Luminescent Gold(I) Complexes with Tetrathia[7]helicene diphosphanes: photophysical and chiroptical properties

Gold(I) phosphine complexes exhibit significant biological activities that can be used for the development of novel therapeutic agents.1 In particular, a number of new gold(I) phosphine complexes displays a wide spectrum of anticancer activity, especially in some cisplatin-resistant cell lines,2 and their cytotoxicity was found to be mediated by targeting mitochondria and inducing apoptosis.3 In this context, innovative gold(I) complexes based on tetrathia[7]helicene phosphanes could represent a promising and interesting class of anticancer gold-based drugs. Tetrathia[7]helicenes (7-TH) are polyconjugated \uf070-systems, in which four thiophene rings alternate with three benzene rings, to form a non planar, chiral, stable helix which allows the existence of M and P antipodes.4 In the course of our studies on the applications of 7-TH derivatives in the field of the organometallic chemistry,5 we have synthesized and fully characterized the dinuclear gold(I) complex 1.6 The luminescence properties of Au(I) complex (\uf0b1)-1 at room and low temperature in diluted solution and in solid state, as well as the chiroptical properties of its antipodes have been investigated. In collaboration with the Fondazione IRCCS Istituto Nazionale dei Tumori of Milan, biological experiments to evaluate the cytotoxicity of enantiopure (\uf02d)-1 and (\uf02b)-1 against a panel of human cancer cell lines are in progress

Tetrathia[7]helicene Mono and Dinuclear Gold(I) Complexes

Tetrathia[7]helicenes (7-TH) are polyconjugated \uf070-systems in which four thiophene rings are orthofused to alternating arene rings to generate a non planar, chiral, stable helix which allows the existence of M and P enantiomers. The 7-TH systems are very interesting structures1 even because they can be easily and selectively functionalized in the alpha positions of the terminal thiophene rings,2 making it possible the introduction of appropriate substituents. In the course of our studies on the synthesis of phosphane derivatives of 7-TH as potential innovative chiral ligands in asymmetric organometallic catalysis,3 gold(I) complexes of the phosphines of 7,8-di-n-propyl-tetrathia[7]helicene 1 and 2 (Figure 1) provided promising results in some cycloisomerization reactions. Figure 1. Encouraged by these results, the two P and M enantiomers of gold(I) complex 1 have been synthesized, and completely characterized. The use of gold in homogeneous catalysis has witnessed tremendous activity in recent years.4 Thanks to gold(I) phosphine-based catalysts, various organic transformations have been accessible with both high yields and chemo- and stereoselectivity. In particular, asymmetric gold catalysis represents a very hot topic in catalytic research,5 and several efforts have been made by various research groups in this field

Gold(I) Complexes of Tetrathiaheterohelicene Phosphanes

New tetrathia[7]helicene-based (7-TH-based) gold(I) complexes 6 and 7 have been readily prepared by reaction of the respective phosphine ligands 2 and 3 with Au(tht)Cl in a 1:1 and 1:2 molar ratio, respectively. These complexes have been fully characterized by analytical and spectroscopic techniques as well as quantum chemical calculations. The molecular structure of dinuclear complex 7 has been determined by single-crystal X-ray diffraction, showing a gold 12gold interaction of 3.1825(3) \uc5 and a significant contraction of the 7-TH total dihedral angle. Au(I) complex 7 displays luminescence emission at room and low temperature in diluted solution and in the solid state. Quantum chemical calculations show that the luminescence emission at room temperature is primarily due to slightly perturbed fluorescence emission from purely \u3c0\u3c0* excited states of the conjugated helicene scaffold. At 77 K phosphorescence emission is displayed as well. Preliminary studies on the use of 6 and 7 as catalysts in typical Au(I)-catalyzed cycloisomerizations have demonstrated the reactivity of these systems in the intramolecular allene hydroarylations and the hydroxycarboxylation of allene-carboxylates

Facile and efficient one-pot synthesis of 2-arylbenzoxazoles using hydrogen tetrachloroaurate as catalyst under oxygen atmosphere*

In this paper, we presented a novel method for the facile and efficient one-pot synthesis of 2-arylbenzoxazoles, which were directly synthesized from 2-aminophenol and aldehydes catalyzed by hydrogen tetrachloroaurate (HAuCl4·4H2O) under an oxygen atmosphere with anhydrous tetrahydrofuran (THF) as solvent or in solvent-free condition. The results show that this method could bring excellent yields as high as 96%. THF was proven to be the best choice among several solvents screened and the reaction was tolerated with a variety of aromatic aldehydes possessing electron-donating or withdrawing groups. The advantages of the present method lie in catalytic process using economic and environmentally benign dioxygen as oxidant

Sodium tetrachloroaurate(III) dihydrate-catalyzed efficient synthesis of 1,5-benzodiazepine and quinoxaline derivatives*

Both 1,5-benzodiazepine and quinoxaline derivatives are important heterocycles in pharmaceuticals. We describe an efficient and clean method for the synthesis of 1,5-benzodiazepines from o-phenylenediamine and ketones catalyzed by sodium tetrachloroaurate(III) dihydrate under mild conditions. The catalyst was shown to be equally effective for the synthesis of quinoxalines from o-phenylenediamine and α-bromo ketones under the similar reaction conditions. This method produced good yields