Tether‐Directed Bisfunctionalization Reactions of C60 and C70

Four easily isolable regio‐ and stereoselective bis‐adducts of C₆₀ and C₇₀, as well as a new C₇₀‐dumbbell derivative, have been synthesized by using two different bismalonate tethered moieties. The derivatives that possess relatively long‐tethered moieties show highly symmetric addition patterns, as evidenced by spectroscopic measurements, whereas the derivatives possessing the shorter‐tethered moiety exhibit interesting addition patterns on C₆₀ and C₇₀.     

C60‐Mediated Molecular Shape Sorting: Separation and Purification of Geometrical Isomers

A supramolecular crystallization‐based approach has been developed for the shape‐dependent separation of geometrical isomers under near‐ambient conditions. Difficulties to separate such isomers arise because of their very similar physical properties. The present approach relies on the ability of C₆₀ to preferentially form solvate crystals with molecules of a specific geometry. Subsequently, these molecules are released upon mild heating to regenerate pure C₆₀. By taking isomers of xylene and trimethylbenzene (TMB) as examples, we show that one of the isomers can be extracted from the rest with very high purity. To separate TMB isomers, a new C₆₀–1,3,5‐TMB solvate was developed, which led to the isolation of isomer purities greater than 99.6 %. Versatility, a low operating temperature of approximately 100 °C, a separation efficiency of more than 10 weight % of C₆₀ per cycle, and reagent recyclability makes this a promising molecular shape‐sorting approach.     

Organoaluminum‐Mediated Direct Cross‐Coupling Reactions

We present a direct cross‐coupling reaction between arylaluminum compounds (ArAlMe₂?LiCl) and organic halides RX (R=aryl, alkenyl, alkynyl; X=I, Br, and Cl) without any external catalyst. The reaction takes place smoothly, simply upon heating, thereby enabling the efficient and chemo‐/stereoselective formation of biaryl, alkene, and alkyne coupling products with broad functional group compatibility.     

Exploration of Dimethylzinc‐Mediated Radical Reactions

In this account, our studies on radical reactions that are promoted by dimethylzinc and air are described. Advantages of this reagent and differences from conventional radical initiators, such as triethylborane, are discussed.     

ω‐Fluoro Thiafatty Acids: New Mechanistic Probes of Desaturase‐Mediated Reactions

A series of 18‐fluoro thiastearates were prepared and incubated with a yeast Δ9‐desaturating system. The relative efficiency of desaturase‐mediated sulfoxidation was monitored via ¹⁹F‐NMR analysis of the sulfoxide products, and a strong preference for oxo transfer to the S‐atom occupying the 9‐position was confirmed. The oxidation profile obtained in this manner matched that of analogous experiments with non‐fluorinated substrates. These results form the basis of a versatile ¹⁹F‐NMR‐based method for mapping the position of the putative diiron oxidant relative to substrate, and has potential application to the study of membrane‐bound desaturases in vitro.     

Ultrasound‐Mediated Synthesis of Novel 1,2,3‐Triazole‐Based Pyrazole and Pyrimidine Derivatives as Antimicrobial Agents

In the development of novel antimicrobial agents, we synthesized novel 1,2,3‐triazole‐based pyrazole and pyrimidine derivatives 6 ( a–f ) and 7 ( a–f ) by ultrasound‐assisted method. The synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR, MS, and elemental analysis. All compounds were assessed in vitro for their efficacy as antimicrobial agents against four bacteria (Staphylococcus aureus , Bacillus subtilis , Escherichia coli , and Pseudomonas aeruginosa ) and two fungi (Candida albicans and Aspergillus niger ). In particular, compounds 6a , 6e , 7a , 7c , and 7e exhibited highly potent antimicrobial activity.     

Copper‐Mediated C6‐Selective Dehydrogenative Heteroarylation of 2‐Pyridones with 1,3‐Azoles

A copper‐mediated C6‐selective dehydrogenative heteroarylation of 2‐pyridones with 1,3‐azoles has been developed. The reaction proceeded smoothly by twofold C? H cleavage even in the absence of noble‐metal catalysts. The observed site selectivity was directed by a pyridyl substituent on the nitrogen atom of the pyridone ring. This directing group was readily removed after the coupling event, thus leading to 2‐pyridone derivatives with a free N? H group. Moreover, in some cases, catalytic turnover of the Cu salt was also possible with the ideal terminal oxidant: molecular oxygen in air.     

