Catalytic cycloaddition of diazoalkanes generated in situ to fullerene C60

Tuktarov, Airat R.; Korolev, V. V.; Джемилев, У. М.

doi:10.1134/s1070428010040251

Cited by 16 publications

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“…5 In continuation of these studies and also to examine the effect of alkyl substituent size in the original diazoalkanes upon the selectivity of the reaction, we have carried out catalytic cycloaddition between C 60 and diazoalkanes generated in situ by oxidation of hydrazones of butiric, valeric and caproic aldehydes. The above reaction was found to provide the formation of the corresponding homofullerenes 1-3 (Scheme 1), while the yield of target [5,6]-open adducts decreases slightly with increasing the alkyl chain length of diazoalkane. Scheme 1.…”

Section: Resultsmentioning

confidence: 99%

“…Apparently, the decrease in the selectivity of the reaction is conditioned by the presence of the second alkyl substituent at the bridging C atom of the cycloadduct raising the probability of the stereoisomeric [5,6]-open adduct formation.…”

Section: Resultsmentioning

confidence: 99%

“…In our view, the reaction of fullerenes with diazo compounds due to its great synthetic potential is regarded as a very promising method to synthesize methanofullerenes and also allows, together with the [6,6]-closed adducts, obtaining the [5,6]-open isomeric ones.…”

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confidence: 99%

“…It is accompanied by the formation of a mixture of [6,6]-closed (methanofullerenes) and stereoisomeric [5,6]-open (homofullerenes) adducts.…”

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confidence: 99%

“…Over the past 5-10 years, we have been actively engaged in research of the cycloaddition reaction between diazo compounds and [60]fullerene under catalytic conditions and found that among the tested complexes and salts of Cu, Pd and Rh a three-component catalytic system Pd(acac) 2 -PPh 3 -Et 3 Al has the greatest efficiency and selectivity in the reactions of C 60 with the simplest diazoalkanes, 5 diazoacetates, 6,7 and diazoketones 8 to promote the selective formation of the corresponding homo-or methanofullerenes. Herein, we attempted to explore the application boundaries of the cycloaddition reaction of diazo compounds to C 60 in the presence of Pd(acac) 2 -PPh 3 -Et 3 Al catalyst on the example of symmetric and asymmetric diazoalkanes and also higher diazoacetates of various structure.…”

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confidence: 99%

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Palladium-catalyzed selective cycloaddition of diazo compounds to [60]fullerene

Tuktarov¹,

Akhmetov²,

Korolev³

et al. 2010

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Dedicated to Professor Usein M. Dzhemilev on the occasion of his 65th birthday AbstractThe effective catalytic method for cycloaddition of higher diazoalkanes and diazoacetates to [60]fullerene in the presence of the three-component catalytic system Pd(acac) 2 -PPh 3 -Et 3 Al has been developed. The yield and selective formation of the target homo-and methanofullerenes are dependent upon the structure of the original diazo compounds.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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confidence: 99%

“…It is accompanied by the formation of a mixture of [6,6]-closed (methanofullerenes) and stereoisomeric [5,6]-open (homofullerenes) adducts.…”

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confidence: 99%

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confidence: 99%

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Palladium-catalyzed selective cycloaddition of diazo compounds to [60]fullerene

Tuktarov¹,

Akhmetov²,

Korolev³

et al. 2010

Arkivoc

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Cycloaddition of diazoketones to [60]fullerene in the presence of the catalytic system Pd(acac)2—PPh3—Et3Al

et al. 2010

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A method for the selective and efficient synthesis of methanofullerenes by cycloaddition of diazoketones to [60]fullerene in the presence of a three component catalytic system Pd(acac) 2 -PPh 3 -Et 3 Al has been developed.Functionally substituted fullerenes are of particular in terest and practical value. A great number of publications is devoted to the synthesis and physicochemical properties of these compounds. 1-7 The main part of these works is focused on the synthesis and study of the properties of homo and methanofullerenes, which synthesized by the Bingel reaction 8 as well as by thermal 9 or catalytical 10 cycloaddition of diazo compounds to [60]fullerene. The known synthetic methods toward cyclopropafullerenes by reaction of [60]fullerene with diazo compounds, includ ing diazoketones, 11-14 have little preparative significance due to low yields of the target methanofullerenes or re quire stoichiometric amounts of such expensive promot ers as ruthenium complexes. 9, 10 Recently, 15-18 we have reported the synthesis of homo and methanofullerenes in high yields by cycloaddition of diazo compounds (diazomethane, 15 diazoalkanes, 16 and diazoacetates 17,18 ) to [60]fullerene in the presence of pal ladium complexes. In continuation of this research, in the present work we studied cycloaddition of diazoketones to [60]fullerene in the presence of palladium complexes. The effect of the substituent in the starting diazoketone on the selectivity of the reaction and the yields of the target func tionalized methanofullerenes have also been studied. Results and DiscussionAmong a number of tested transition metal complexes, a three component catalyst prepared from Pd(acac) 2 , PPh 3 , and Et 3 Al (1 : 2 : 4) was found most efficient and selective in the reactions under study and in the reactions of [60]fullerene with diazoacetates as well. In this regard, all subsequent experiments were carried out using this cat alytic system. Cycloaddition of 2 oxo 2 phenyldiazo ethane to [60]fullerene was used as a model reaction. It is known that the reaction of 2 oxo 2 phenyldiazoethane with [60]fullerene at ~20 °C for 1 week resulted in a mix ture of cycloadducts 1-3 in the yield of ~30% (1 : 2 : 3 = 1 : 1 : 3). 14 We found that the reaction of 2 oxo 2 phenyldiazo ethane with [60]fullerene (reactant ratio 5 : 1, respectively) in the presence of a three component catalytic system Pd(acac) 2 -PPh 3 -Et 3 Al (1 : 2 : 4, 20 mol.%) at 80 °C (1 h, o dichlorobenzene) furnished exclusively 6,6 closed cy cloadduct 1 in ~40% yield (Scheme 1). No increase in the Scheme 1 i. N 2 CHC(O)Ph, Pd(acac) 2 -PPh 3 -Et 3 Al (1 : 2 : 4); ii. N 2 CHC(O)Ph

