1.3- Cyclopentadiene reactions

Photolysis of dicyclopentadienyltin results in formation of the Cp- radical (again detected by ESR), along with the precipitation of some unidentified yellow solid54. In contrast, photolysis of dicyclopentadienyllead produces no Cp-, unless di-f-butyl peroxide or biacetyl are added to the reaction mixture. The trimethylstannylcyclopentadienyl radical was produced by photolysis of bis(trimethylstannyl)cyclopentadiene (reaction 35), and was detected using ESR spectroscopy57. 

Cyclopentadiene reaction with HCN, 33 19, 20 vibrational spectra, 42 243 Cyclopentane... 

Pt-Sn Pt-Re Activities and selectives, A1203 support n-Hexane reforming, cyclopentadiene reactions. 

The reactions are very fast, and halide ion addition always leads to 77-allylpalladium halide dimers. The cyclopentadienyl moiety has been isolated in the form of cyclopentadiene (reaction with hydrogen chloride), or as a carboxylic acid dimer (reaction with BuLi -f CO2). That part of the attacking reagent bearing positive charge always combines with the C5H5... 

Thus photolysis of the tosylhydrazone sodium salt of 5//-dibenzo[a,c]cyclohepten-5-one (14) at — 60 °C in the presence of cyclopentadiene or furan with tetrahydrofuran as cosolvent gave the cyclopropene Diels-Alder adducts 17 and 18 in 73 and 47% yields, respectively. If the photolysis was stopped shortly after all the tosylhydrazone salt had decomposed, adduct 17 was the only isomer found in the cyclopentadiene reaction. In the formation of the furan adduct 18, the reaction was not so clean and a number of unidentified products were also formed. Unfortunately, adduct 18 is thermally unstable at the temperature necessary for thermal formation of carbene 15. No trace of adduct 18 was detected when the arylcarbene 19 was generated directly from its tosylhydrazone salt in the presence of furan. ... 

Table 1. Major Products Formed in Co Atom-Alkyne-Cyclopentadiene Reactions...

The reaction of vinylcaibenoids with all l-substituted acyclic dienes is an effective method for stereoselectively constructing highly functionalized cycloheptadienes. Unlike the cyclopentadiene reaction, rran -divinylcyclopropanes in addition to the [3+4] annulation products can be formed in some cases. For example, rhodium(II) acetate catalyzed decomposition of 4 in the presence of 4-methyl-l,3-pentadiene results in a 4 1 mixture of the [3+4] annulation product 17 and the tran -divinylcyclopropane 18 (Scheme 8). The regiochemistiy... 

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