Powerful Bispyridinylidene Organic Reducing Agents with Iminophosphorano π‐Donor Substituents

Four members of a new family of powerful bispyridinylidene organic reducing agents have been prepared, which exploit iminophosphorano (?N=PR₃; R=Ph, Cy) π‐donor substituents. Electrochemical studies show exceptionally high oxidation potentials, ranging from 1.30 to 1.51 V versus SCE. These new reductants were shown to effectively convert 1‐bromonaphthalene to naphthalene under mild reaction conditions. From the redox potentials, substituent constants (σ_p⁺) for the iminophosphorano groups Ph₃P=N? (?1.82) and Cy₃P=N? (?2.21) were determined, demonstrating their superior π‐donating properties compared to traditional amino substituents.     

GaCl3‐Mediated Reactions of Donor–Acceptor Cyclopropanes with Aromatic Aldehydes

A new strategy for cascade assembly of substituted indenes and polycyclic lactones based on reactions of donor–acceptor cyclopropanes and styrylmalonates with aromatic aldehydes in the presence of GaCl₃ has been developed. The use of GaCl₃ makes it possible to principally change the direction of the reaction known in this series of substrates and to perform the process in a multicomponent version. Generation of formal 1,2‐zwitterionic intermediates owing to complexation of dicarboxylate groups with GaCl₃ is the driving force of the reactions discovered. This method makes it possible to assemble indenylmalonates or indano[1′,2′:2,3]indano[2,1‐b]furan‐2‐ones in one synthetic stage from readily available starting compounds with high regio‐ and diastereoselectivity. A mechanism of the reactions has been suggested using the ¹⁸O label in benzaldehyde.     

Gas‐phase fragmentation of protonated C60‐pyrimidine derivatives

Electrospray ionization mass spectrometry/mass spectrometry (ESI/MS/MS) and multiple stage mass spectrometry (MSⁿ, n > 2) were used in the positive ion mode, with two different types of mass spectrometers, a quadrupole time‐of‐flight and an ion trap, to characterize two sets of different types of C₆₀‐aminopyrimidine exohedral derivatives. In one set, the pyrimidine moiety bears an amino acid methyl ester residue, and in the other the pyrimidine ring is part of a nucleoside‐type moiety, the latter existing as two separated diastereoisomers. We have found that retro‐cycloaddition processes occur for the closed shell protonated species formed by electrospraying C₆₀ derivatives synthesized by Diels–Alder reactions, whereas for the C₆₀ derivatives synthesized via 1,3‐dipolar cycloadditions, these processes did not occur. Formation of diagnostic ions allowed the differentiation between the two groups of fullerene derivatives, and between the diastereoisomers of C₆₀ derivatives with a nucleoside‐type moiety. In general, the fragmentation processes are strongly dependent on the protonation sites and on the structure of the exohedral moieties. Copyright © 2009 John Wiley & Sons, Ltd.     

Metal‐Free‐Mediated Oxidation Aromatization of 1,4‐Dihydropyridines to Pyridines Using Visible Light and Air

A metal‐free and environmentally friendly aerobic aromatization photosensitized by organic dye eosin Y bis(tetrabutyl ammonium salt) (TBA‐eosinY) has been developed. With the aid of K₂CO₃, the aerobic catalytic system converts 1,4‐dihydropyridines to their corresponding pyridine derivatives efficiently under visible light irradiation (λ=450 nm) at room temperature.     

Properties and Reactions of Substituted 1,2‐Thiazetidine 1,1‐Dioxides: Functionalization and Reactions at C(4) of the β‐Sultam

The introduction of functional groups at the 4‐position of the β‐sultam ring was realized by the synthesis of mono‐ and disubstituted derivatives by reactions of N‐silylated β‐sultams with electrophiles in the presence of BuLi or LDA. As electrophiles, ketones, chlorosilanes, a β‐sultam, CO₂, chloroformiate, halogen, azodicarboxylate, phenyltriazoledione, tosyl azide, 1,3,5‐triazine, propyl nitrate, and phenyl isocyanate were used. Furthermore, a number of derivatives of these substitution products were synthesized. All products were characterized by standard spectroscopic methods, and conformations were studied, supported by calculation.