Direct visible-light-induced synthesis of P-stereogenic phosphine oxides under air conditions.

Over the past two decades, visible-light-induced transformations have been regarded as being among the most environmentally benign and powerful strategies for constructing complex molecules and diverse synthetic building blocks in organic synthesis. However, the development of efficient photochemical processes for assembling enantiomerically pure molecules remains a significant challenge. Herein, we describe a simple and efficient visible-light-induced C-P bond forming reaction for the synthesis of P-chiral heteroaryl phosphine oxides in moderate to high yields with excellent ee values (97-99% ee). Even in the absence of transition metal or photoredox catalysts, a variety of P-chiral heteroaryl phosphine oxides, including chiral diphosphine oxide 41, have been directly obtained under air conditions. Density functional theory (DFT) calculations have shown that the reaction involves intersystem crossing and single electron transfer to give a diradical intermediate under visible light irradiation.

Transition metal complexes with functionalized indenyl phosphine ligands: structures and catalytic properties.

Transition-metal indenyl complexes usually exhibit different reactivities compared with their cyclopentadienyl analogues. Up to now, at least 10 metal-indenyl bonding modes have been reported. Because of the "indenyl effect", transition-metal indenyl complexes usually show enhanced reactivity in substitution and related reactions. This review provides an overview on the use and impact of indenyl phosphines in organometallic chemistry and transition-metal-catalysed reactions in the recent two decades. Some cationic and zwitterionic metal complexes supported by P,N-substituted indene or indenide ligands are described. They have been reported to induce the cleavage of E-H (E = H, Si and B) bonds and can be used as catalysts for addition of E-H bonds to unsaturated substrates. 2-Aryl indenyl phosphine ligands L3-L11 have been proven to be a class of versatile ligands for palladium-catalysed C-C and C-N cross-coupling reactions. Moreover, optically active tethered indenyl phosphine ligands can have better stereoselective control over the chirality arising at the metal center in the oxidative addition of their rhodium complexes with alkyl halides.

Synthesis of P-chiral phosphine compounds by palladium-catalyzed C-P coupling reactions.

An efficient C-P coupling reaction of enantiopure tert-butylmethylphosphine-boranes with aryl and heteroaryl halides is developed by using Pd(OAc)2/dppf as a catalyst, affording a series of (S) or (R)-P-chiral phosphines in moderate to high yields and with ee values up to 99% ee. Moreover, the reaction time could be reduced from 72 h to 6 h with increased ee values under microwave irradiation.

Transition-Metal-Catalyzed Regioselective Functionalization of Monophosphino-o-Carboranes.

A facile approach to the synthesis of diaryl- and dialkyl-substituted monophosphino-o-carboranes by rhodium(I)-catalyzed phosphine-directed B3,6 -H activation has been developed for the first time. Upon switching rhodium(I) to palladium(II), C-arylated and B6 -halogenated products were obtained by using tBuOLi and Li2 CO3 as base, respectively. These discoveries provide some simple and efficient approaches to the modification of monophosphino-o-carboranes.

Visible-Light-Promoted Transition-Metal-Free Phosphinylation of Heteroaryl Halides in the Presence of Potassium tert-Butoxide.

A novel visible-light-promoted C-P bond formation reaction in the absence of both transition metal and photoredox catalysts is disclosed. By employing easily available and inexpensive heteroaryl chlorides/bromides as substrates, a variety of heteroaryl phosphine oxides were obtained in moderate to good yields. This strategy provides a simple and efficient route to heteroaryl phosphine oxides.

Synthesis of peri-Substituted (Naphthalen-1-yl)phosphine Ligands by Rhodium(I)-Catalyzed Phosphine-Directed C-H Arylation.

A novel protocol for effective rhodium(I)-catalyzed C-H arylation of tertiary phosphines has been devised. It is amenable to a wide range of substrates and gives the products in moderate to high yields. This strategy provides a simple and efficient route to peri-substituted (naphthalen-1-yl)phosphines.

Application of a 2-aryl indenylphosphine ligand in the Buchwald-Hartwig cross-coupling reactions of aryl and heteroaryl chlorides under the solvent-free and aqueous conditions.

An efficient solvent-free protocol for the Buchwald-Hartwig cross-coupling reaction of aryl and heteroaryl chlorides with primary and secondary amines using the Pd(dba)2/ligand 1 catalytic system has been developed. Notably, the catalytic system also efficiently catalyzed the reaction under aqueous conditions.

An active catalytic system for Suzuki-Miyaura cross-coupling reactions using low levels of palladium loading.

