Reaction of atomic oxygen with cyclopentadiene

The reaction of 1,3-cyclopentadiene (CPD) with ground-state atomic oxygen O(³P), produced by mercury photosensitized decomposition of nitrous oxide, was studied. The identified products were carbon monoxide and the following C₄H₆ isomers: 3-methylcyclopropene, 1,3-butadiene, 1,2-butadiene, and 1-butyne. The yield of carbon monoxide over oxygen atoms produced (?_CO) was equal to the sum of the yields of C₄H₆ isomers in any experiment. ?_CO was 0.43 at the total pressure of 6.5 torr and 0.20 at 500 torr. We did not succeed in detecting any addition products such as C₅H₆O isomers. It was found that 3-methylcyclopropene was produced with excess energy and was partly isomerized to other C₄H₆ isomers, especially to 1-butyne. The excess energy was estimated to be about 50 kcal/mol. The rate coefficient of the reaction was obtained relative to those for the reactions of atomic oxygen with trans-2-butene and 1-butene. The ratios k_CPD+O/k_{trans-2-butene+O}= 2.34 and k_CPD+O/k_1-butene+O = 11.3 were obtained. Probable reaction mechanisms and intermediates are suggested.     

Reaction of aluminacyclopentadienes with aldehydes affording cyclopentadiene derivatives

Aluminacyclopentadienes, prepared in situ from the reaction of AlCl₃ and 1,4-dilithio-1,3-dienes at room temperature, reacted with aldehydes at room temperature to afford cyclopentadiene derivatives including tetrahydroindenes in good to excellent yields. Both aromatic and aliphatic aldehydes undergo this reaction.     

三(三甲基硅)环戊二烯与六羰基钼的反应

三(三甲基硅)环戊二烯与六羰基钼在二甲苯中回流8h,反应停留在生成中间物η⁵-[(Me₃Si)_NC₅H_5-n]Mo(CO)₃H(n=2,3)(I)的阶段.不经分离,I随即分别与CCl₄·NBS及MeI反应,生成其相应的钼卤化物η-⁵[(Me₃Si)_NC₅H_5-n]Mo(CO)₃X[n=3,X=Cl(1),Br(2),I(3);n=2,X=Cl(4),Br(5),I(6)].4-6是由于茂环上脱掉1个Me₃Si基.经元素分析和IR及¹H NMR谱表征了化合物1-6的结构,并用X射线衍射测定了1的晶体结构.     

Reaction of quinoid derivatives of 4,4a-Dihydropyrido[1,2-a]-3H-benzimidazole with cyclopentadiene

Diels-Alder reaction between quinone mono-, diimines, and methylenequinone imines of 4,4a-dihydropyrido[1,2-a]-3H-benzimidazole series and cyclopentadiene proceeds endo-stereoselectively at the unsubstituted π-bond of the quinoid ring affording a mixture of diastereomeric cycloaddition adducts.     

Reaction of fluorochlorocarbene with cyclopentadiene,indene, and their alkyl derivatives by phase transfer catalysis

Fluorohalocarbene, generated from CHCl₂F using phase transfer catalysis, reacts with indene, cyclopentadiene, and their alkyl derivatives to form 2-fluoronaphthalenes or fluorobenzenes in 9–60% yield. Reactions proceed through formation of unstable fluorochlorocyclopropanes, which rearrange selectively independently of their stereochemical configuration into the corresponding aromatic fluorides with elimination of HCl.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1609–1613, July, 1990.     

Kinetic study of reaction of difluorocarbene with cyclopentadiene

Russian Chemical Bulletin -     

Reactions of heteroaromatic thiols with 1,3-butadiene and cyclopentadiene

The formation of 1,2 and 1,4 adducts in the reaction of 5-chloro-2-thiophenethiol, 2-benzofuranthiol, 2-benzothiophenethiol, and 3-methyl-2-benzothiophenethiol with conjugated dienes in the presence of various amounts of ethylsulfuric acid and also without a catalyst was studied. Catalytic acceleration of the reaction with ethylsulfuric acid indicates the heterolytic character of the addition.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1335–1337, October, 1982.     

