Fluorescent Azasteroids through Ultrasound Assisted Cycloaddition Reactions

We report here the synthesis and optical spectral properties of several new azasteroid derivatives. The formation of these compounds was explained based on the most probable mechanism. The luminescent heterocycles were synthesized by 1,3-dipolar cycloaddition reactions between benzo[f]quinoline and methylpropiolate or dimethyl acetylenedicarboxylate (DMAD). A selective and efficient way for [3+2]-dipolar cycloaddition of benzo[f]quinolinium ylides under ultrasound (US) irradiation (20 kHz processing frequency) is presented. We report substantially higher yields under US irradiation, whereas the solvent amounts required are at least three-fold less compared to classical heating. The azasteroid derivatives are blue emitters with λmax of fluorescence around 430–450 nm. A certain influence of the azasteroid substituents concerning absorption and fluorescent properties was observed. Compounds anchored with a bulky pivaloyl group or without a C=O carbonyl group have shown increased fluorescence intensity.

Synthesis of 1-(2-Fluorophenyl)pyrazoles by 1,3-Dipolar Cycloaddition of the Corresponding Sydnones

3-Arylsydnones bearing fluorine and bromine atoms on the benzene ring were synthesized from N-nitroso-2-fluorophenylglycines and characterized by NMR spectroscopy. These were employed further in synthesis of the corresponding 1-(2-fluorophenyl)pyrazoles by 1,3-dipolar cycloaddition reaction with dimethyl acetylenedicarboxylate (DMAD) as activated dipolarophile. The sydnones as reaction intermediates were characterized by single crystal X-ray diffraction analysis showing interesting features such as halogen bonding as an important interaction in modeling the crystal structure.

Efficient and Facile Synthesis of Chromenopyrano[2,3-b] pyridine Derivatives Catalyzed by Sodium Carbonate

In this research, a number of new and known chromenopyrano[2,3-b]pyridine derivatives have been prepared. Initially, according to the reported procedure, pyrano[2,3-c]chromene derivatives were synthesized by the reaction between 4-hydroxycoumarin, aromatic aldehydes and malononitrile using silica sodium carbonate (SSC) as the catalyst. Next, the prepared pyrano[2,3-c]chromenes were reacted by dimethyl acetylenedicarboxylate (DMAD) or cyclohexanone in the presence of sodium carbonate to produce chromenopyrano[2,3-b]pyridine derivatives. The presented protocol avoids the use of expensive catalysts and gives useful potentially bioactive heterocycles in excellent to high yields.

Diels-Alder Additions to 2,2’-Biaceanthrylene

A series of Diels-Alder reactions between the diene 2,2’-biaceanthylene and several dienophiles is presented. The diene is a cyclopenta-fused polycyclic aromatic hydrocarbon with anthracene units linked by two cyclopentene rings. Depending on the dienophile, the major product was the result of a single addition (dimethyl acetylenedicarboxylate) or double addition (quinone, benzyne) to the diene. Single crystal X-ray analysis of the quinone-derivative shows a propeller-like structure composed of mixed enantiomers. The synthesis and photophysical properties of these compounds is presented.<br>

Diels-Alder Additions to 2,2’-Biaceanthrylene

A series of Diels-Alder reactions between the diene 2,2’-biaceanthylene and several dienophiles is presented. The diene is a cyclopenta-fused polycyclic aromatic hydrocarbon with anthracene units linked by two cyclopentene rings. Depending on the dienophile, the major product was the result of a single addition (dimethyl acetylenedicarboxylate) or double addition (quinone, benzyne) to the diene. Single crystal X-ray analysis of the quinone-derivative shows a propeller-like structure composed of mixed enantiomers. The synthesis and photophysical properties of these compounds is presented.<br>

Vinylidene, allenylidene, cyclic oxycarbene, and η2-alkyne complexes from reactions of (η5-C5Me5)OsCl(PPh3)2 with alkynes and alkynols