An easily available Pd(OAc)2/(2-(anthracen-9-yl)-1H-inden-3-yl) dicyclohexylphosphine/toluene/iPrOH/water catalytic system was developed, which shows high catalytic activity in the Suzuki-Miyaura cross-coupling reactions of a diverse array of aryl and heteroaryl chlorides with Pd loadings down to 0.01 mol%.

Multistep Oxidation of Diethynyl Oligophenylamine-Bridged Diruthenium and Diiron Complexes.

Homo-dinuclear nonlinear complexes [{M(dppe)Cp*}2{µ-(-C≡C)2X}] (dppe = 1,2-bis(diphenylphosphino)ethane; Cp* = η5-C5Me5; X = triphenylamine (TPA), M = Ru (1a) and Fe (1b); X = N,N,N',N'-tetraphenylphenylene-1,4-diamine (TPPD), M = Ru (2a)) were prepared and characterized by 1H, 13C, and 31P NMR spectroscopy and single-crystal X-ray diffraction (1a, 2a). Attempts to prepare the diiron analogue of 2a were not successful. Experimental data obtained from cyclic voltammetry, square wave voltammetry, UV-vis-NIR (NIR = near-infrared) spectro-electrochemistry, and very informative IR spectro-electrochemistry in the C≡C stretching region, combined with density functional theory calculations, afford to make an emphasizing assessment of the close association between the metal-ethynyl termini and the oligophenylamine bridge core as well as their respective involvement in sequential one-electron oxidations of these complexes. The anodic behavior of the homo-bimetallic complexes depends strongly both on the metal center and the length of the oligophenylamine bridge core. The poorly separated first two oxidations of diiron complex 1b are localized on the electronically nearly independent Fe termini. In contrast, diruthenium complex 1a exhibits a significantly delocalized character and a marked electronic communication between the ruthenium centers through the diethynyl-TPA bridge. The ruthenium-ethynyl halves in 2a, separated by the doubly extended and more flexible TPPD bridge core, show a lower degree of electronic coupling, resulting in close-lying first two anodic waves and the NIR electronic absorption of [2a]+ with an indistinctive intervalence charge transfer character. Finally, the third anodic waves in the voltammetric responses of the homo-bimetallic complexes are associated with the concurrent exclusive oxidation of the TPA or TPPD bridge cores.

Elaborately Tuning Intramolecular Electron Transfer Through Varying Oligoacene Linkers in the Bis(diarylamino) Systems.

The research efforts on oligoacene systems are still relatively limited mainly due to the synthetic challenge and the extreme instability of longer acenes. Herein, these two issues have been overcome through elaborative modification and the stable pentacene species has been successfully synthesized. Additionally, a series of bis(diarylamino) compounds linked by variable-length oligoacene bridges ranging from one to five fused rings (benzene (1a), naphthalene (1b), anthracene (1c), tetracene (1d) and pentacene (1e)) have been prepared to probe the effect of the extent of π-conjugation on the electron transfer properties. Compound 1c exhibits a high planarity between the anthracyl bridge and the two nitrogen cores and the molecular packing shows a two-dimensional herringbone characteristic. Combined studies based on electrochemistry and spectroelectrochemistry demonstrate that (i) the electronic coupling across the oligoacene linkers between two diarylamine termini exponentially decrease with a moderate attenuation constant (ß) of 0.14 Å-1 in these length-modulated systems and (ii) the associated radical cations [1a]+-[1e]+ are classified as the class II Robin-Day mixed-valence systems. Furthermore, density functional theory (DFT) calculations have been conducted to gain insight into the nature of electron transfer processes in these oligoacene systems.

2-Aryl-indenylphosphine ligands: design, synthesis and application in Pd-catalyzed Suzuki-Miyaura coupling reactions.

A focused library of phosphine ligands was constructed for structural optimization. The catalyst can be used to perform the Suzuki-Miyaura cross-coupling reaction of aryl and heteroaryl chlorides.

An efficient indenyl-derived phosphine ligand for the Suzuki-Miyaura coupling of sterically hindered aryl halides.

An air-stable aryl substituted indenyl phosphine used in combination with Pd(OAc)2 provides a highly efficient catalyst for the Suzuki-Miyaura cross-coupling reaction of sterically hindered aryl halides with aryl boronic acids.

Pd-indenyl-diphosphine: an effective catalyst for the preparation of triarylamines.

A new Buchwald-type diphosphine ligand has been developed for applications in Pd-catalyzed amination reactions towards the preparation of triarylamines. The catalyst can be used to perform the amination of a diverse array of aryl and heteroaryl chlorides.

Asymmetric oxidation of vinyl- and ethynyl terthiophene ligands in triruthenium complexes.

