Pd-catalyzed Sonogashira Reaction Research Articles

Synthesis of 5- and 6-Azaindoles by Sequential Site-Selective Palladium-Catalyzed C–C and C–N Coupling Reactions

Two-step sequential procedures for the Pd-catalyzed synthesis of 5- and 6-azaindoles are reported. The reactions proceed in very good yields. 6-Azaindoles are formed through site-selective Pd-catalyzed Sonogashira reaction of 3,4-dibromopyridine with alkynes, followed by a Pd-catalyzed tandem C–N coupling and cyclization with amines. On the other hand, 5-azaindoles are obtained by a site-selective Pd-catalyzed C–N coupling reaction of 3,4-dibromopyridine with amines, followed by C–C coupling and cyclization with alkynes.

Deep red aggregation-induced CPL emission behavior of four-component tunable AIE-active chiral polymers via two FRET pairs mechanism

Two four-component chiral polymers with two Förster resonance energy transfer (FRET) pairs incorporating chiral 1,1′-binaphthyl, 4,7- di(thiophen-2-yl)-2,1,3-benzothiadiazole (DTBT), tetraphenylethene (TPE) and fluorene moieties were designed and synthesized via one-pot two-step of Pd-catalyzed Sonogashira reaction and Suzuki reaction by changing different ratios of DTBT chromophore and AIE-active TPE group. Both chiral polymers exhibit large Stokes shift (257 nm) and tunable red aggregation-induced emission (AIE) response behavior via two intramolecular FRET pairs by changing excitation wavelength. Interestingly, the chiral polymer with lower ratio of DTBT (P-1) shows obvious aggregation-induced circularly polarized luminescence (AICPL) emission signals in deep red region (around 650 nm) and higher glum, which can reach as high as ±2.0 × 10-3 in THF-H2O mixtures.

Tunable AICPL of (S)-Binaphthyl-Based Three-Component Polymers via FRET Mechanism.

Five three-component chiral polymers incorporating (S)-1,1'-binaphthyl, tetraphenylethene (TPE) and fluorene moieties are designed and synthesized by Pd-catalyzed Sonogashira reaction. All these polymers show obvious aggregation induced emission enhancement response behavior in the fluorescence emission region of 460-480 nm. Interestingly, three of them show aggregation-induced circularly polarized luminescence (AICPL) signals in tetrahydrofuran-H2 O mixtures. Most importantly, these AICPL signals can be tuned by changing the molar ratios of TPE and fluorene components through fluorescence resonance energy transfer and give the highest glum = ±4.0 × 10-3 . This work provides a novel strategy for developing AICPL-enhanced materials.

Synthesis and optical properties of a novel sugar coated poly(p-phenyleneethynylene) effectively quenched by concanavalin A

The synthesis of a novel sugar coated poly(p-phenyleneethynylene) (PPE) via Pd-catalyzed Sonogashira reaction and its subsequent interaction with concanavalin A (Con A) are described. UV–Vis and fluorescence spectra were employed to investigate the response of the polymer toward various concentrations of Con A. The polymer showed a green fluorescence which can be quenched by Con A due to complex formation at ground state. The protocols reported herein provide intermediate products that can be converted into useful sensing elements from cheap and commercially available starting materials, in a few number of steps.

ChemInform Abstract: Recent Mechanistic Developments and Next Generation Catalysts for the Sonogashira Coupling Reaction

AbstractReview: 164 refs.

Recent mechanistic developments and next generation catalysts for the Sonogashira coupling reaction

The Pd-catalyzed Sonogashira reaction is a powerful method for the formation of Csp2–Csp bonds and has found application in a wide variety of areas including medicinal chemistry, agrochemistry, materials and electronics. Development of competent catalysts for the Sonogashira reaction is a particular scientific challenge since it is traditionally a di-metallic-mediated homogeneous catalytic process including some major drawbacks. This review provides a concise overview of the mechanistic aspects of the Cu co-catalyzed, Cu-free and Au-catalyzed Sonogashira coupling processes. More recent developments and next generation catalysts for the Sonogashira reaction are also presented. These include non transition-metal catalysts, metal free couplings and photo-induced protocols. Finally, the application of metal nanoparticles in Sonogashira reactions is presented. These include Pd nanoparticles, Pd bi- and tri-metallic nanoparticles, magnetically separable Pd/Fe3O4 nanoparticles, Ru nanoparticles and Au nanoparticles.

Synthesis of calix[4]arene derivatives via a Pd-catalyzed Sonogashira reaction and their recognition properties towards phenols

Abstract A novel series of calix[4]arene derivatives were synthesized via a Pd-catalyzed Sonogashira coupling reaction from para-substituted iodobenzene and 25,27-dipropargyl-calix[4]arene. Fluorescence studies found that nitro-phenols clearly exhibited quenching effects on 2c. Moreover, we minimized the free energy of the complexes by theoretical calculations. As the result, the π–π stacking interactions take place between the 4-nitrophenol and calix[4]arene, which may lead to the significant fluorescence quench.

