1,3-Cyclopentadiene reaction with hydrogen

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... 

The easily proceeding interaction with water, alcohols and acids leads to the abstraction of cyclopentadiene and the formation of corresponding LnX3 compounds [11,17,91]. The reaction with hydrogen cyanide conducting under mild conditions (10-15°C) allows to obtain dicyclopentadienylcyanide complexes [133] ... 

Subsbtuting vinylic hydrogen in a,P-unsaturated carbonyl compounds with vinylic fluonne does not affect their dienophilic character negatively Indeed, 3,3-difluoroacrylic acid is more reactive toward furan than its nonfluonnated counterpart [95] (equation 81) Consistent with this observation is the fact that tctrafluorobenzoquinone forms only a bis-Diels-Alder adduct m 68% yield in its reaction with cyclopentadiene at room temperature [96, 97 ... 

Crystallization to obtain the major diastereomer in pure form is possible in some cases. These hydrogen-bonded vinylic sulfoxides undergo asymmetric 2 + 4-cycloaddition reactions with 1,3-cyclopentadiene (see p. 845). 

Ethylene carbonate, reaction with potassium thiocyanate, 42, 59 Ethylene sulfide, 42, S9 Ethyl formate, reaction with cyclo-hexylamine, 41, 14 Ethyl- -hexylamine, 43, 47 5-(2-Ethylhexyl)-l,2,3,4,5-pentachloro-cyclopentadiene, 43, 93 Ethylhydrazinium hydrogen oxalate,... 

The preparation of highly functionalized cyclopentadiene derivatives may by achieved by using oxalenes or their pyrylium salts (90 and 92, respectively), (see Scheme 14, where X = O). In this way, azalenes 26,51 29,8Z 88 32,51 or 3651 can be obtained by heating salts (90) with primary amines in dimethyl-formamide (Eq. 6). The reaction with sodium hydrogen sulfide gives thialenes... 

This reaction is quite clean-cut, and at least 95 percent of the products are accounted for by Eq. (28). Vanas and Walters " have studied the reaction in the gas phase and find that p" p° is about 1.9, which indicates the occurrence of some side reactions. However, they carried out a careful chemical analysis of the products and showed that the partial pressures of cyclopentadiene and hydrogen are equal to each other and to the increase in total pressure p p° over at least the first half of the reaction. With the exception of the last stages of the decomposition, this reaction is very well suited to the pressure method. In addition it has been shown that the reaction is homogeneous and does not involve a chain mechanism. 

Cyclopenteaediol isomers have previously been prepared by hydrolysis of acetates produced by reaction of dibromocyclopen-tene with potassiiun acetate in acetic acid by reaction of cyclo-pentene with selenium dioxide in acetic anhydride or by reaction of cyclopentadiene with phenyl iodosoacetate/ with lead tetraacetate, or with peracetic acid in the absence of base. Preparation of cydopentenediol without intermediate formation of acetates has been accomplished by reaction of cyclopentadiene with hydrogen peroxide in the presence of osmium tetroxide in terf-butanol, and hy reaction of cyclopentadiene with peracetic acid in a methylene chloride suspension of anhydrous sodium carbonate, followed by hydrolysis of the resulting epoxycyclo-pentene. ... 

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