Cyclocondensation of lower aliphatic aldehydes with arylamines and cyclopentadiene

Three-component condensation of lower aliphatic aldehydes (C₁-C₃) with arylamines and cyclopentadiene (the Povarov reaction) gave 3a,4,5,9b-tetrahydro-3H-cyclopenta[c]-quinolines. Ozonization of their N-trifluoroacetyl derivatives afforded the corresponding ozonides. Cyclocondensation of 4-fluoroaniline with formaldehyde and cyclopentadiene gave earlier unknown 2-fluoro-3b,6,6a,7,9,9a,10,12a-octahydrobenzo[i,j]dicyclopenta[b,g]quinolizine.     

On the reaction of hexafluoropropene with butadiene and cyclopentadiene

Reaction of hexafluoropropene with butadiene and cyclopentadiene in a stationary system was studied. The reaction of hexafluoropropene with burtadiene was shown to proceed along the scheme of [2+2]-cycloaddition, and with cyclopentadiene, as [2+4]-cycloaddition.     

Reversible and regioselective reaction of La@C82 with cyclopentadiene

The reversible and regioselective reaction of La@C82 with cyclopentadiene was carried out. The activation and thermodynamic parameter of the retro-reaction was estimated from the Arrhenius plots of the rate constants.     

Anharmonic thermochemistry of cyclopentadiene derivatives

This paper focuses on the thermochemistry of some derivatives of cyclopenta‐1,3‐diene, namely, 5‐methylcyclopenta‐1,3‐diene, 5‐ethylcyclopenta‐1,3‐diene, 5‐formylcyclopenta‐1,3‐diene, 5‐methylcyclopenta‐1,3‐diene‐1‐yl radical, 5‐ethylcyclopenta‐1,3‐diene‐1‐yl radical, 5‐carbonylcyclopenta‐1,3‐diene radical, 1‐formylcyclopenta‐2,4‐diene‐1‐yl radical, 5‐methylenecyclopenta‐1,3‐diene radical, 5‐ethylidenecyclopenta‐1,3‐diene radical, and 3,6‐dimethylenecyclohexa‐1,4‐diene. Several different chemistries of these compounds are of interest in combustion modeling. Here, we present gas‐phase thermochemical properties for the above cited species, which are, except for 3,6‐dimethylenecyclohexa‐1,4‐diene, previously unknown. These were obtained from corrected (using bond additivity corrections) high‐level ab initio quantum chemistry calculations validated with well‐known compounds including cyclopentane, cyclopentene, cyclopenta‐1,3‐diene, and cyclopentadienyl radical. Heat capacities and entropies have been corrected for anharmonic molecular motions, in particular for internal rotations. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 453–463, 2003     

Preparation of cyclopentene from cyclopentadiene

Summary A convenient laboratory method is proposed for the preparation of cyclopentene by the hydrogenation of cyclopentadiene. Yields of up to 70% are obtained.     

AlPO-Catalysed asymmetric Diels-Alder reactions of cyclopentadiene with chiral acrylates

Reactions of cyclopentadiene with several chiral acrylates are studied and compared with the same reactions catalysed by Zn(II)-exchanged K10 montmorillonite. In general, amorphous AlPO₄ is a more efficient catalyst than the clay. In particular, the reaction of cyclopentadiene with (−)-8-phenylmenthyl acrylate leads to 74% diastereomeric excess (d.e.) in methylene chloride at low temperatures. This result constitutes the highest asymmetric induction described to date for a solid-catalysed asymmetric Diels-Alder reaction. When the reactions are carried out in the absence of a solvent a noticeable decrease in selectivity is observed, probably due to an extensive competition of the non-catalysed reaction.     

Synthesis and Diels-Alder reactions of homochiral 2-sulfinylmaleates with cyclopentadiene

Enantiomerically pure 2-p-tolylsulfinylmaleates 1, 2 and 3 have been readily prepared by Knoevenagel reaction between (S)-menthyl p-toluenesulfinate and glyoxylic acid. Their asymmetric Diels-Alder reactions with cyclopentadiene have been studied under a wide range of uncatalyzed and catalyzed conditions and the stereochemical results have been explained by assuming a steric control approach, in term of S-cis or S-trans favoured conformations. Uncatalyzed Diels-Alder reactions of 1 and some Lewis acid catalyzed Diels-Alder reactions of 2 show high facial and endo selectivities. The facial selectivity of dienophile 2 highly depends on the Lewis acid, whereas reactivity of 1 and 3 is very sensitive to the solvent. These sulfinylmaleates 1, 2 and 3 act as synthetic equivalents of chiral acetylenedicarboxylates in Diels-Alder reactions after basic elimination of the sulfinylic moiety in the resulting adducts.