Synthesis of unsymmetrically substituted dodecakis(trifluoroethoxy)-phthalocyaninato vanadyl complexes

Three novel unsymmetrical vanadyl dodecakis(2,2,2-trifluoroethoxy)phthalocyaninates with nitro, amino or with no substitution were synthesized by a statistical condensation of 3,4,5,6-tetrakis(2,2,2-trifluoroethoxy)phthalonitrile with 4-nitro, 4-amino or 4-unsubstituted phthalonitrile, and separated by common column chromatography. These highly soluble phthalocyanines were characterized by elemental analysis, ir and ¹H-nmr, uv-visible and fast-atom-bombardment mass spectroscopy. Their uv-visible absorption spectra in solution and in doped poly(methyl methacrylate) films showed that they were less aggregated unsymmetrical phthalocyanines.     

Efficient salicylaldimine ligands for a palladium‐catalyzed Suzuki–Miyaura cross‐coupling reaction

A series of salicylaldimine ligands were designed to promote palladium‐catalyzed Suzuki–Miyaura cross‐coupling reaction. After a screening process, a ligand with a bulky 2,4‐di‐tert‐butyl substituent on the salicyaldehyde backbone and cyclohexylamine moiety was found to serve as a good combination for this reaction in aqueous solutions of DMF. The protocol demonstrated a significant advance in the efficiency of the cross‐coupling of aryl bromides and aryl chlorides with arylboronic acids to produce the desired biaryl products. Copyright © 2012 John Wiley & Sons, Ltd.     

Bi(III)‐catalyzed C―S cross‐coupling reaction

A direct synthetic route for the C―S coupling of aryl halides with thiophenols is described. This method is tolerant to electron‐withdrawing and electron‐donating functional groups and also to the presence of functional groups in the ortho position of the aryl iodide or thiophenol. Aryl iodides are coupled with thiophenols without affecting the other functionalities present in the aryl ring. These reactions follow second‐order kinetics. Copyright © 2012 John Wiley & Sons, Ltd.     

The palladium‐catalyzed C‐N cross‐coupling reaction of diheteroaryl disulfides with heterocyclic amines

The Pd‐catalyzed cross‐coupling reaction of 1, 2‐di(pyrimidin‐2‐yl) disulfides with heterocyclic amines including 2‐amino pyrimidines and 1,3,4‐thiadiazol‐2‐amines to deliver symmetrical C‐N coupling products in moderate to good yields is reported. This method provides an opportunity for synthesis of bioactive molecules and pharmaceutically interesting compounds containing heterocycle motifs. The reported protocol shows good functional group compatibility, and provides a new strategy for preparation of C2‐amination pyrimidine derivatives from heterocyclic disulfides.     

First palladium‐catalyzed denitrated coupling reaction of nitroarenes with phenols

The first palladium‐catalyzed protocol for the denitrated coupling reaction of nitroarenes with phenols has been developed, achieving unsymmetrical diaryl ethers in moderate to excellent yields. The cyclopalladated ferrocenylimine (catalyst Ic ) exhibited highly catalytic activity for this transformation with low catalyst loading (0.75 mol%) and short reaction time (2 h). The efficiency of this reaction was demonstrated by its compatibility with a range of groups. Moreover, the rigorous exclusion of air or moisture was not required in these transformations. Copyright © 2013 John Wiley & Sons, Ltd.     

Iron‐catalyzed cross‐coupling reaction: Heterogeneous palladium and copper‐free Heck and Sonogashira cross‐coupling reactions catalyzed by a reusable Fe(III) complex

An interesting silica‐supported iron catalyst was successfully prepared and demonstrated as an efficient heterogeneous catalyst for cross‐coupling reactions of aryl halides. The as‐prepared nanocatalyst was well characterized and found to be highly efficient in Heck reaction under mild and sustainable conditions (water as solvent at 80 °C in short reaction time). Furthermore, the obtained catalyst was used as an efficient, inexpensive and green heterogeneous catalyst for Sonogashira cross‐coupling reactions of various aryl iodides and provided the corresponding products with moderate to good yields. This phosphine, copper and palladium‐free catalyst was simply recovered from the reaction mixture and recycled five times without substantial decrease in its catalytic activity.     

Desulfinative palladium‐catalyzed cross‐coupling of arylsulfonyl hydrazides with aryl bromides under air

A highly efficient and mild palladium‐catalyzed cross‐coupling of arylsulfonyl hydrazides and aryl bromides for the selective synthesis of unsymmetrical biaryls has been developed. This methodology has the advantages of easily accessible starting materials, functional group tolerance and a wide range of substrates, which provide rapid access to biaryls derivatives. In this protocol, abundant and stable aryl bromides serve as the aryl sources by coupling reaction of the aryl group generated from arylsulfonyl hydrazides via in situ release of nitrogen and sulfur dioxide. No external oxidants or acids are needed for this kind of transformation.     