A series of ruthenium(ii) complexes [{RuCl(CO)(PMe3)3(-CH[double bond, length as m-dash]CH-)}nX], (: n = 3, X = 3,3''-dimethyl-2,2':3',2''-terthiophene; : n = 2, X = 2,2'-bithiophene; : n = 2, X = 2,3-bis(3-methylthiophen-2-yl)benzothiophene) and [{Cp*(dppe)2Ru(-C[triple bond, length as m-dash]C-)}3X], (X = 3,3''-dimethyl-2,2':3',2''-terthiophene), were prepared and characterized by (1)H, (13)C and (31)P NMR. Their redox, spectroscopic and bonding properties were studied with a range of spectro-electrochemical methods in combination with density functional theory calculations. The first two anodic steps observed for and are largely localized on the lateral frameworks of the molecular triangle, the direct conjugation between them being precluded due to the photostable open form of the dithienyl ethene moiety. The third anodic step is then mainly localized on the centerpiece of the triangular structure, affecting both bithiophene laterals. The experimental IR and UV-vis-NIR spectroelectrochemical data and, largely, also DFT calculations account for this explanation, being further supported by direct comparison with the anodic behavior of reference diruthenium complexes and .

A novel carbazole-based gold(I) complex with interesting solid-state, multistimuli-responsive characteristics.

A new carbazole-based mononuclear gold(i) complex was designed and synthesized. The novel luminogen shows significative solid-state reversible mechanochromism, dual-responsive thermochromism and sensitive thin-film vapochromism properties. In addition, we obtained two kinds of crystals of the luminogen that may explain these interesting characteristics.

Efficient phosphine ligands for the one-pot palladium-catalyzed borylation/Suzuki-Miyaura cross-coupling reaction.

We report the synthesis of 2-(anthracen-9-yl)-1H-inden-3-yl dicyclohexylphosphine and its use in palladium-catalyzed borylation/Suzuki-Miyaura cross-coupling reaction to prepare a variety of symmetrical and unsymmetrical biaryl compounds in excellent yield.

A novel fluorene-based aggregation-induced emission (AIE)-active gold(i) complex with crystallization-induced emission enhancement (CIEE) and reversible mechanochromism characteristics.

A new fluorene-based AIE-active gold(i) complex was designed and synthesized. The novel luminogen exhibits a crystallization-induced emission enhancement (CIEE) effect and reversible mechanochromic behavior with fluorescence changes between green and yellow emissions.

Chemical control of photochromism and a multiresponsive molecular switch based on a diarylethene derivative containing naphthol.

A photochemically inactive diarylethene derivative with a naphthol group bridging through the imidazole unit (DIN) was synthesized to characterize a multifunctional switch. Upon stimulation by radiation (UV and visible light), the target diarylethene derivative DIN was not photochemically inactive but photo-active, it could be photo-converted into a keto compound. Moreover, the photochromic reaction of DIN was observed when it was stimulated by the addition of acid or methylation. Fluorescence quenching and the bathochromic effect occurred when DIN was stimulated by the addition of copper ions and a base, respectively. Its optical properties could be regulated by various chemical stimuli. Thus, it can potentially be utilized as a multiresponsive molecular switch.

Synthesis and molecular recognition studies on small-molecule inhibitors for thioredoxin reductase.

Thioredoxin reductase (TrxR), which is overexpressed in many aggressive cancers, plays a crucial role in redox balance and antioxidant function, including defense of oxidative stress, control of cell proliferation, and regulation of cell apoptosis. Deactivation of TrxR can destroy the homeostasis of the cancer cells, inducing elevation of reactive oxygen species (ROS) levels and the oxidation of enzymatic substrates. Here, we synthesized and identified a new gold(I) small molecule (D9) that possesses two strong electron-donating moieties, i.e., 4-methylphenyl alkynyl and thionyldiphenyl phosphine, exhibiting an enhanced p-π conjunction effect. The resulting compound shows the increased soft Lewis acids and the stability of gold(I). And we demonstrated that D9 could efficiently and specifically inhibit the activity of TrxR in vitro and in vivo, and it could effectively avoid the ligand exchange with albumin that was one of the most abundant proteins in blood. We believe that these comprehensive studies on the relationship between the structure and performance will provide inspiring information on the precise synthesis and design of new compounds for targeting TrxR.

A novel fluorene-based gold(I) complex with aggregate fluorescence change: a single-component white light-emitting luminophor.

A new fluorene-based white light-emitting gold(I) complex with aggregate fluorescence change is reported. The novel luminogen emits direct white light in the solid state without involving complex doping/mixing procedures.