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Cycloaddition of diazocycloalkanes to [60]fullerene in the presence of Pd-containing complex catalyst

et al. 2010

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A catalytic method for the selective and efficient synthesis of cycloalkylidenehomofullerenes by cycloaddition of [60]fullerene to diazocycloalkanes generated in situ from the corresponding hydrazones in the presence of a complex catalytic system [Pd(acac) 2 -PPh 3 -Et 3 Al] has been developed.Despite the fact that homofullerenes are formed under kinetic control and methanofullerenes are more thermally stable products of the reaction of [60]fullerene with diazo compounds, the isolation of 5,6 open adducts in the indi vidual state is practically impossible. The only exceptions are the synthesis of homofullerenes by cycloaddition of diazomethane and other diazo compounds, which were generated in situ from the salts of the corresponding tosylhydrazones, to [60]fullerene. 1-6 The significant disadvantages of the known synthetic methods towards homofullerenes are low selectivity, 3-6 high sensitivity to changes in the temperature and the reaction time and low yields of the target cycloadducts.Recently, 7-9 we have reported the selective synthesis of homo and methanofullerenes in high yields by cyclo addition of diazomethane, 7 diazoalkanes, 8 and diazo acetates 9 to [60]fullerene in the presence of the palladium complexes. This reaction carried out in the presence of Pd(acac) 2 -PPh 3 -AlEt 3 (1 : 4 : 4) at 80 °C furnished ex clusively thermodynamically more stable 6,6 closed cyclo adducts (methanofullerenes). In continuation of this research, and with aim at studying the possibility of the synthesis of spirohomo and spiromethanofullerenes, in the present work we investigated cycloaddition of diazocycloalkanes, which were generated in situ by oxidation of the corresponding ketone hydrazones employing the known procedure, 10-12 to [60]fullerene in the presence of the complex catalyst Pd(acac) 2 -PPh 3 -Et 3 Al. The effect of the size of the cycle in starting diazo compound on the yield and selectivity of mono and dicycloaddition has also been studied. Results and DiscussionA three component catalyst prepared from Pd(acac) 2 , PPh 3 and Et 3 Al in a 1 : 2 : 4 ratio, respectively, turned out to be particularly efficient in the reactions of [60]fullerene with diazocycloalkanes and substituted diazomethanes. In this regard, all subsequent experiments were carried out using this catalytic system.It has been found* that the reaction of [60]fullerene with diazocyclopentane, which was generated in situ by oxidation of cyclopentanone hydrazone with MnO 2 (1 : 1.5 molar ratio), in the presence of a three compo nent catalyst Pd(acac) 2 -PPh 3 -Et 3 Al (1 : 2 : 4, 20 mol.%) at ~20 °C (1.5 h, toluene) resulted exclusively in spiro homofullerene 1 in ~70% yield (Scheme 1). Probably, the * Here and elsewhere the yields are given on the amount of the starting [60]fullerene used in the reactions. Scheme 1Reagents and conditions: Pd(acac) 2 : PPh 3 : Et 3 Al = 1 : 2 : 4, MnO 2 , 20 °C, 1.5 h.

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Catalytic cycloaddition of diazoalkanes generated in situ to fullerene C60

Cited by 16 publications

References 8 publications

Palladium-catalyzed selective cycloaddition of diazo compounds to [60]fullerene

Palladium-catalyzed selective cycloaddition of diazo compounds to [60]fullerene

Cycloaddition of diazoketones to [60]fullerene in the presence of the catalytic system Pd(acac)2—PPh3—Et3Al

Cycloaddition of diazocycloalkanes to [60]fullerene in the presence of Pd-containing complex catalyst

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