Crosslinkable hole‐transporting polymers by palladium‐catalyzed C—N‐coupling reaction

Combination of spin‐coating and crosslinking allows low‐cost fabrication of large area displays with multiple layers by simple solution processing. For this purpose, a series of novel crosslinkable polymers containing hole‐transporting triarylamine units in the main chain were synthesized via palladium‐catalyzed C—N‐coupling reaction. Additionally, they contain varying amounts of polymerizable oxetane groups as side chains. The polymers were photo‐crosslinked to yield absolutely insoluble networks. Thin films were used as hole‐transport layer in two‐layer blue light‐emitting diodes.     

Stacking patterns of thieno[3,2‐b]thiophenes functionalized by sequential palladium‐catalyzed Suzuki and Heck cross‐coupling reactions

The crystal structures of three 5‐alkenyl‐2‐arylthieno[3,2‐b]thiophenes, namely 3,6‐dibromo‐5‐(4‐tert‐butylstyryl)‐2‐(naphthalen‐1‐yl)thieno[3,2‐b]thiophene, C₂₈H₂₂Br₂S₂, (I), 3,6‐dibromo‐5‐(4‐methylstyryl)‐2‐(naphthalen‐1‐yl)thieno[3,2‐b]thiophene, C₂₅H₁₆Br₂S₂, (II), and 3,6‐dibromo‐2‐(4‐tert‐butylphenyl)‐5‐(4‐methylstyryl)thieno[3,2‐b]thiophene, C₂₅H₂₂Br₂S₂, (III), have been determined in order to evaluate the geometry of the molecules. The π‐conjugated system containing the thieno[3,2‐b]thiophene skeleton, the ethylene bridge and the phenyl rings is almost planar. The aromatic ring directly attached to the thieno[3,2‐b]thiophene moiety is not coplanar with the thieno[3,2‐b]thiophene moiety itself due to steric hindrance of the bromo substituent. The crystal packings are characterized by π–π stacking [only for (II)] and C—Br...π interactions. The long axes of the molecules in (I) are oriented in two directions; for the two other structures the long axis is oriented in one direction only.     

A convenient synthesis of 5‐alkylthio‐3,4‐diarylisoxazoles by palladium‐catalyzed coupling reactions

Palladium‐catalyzed coupling reaction was found effective for rapid access to pharmacologically interesting 3,4‐diarylisoxazoles derivatives as selective COX‐2 inhibitors. Thus, the coupling reaction between 5‐alkylthio‐3‐aryl‐4‐iodoisoxazoles and arylboronic acids afforded the target 5‐alkylthio‐3,4‐diarylisoxazoles in good yields.     

Catalytic activity of 1‐methylimidazole‐based phosphine ligands in the palladium‐catalyzed Suzuki coupling reaction

The catalytic activities of three N‐methylimidazole‐based phosphine ligands in the Suzuki coupling reaction were tested using PdCl₂ as the catalyst. The results showed all three phosphine ligands exhibited excellent activity towards the Suzuki reaction, and the catalytic activity decreased with increasing number of imidazole groups. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis of new methylated thieno[2,3‐a] and [3,2‐b]carbazoles by reductive cyclization of 6‐(2′‐Nitrophenyl)benzo[b]thiophenes obtained by palladium‐catalyzed cross‐coupling isabel

The synthesis of new methylated thieno[2,3‐a] and [3,2‐b]carbazoles (5) (R=H) was achieved by a palladium‐catalyzed cross‐coupling, intramolecular reductive cyclization sequence of reactions. The cyclization precursors 6‐(2′‐nitrophenyl)benzo[b]thiophenes (3) were obtained by Suzuki cross‐coupling of 6‐boronated methylbenzo[b]thiophenes intermediates (2) with 2‐bromo or iodonitrobenzene. The boronated intermediates (2) were prepared via bromine‐lithium exchange followed by boron transmetalation and coupled in situ using Pd(OAc)₂ giving thus a “one‐pot” three steps reaction from the 6‐bromobenzo[b]thio‐phenes (1) to the cyclization precursors (3) . In the reductive cyclization step, N‐ethylthienocarbazoles (5) (R=Et) were also obtained. Several experiments have been made varying the amount of triethylphosphite and the time of reaction, to avoid their formation.     