Reactions of Cp*OsCl(PPh3)2 (Cp* = pentamethylcyclopentadienyl) with alkynes and alkynols are described. Treatment of Cp*OsCl(PPh3)2 with phenylacetylene and trimethylsilylacetylene gave the vinylidene complexes Cp*OsCl(=C=CHPh)(PPh3) and Cp*OsCl(=C=CH2)(PPh3), respectively. Treatment of Cp*OsCl(PPh3)2 with the internal alkyne dimethyl acetylenedicarboxylate produced the η2-alkyne complex Cp*OsCl(η2-MeO2C≡CCO2Me)(PPh3). Treatment of Cp*OsCl(PPh3)2 with the propargylic alcohol HC≡CC(OH)Ph2 gave the osmium allenylidene complex Cp*OsCl(=C = C=CPh2)(PPh3). The outcomes of the reactions of Cp*OsCl(PPh3)2 with ω-alkynols HC≡C(CH2)nOH are dependent on the length of the -(CH2)n- linker. The reaction with 3-butyn-1-ol produced the cyclic oxycarbene complex Cp*OsCl{=C(CH2)3O}(PPh3) exclusively. The reactions with 4-pentyn-1-ol produced a mixture of the hydroxyalkyl vinylidene complex Cp*OsCl{=C=CH(CH2)3OH}(PPh3) and the cyclic oxycarbene complex Cp*OsCl{=C(CH2)4O}(PPh3) in about 10:1 molar ratio. The reaction with 5-hexyn-1-ol gave exclusively the hydroxyalkyl vinylidene complex Cp*OsCl{=C=CH(CH2)4OH}(PPh3).

Tetramethyl 1,1′-(2-[{4,5-bis(Methoxycarbonyl)-1H-1,2,3-triazol-1-yl}methyl]-2-[(4-methylphenyl)sulfonamido]propane-1,3-diyl)bis(1H-1,2,3-triazole-4,5-dicarboxylate)

A new compound tetramethyl 1,1′-(2-[{4,5-bis(methoxycarbonyl)-1H-1,2,3-triazol-1-yl}methyl]-2-[(4-methylphenyl)sulfonamido]propane-1,3-diyl)bis(1H-1,2,3-triazole-4,5-dicarboxylate) (3) was prepared in two steps starting from 2-((4-methylphenyl)sulfonamido)-2-((tosyloxy)methyl)propane-1,3-diylbis(4-methylbenzenesulfonate) (1), with an overall yield of 74%. The key step being the copper-free Huisgen cycloaddition between N-(1,3-diazido-2-(azidomethyl)propan-2-yl)-4-methylbenzenesulfonamide (2) and commercially available dimethyl acetylenedicarboxylate. The chemical structure of compound 3 was determined by IR, 1D and 2D NMR experiments, and elemental analysis.

Fullerene C60 promoted photochemical hydroamination reactions of an electron deficient alkyne with trimethylsilyl group containing tertiary N-alkylbenzylamines

C60-promoted photoaddition reactions of N-α-trimethylsilyl-N-alkylbenzylamines with dimethyl acetylenedicarboxylate (DMAD) were carried out.

Application of highly efficient and reusable H3PW12O40/Fe3O4@SiO2-Pr-Pi nanocatalyst for preparation of dihydro-2-oxypyrrole derivatives

In this study, a novel heterogeneous catalyst (H3PW12O40/Fe3O4@SiO2-Pr-Pi) was prepared via immobilization of H3PW12O40 on the surface of piperidine modified magnetic nanoparticles (Fe3O4@SiO2-Pr-Pi). The synthesis of dihydro-2-oxypyrrole derivatives was carried out by the reaction of substituted aniline, formaldehyde, and dimethyl acetylenedicarboxylate, promoted by H3PW12O40/Fe3O4@SiO2-Pr-Pi in EtOH. The formation of resultant catalyst was confirmed by FTIR spectroscopy, FE-SEM, EDX, VSM, and TGA techniques. The magnetically separable and environmentally friendly nanostructured catalyst remained quite stable during reaction conditions and was reused for at least five recycle runs.