichloro-2-nitrosoethene and cyclopentadiene yield the epoxyepimine 179 (equation 99)94. 

The ozonolysis reaction, followed by reductive workup with sulfur dioxide, as described in Part A of the present procedure, illustrates a general method which has been developed for the preparation of acetals. Application of the procedure is illustrated by conversion of the following olefins in alcoholic solution to the corresponding acetals (1) l-chloro-4-(o-nitrophenyl)-2-butene to o-nitrophenylacetaldehyde dimethyl acetal in 84% yield (2) l,4-dibromo-2-butene tobromoacetaldehyde dimethyl acetal in 67% yield (3) 3-butenoic acid to malonaldehydic acid diethyl acetal ethyl ester in 61% yield (4) cyclopentadiene to malonaldehyde bis(diethyl acetal) in 48% yield and (5)... 

Good results were also obtained in the Diels-Alder reactions of methyl 2-chloro-2-cyclopropylideneacetate (1-Me) with cycloalkadienes. Thus, 1-Me reacted with cyclopentadiene within 5 h at ambient temperature to give endo/exo-... 

This reaction should be carried out with undiluted cyclopentadiene if reasonably pure distilled 3-chlorocyclopentene is to be isolated. However, if a distilled product is not required, a solution of cyclopentadiene (Note 5) may be used. 3-Chloro-cyclopcntcne is somewhat more stable in solution. 

The only practical laboratory preparation of cyclopentadiene is by the depolymerization of dicyclopentadieneA M 3-Chloro-cyclopentene has been prepared by the addition of hydrogen chloride to cyclopentadiene.2 7 8 9 10... 

Cyclohexylmethylpropiolaldehyde diethyl acetal, 39, 60 1,2-Cyclononanedione, 36, 78 Cyclopentadiene, 32, 41 36, 32, 35 Cyclopentanecarboxylic acid, METHYL ESTER, 39, 37 Cyclopentanol, 2-chloro-, irans-,... 

Chloro-(i/4-cyclopentadien)-(penta-fluoro-phenvl)- ElOb,. 426 (Cl - C6F5)... 

Difluoro-5-phcnyl-1,2.3.4-tetra-chloro- V/3. 273 (5.5-F2 -Cl4-cyclopentadiene + Slyro )... 

Chloro-l, 3-butadiene, 71 Cyclopentadiene, 78 Cyclopropenone 1,3-propanediyl ketal,... 

PhCH=C(C4Cl4) = l,2,3,4-tetrachloro-6-phenylfulvene C5H2C14 = 1,2,3,4-tetra-chloro-1,3-cyclopentadiene. 

Although it has not been possible to isolate the diazacyclopentadienone (47), indirect evidence for its involvement in this reaction has been obtained by trapping experiments. When an ether solution of 3,4-diphenyl-4-chloro-2-pyrazolin-5-one was treated with triethylamine in the presence of cyclopentadiene, an excellent yield was obtained of compound (51), which has been shown to be the Diels-Alder adduct. The unlikely possibility that (47) could have the alternative structure in which (51) acts as diene rather than dienophile can be excluded on the basis of the appearance of normal hydrazide carbonyl absorption. 

Sensitized addition of cyclic dienes with chlorinated alkenes, employing an excess of the latter, yields mixtures of [4+2] and [2+2] adducts (Sch. 10). A substantial proportion of [4+2] adduct 46a is formed when cyclopentadiene 32 is the diene, but cyclohexadiene 36 yields almost entirely the [2+2] adduct 46b. Use of acyclic 1,3-dienes leads only to [2+2] products. The regioselectivity of the cycloadditions is consistent with a biradical intermediate 48 [47]. Sensitized irradiation of cyclopentadiene with 1-acetoxy acrylonitrile 49 also gives a [4+2] and [2+2] mixture, but with a higher proportion of the [4+2] adduct than the reactions using chloro-alkenes 45 [33-35]. 

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