N‐functionalized azolin‐2‐ylidene‐palladium‐catalyzed heck reaction

Novel 1,3‐dialkylimidazolidinium, 1,3‐dialkyl‐3,4,5,6‐tetrahydropyrimidinium, and 1,3‐dialkyl‐1H‐4,5,6,7‐tetrahydrodiazepinium hexafluorophosphates ( 1a–c, 2a–c ) as N‐heterocyclic carbene precursors have been synthesized and characterized. The incorporation of saturated N‐heterocyclic carbenes into palladium precatalysts gives high‐catalyst activity in the Heck coupling of aryl bromide substrates in aqueous media. The complexes were generated in the presence of Pd(OAc)₂ by in situ deprotonation of 1,3‐dialkylazolinium salts 1, 2 . © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:82–86, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20415     

Novel saturated red‐emitting poly(p‐phenylenevinylene) copolymers with narrow‐band‐gap units of 2,1,3‐benzothiadiazole synthesized by a palladium‐catalyzed Stille coupling reaction

Novel poly(p‐phenylenevinylene) (PPV) copolymers derived from 1‐methoxy‐4‐octyloxyphenylene (MOP), 2,1,3‐benzothiadiazole (BT), and trans‐1,2‐bis(tributylstannyl)ethylene were first prepared by a palladium‐catalyzed Stille coupling reaction. The feed ratios of MOP to BT were 99.5:0.5, 99:1, 95:5, 85:15, 70:30, and 50:50. An efficient energy transfer from the 2‐methoxy‐5‐octyloxy‐p‐phenylenevinylene segment to the narrow‐band‐gap units was observed. The poly(2‐methoxy‐5‐octyloxy‐p‐phenylenevinylene‐2,1,3‐benzothiadiazolevinylene) copolymers emitted deep red light. The maximum electroluminescence emission of these PPV copolymers occurred at 659–724 nm and was accompanied by gradual redshifting with an increasing BT concentration. The photophysical properties were examined in comparison with those of copolymers based on BT and fluorene or N‐alkylcarbazole doped with the same BT concentration in the copolymer main chain. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2325‐2336, 2005     

Chugaev‐type bis(acyclic diaminocarbenes) as a new ligand class for the palladium‐catalyzed Mizoroki–Heck reaction

A series of differently substituted Chugaev‐type palladium bis(acyclic diaminocarbene) complexes was screened to identify the most active catalyst for Mizoroki–Heck coupling reactions of aryl bromides with styrene. The best catalyst, which contains three methyl groups on the bis(carbene) ligand, gives excellent coupling yields at 120 °C for both activated and deactivated aryl bromides. However, activity with aryl chlorides is limited to electron‐deficient examples. The optimized catalyst demonstrates limited air and moisture stability, giving reduced yields in couplings of activated aryl bromides in open‐flask conditions. The modular synthesis of this class of catalysts should allow further fine‐tuning of activity in Mizoroki–Heck and related coupling reactions. Copyright © 2012 John Wiley & Sons, Ltd.     

Carbon nanospheres with well‐controlled nano‐morphologies as support for palladium‐catalyzed Suzuki coupling reaction

Uniform carbon nanospheres (UCS) with well‐controlled nano‐morphologies were fabricated by hydrothermal carbonization of sucrose in the presence of kayexalate. Highly dispersed and ultrafine palladium nanoparticles were supported on the UCS through a facile co‐reduction process with NaBH₄ as reducing agent. The obtained Pd@UCS exhibited efficient catalytic activity for the Suzuki coupling reaction. Moreover, the as‐prepared catalyst could be recycled and reused at least five times without significant loss of its catalytic activity.     

Poly(ethylene glycol)‐ and glucopyranoside‐substituted N‐heterocyclic carbene precursors for the synthesis of arylfluorene derivatives using efficient palladium‐catalyzed aqueous Suzuki reaction

This paper reports an environmentally friendly and highly efficient synthesis of organic semiconductor materials via a Pd/N‐heterocyclic carbene (NHC)‐catalyzed Suzuki reaction in aqueous ethanol with high isolated yields (86–98%). Firstly, four glucopyranoside‐substituted NHC precursors with poly(ethylene glycol) (PEG) chains were synthesized and characterized. The NHC precursor with the longest PEG chain (n = 16) was found to be the most efficient ligand in the reactions of a wide range of aryl halides and arylboronic acids. The best catalyst system obtained in this work could be recycled five times without significant loss of catalytic activity.l Copyright © 2016 John Wiley & Sons, Ltd.     

Ammonium Chloride Promoted Palladium-Catalyzed UIImann Coupling of Aryl Bromide

In water, ammonium chloride was found to promote palladium-catalyzed Ullmann coupling reactions of aryl bromides. In the presence of Pd/C, zinc, NH4Cl, and water, coupling of various aryl bromides was carried out smoothly to afford the corresponding homocoupling products in moderate yields.     

Complex of [BMIm] PF6 with PEG1000: a high efficient and recycle system for palladium‐catalyzed Suzuki cross‐coupling and Heck reaction

A complex of [BMIm] PF₆ (1‐Butyl‐3‐methylimidazolium hexafluorophosphate) with PEG₁₀₀₀ has been successfully applied and found to be efficient for Suzuki cross‐coupling and Heck reaction using Pd(OAc)₂ as the catalyst under air atmosphere. Moreover, the isolation of the products is readily performed by the extraction of diethyl ether, and the catalytic system reported here can be recycled and reused several times. Copyright © 2012 John Wiley & Sons, Ltd.