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

Abstract

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.

Sulfur-Containing Homo- and Methanofullerenes: Synthesis and Study of Tribological Properties

“…It was found that in the interaction of C 60 -fullerene with a 1.5-fold excess of 2-diazo-3-(pentylthiomethyl)-or 2-diazo-3-(cyclohexylthiomethyl)butane, generated in situ by the oxidation of hydrazones of the corresponding ketones, in the presence of 20 mol% of the three-component catalyst Pd(acac) 2 -PPh 3 -Et 3 Al (1:2:4) at room temperature (18-20 • C) in chlorobenzene, the corresponding homofullerenes 1 and 2 are formed in 1 h with a yield of ~50% [21] (Scheme 1).…”

“…It was found that in the interaction of C60-fullerene with a 1.5-fold excess of 2-diazo-3-(pentylthiomethyl)-or 2-diazo-3-(cyclohexylthiomethyl)butane, generated in situ by the oxidation of hydrazones of the corresponding ketones, in the presence of 20 mol .% of the three-component catalyst Pd(acac)2-PPh3-Et3Al (1:2:4) at room temperature (18-20°C) in chlorobenzene, the corresponding homofullerenes 1 and 2 are formed in 1 h with a yield of ~50% [21] (Scheme 1). Under the developed optimal conditions (~20-22 °C, 1 h, 20 mol.% Pd(acac)2-PPh3-Et3Al (1:2:4)), the cycloaddition of sulfur-containing diazoalkanes generated in situ from hydrazones of 4-methylthiobenzaldehyde and 2-acetylthiophene to C60-fullerene leads to compounds 3 and 4 in 50 and 45% yields, respectively (Scheme 2).…”

“…In this regard, all experiments on the study of the reaction of the catalytic cycloaddition of sulfurcontaining diazoalkanes to C60-fullerene were carried out in the presence of this catalytic system. It was found that in the interaction of C60-fullerene with a 1.5-fold excess of 2-diazo-3-(pentylthiomethyl)-or 2-diazo-3-(cyclohexylthiomethyl)butane, generated in situ by the oxidation of hydrazones of the corresponding ketones, in the presence of 20 mol .% of the three-component catalyst Pd(acac)2-PPh3-Et3Al (1:2:4) at room temperature (18-20°C) in chlorobenzene, the corresponding homofullerenes 1 and 2 are formed in 1 h with a yield of ~50% [21] Under the developed optimal conditions (~20-22 °C, 1 h, 20 mol.% Pd(acac)2-PPh3-Et3Al (1:2:4)), the cycloaddition of sulfur-containing diazoalkanes generated in situ from hydrazones of 4-methylthiobenzaldehyde and 2-acetylthiophene to C60-fullerene leads to compounds 3 and 4 in 50 and 45% yields, respectively (Scheme 2). Analysis of the 1H and 13C Nuclear Magnetic Resonance (NMR) spectra, as well as the UV spectra, of compound 4 showed that the reaction of C60 with a diazo compound containing a thienyl fragment resulted in the formation of only a [2+1]-cycloadduct of a closed structure.…”

Catalytic Cycloaddition of Diazo Compounds Based on Pharmacologically Significant and Natural Compounds to C60-Fullerene †

“…Diazoacetates containing cholesterol in the ester group [23], α-tocopherol, Trolox methyl esters, 20.29-dehydrobetulic, and ursolic acids [24], which have antioxidant, antitumor, and antiviral properties, were used as the initial pharmacological objects of the study. It has been shown that the above diazo compounds interact with C 60 -fullerene (molar ratio 5:1) in the presence of 20 mol.% of the three-component catalyst Pd(acac) 2 -PPh 3 -Et 3 Al, taken in a ratio of 1:4:4 at 80 • C, for 1 h in 1,2-dichlorobenzene, the corresponding methanofullerenes 1-5 are selectively formed with a yield of 60-75% (Scheme 1).…”

Carbene Additions to Fullerenes

“…They employed Pd(OAc) 2 in the reaction of ethereal diazomethane with C 60 at 0 °C and isolated the methanofullerene in 15% yield. Tuktarov and co-workers developed three-component catalytic systems Pd(acac) 2 –PPh 3 –Et 3 Al to improve the efficiencies of cycloadditions. − The formation ratio of the adducts depends on the substituents of the diazo compounds they used and the reaction conditions. When diazoesters or diazoketones were used for the three-component Pd(acac) 2 –4PPh 3 –4Et 3 Al catalytic reactions, [6,6] closed methanofullerenes were obtained exclusively in 30–60% yields.…”