Synthesis and Ultrafast Time Resolved Spectroscopy of Peripherally Functionalized Zinc Phthalocyanine Bearing Oligothienylene-ethynylene Subunits

Two new soluble tri-tert-butyl zinc(II) phthalocyanines, 1 and 2, bearing dendritic oligothienylene-ethynylene (DOT) groups as one of the peripheral substituents, have been prepared. The conjugated DOT moieties were introduced to cover the spectral window between 380 and 550 nm, where the ZnPc does not exhibit a strong absorption, in order to improve light harvesting. For their preparation, a convergent approach has been used starting from the corresponding iodoPc as precursor. Further transformation of the iodo groups by a Pd-catalyzed Sonogashira reaction with the appropriate DOT-functionalized terminal alkyne allowed the easy preparation of extended π-conjugated compounds 1 and 2. The compounds have been characterized by standard spectroscopic methods, and their photophysical behaviors have been established by using ultrafast time-resolved techniques. Femtosecond upconversion measurements showed an ultrafast energy transfer from the DOT to zinc phthalocyanine in a time scale of 300 fs. As the number of thiophene groups increases in the dyads, the extent of ultrafast energy transfer was found to increase. Compounds 1 and 2 have been tested as donor components in bulk heterojunction (BHJ) solar cells. Their efficiencies are compared with RuPc analogues previously reported by us.

Synthesis and Photovoltaic Properties of 1,8-Carbazole-Based Donor-Acceptor Type Conjugated Polymers

1,8-Diethynylcarbazole-based conjugated polymers were synthesized by the acetylenic oxidative coupling reaction or Pd-catalyzed Sonogashira reaction of the newly designed 3,6-dialkylated 1,8-diethynylcarbazole monomers. In particular, the Sonogashira polycondensation was effective for the preparation of donor–acceptor type alternating copolymers. The UV-vis absorption and fluorescence spectra of the polymers revealed the strength of the donor–acceptor interactions as well as their self-assembling features. The combination of electrochemical redox potentials and optical band gaps enabled the estimation of the polymer energy levels. The bulk-heterojunction solar cells composed of these promising polymers and PCBM exhibited a photoconversion efficiency (PCE) of 0.24%. It was determined that the partial doping of the bulk-heterojunction layer increased the open-circuit voltage (Voc), but decreased the short-circuit current (Jsc).

Polymer-based fluorescent sensor incorporating 2,2′-bipyridyl and benzo[2,1,3]thiadiazole moieties for Cu2+ detection

Abstract The polymer was synthesized by the polymerization of 4,4′-((4-iodophenoxy)methyl)-2,2′-bipyridine (M-1) with 4,7-diethynylbenzo[2,1,3]-thiadiazole (M-2) via Pd-catalyzed Sonogashira reaction. The fluorescence responses of the polymer towards various transition metal ions were investigated by fluorescence spectra and UV–Vis spectra. The polymer shows green fluorescence under ultraviolet lamp, which can be quenched by Cu2+ completely due to the heavy metal effect. The results suggested that the polymer can be used as a Cu2+-selective sensor via a naked eyes detecting mode.

A highly selective fluorescent sensor for Hg2+ based on the water-soluble poly(p-phenyleneethynylene)

The conjugated polymer P-1 could be synthesized by the polymerization of 4,7-diethynyl-benzo[2,1,3]thiadiazole (M-1) and 1,4-bis[3′-(N,N-diethylamino)-1′-oxapropyl]-2,5-diiodobenzene (M-2) via Pd-catalyzed Sonogashira reaction. The water-soluble conjugated polyelectrolyte P-2 could be obtained by the reaction of P-1 with ethyl bromide. Both P-1 and P-2 can emit orange fluorescence. The responsive optical properties of P-1 and P-2 on Hg2+ were investigated by fluorescence spectra. Hg2+ can lead to nearly complete fluorescence quenching of P-1. On the contrary, Hg2+ can show the most pronounced fluorescence enhancement response of P-2 in aqueous solution without interference from those coexistent ions, such as K+, Mg2+, Pb2+, Co2+, Ni2+, Ag+, Cd2+, Cu2+, Fe3+ and Zn2+. The results also exhibit that this kind of water-soluble conjugated polyelectrolyte can be used as a highly sensitive and selective fluorescence sensor for Hg2+ detection in water.

A highly selective and sensitive fluorescence chemosensor based on optically active polybinaphthyls for Hg 2+

The chiral polymer was synthesized by the polymerization of 4,7-diethynylbenzo[2,1,3]-thiadiazole ( M- 1) with ( R)-6,6′-dibutyl-3,3′-diiodo-2,2′-bis(diethylaminoethoxy)-1,1′-binaphthyl ( R - M- 1) via Pd-catalyzed Sonogashira reaction. The chiral polymer has orange fluorescence due to the extended π-electronic structure between binaphthyl unit and benzo[2,1,3]thiadiazole ( BT) group via ethynyl bridge. The responsive optical properties of the polymer on various metal ions were investigated by fluorescence spectra. The fluorescence of the chiral polymer can produce the pronounced enhancement as high as 1.8-fold upon addition of 1:2 molar ratio of Hg 2+. Compared with other cations, such as K +, Mg 2+, Pb 2+, Co 2+, Ni 2+, Ag +, Cd 2+, Cu 2+, Zn 2+, Mn 2+ and Fe 3+, Hg 2+ can produce the pronounced fluorescence response of the polymer. The result indicates this kind of chiral polybinaphthyls incorporating diethylamino and benzo[2,1,3]thiadiazole ( BT) moieties as receptors exhibits highly sensitive and selective behavior for Hg 2+ detection.

Synthesis and Fluorescent Properties of a Chiral Conjugated Polymer Based on (S)-2,2′-Binaphtho-20-crown-6

Abstract Linear conjugated polymer was obtained by the polymerization of 2,3-dibutoxy-1,4-diethynylnaphthalene (M-1) and (S)-5,5′-dibromo-6,6′-dibutyl-2,2′-binaphtho-20-crown-6 (S-M-2) via Pd-catalyzed Sonogashira reaction. The conjugated polymer shows strong green-blue fluorescence due to the extended π-electronic structure between the chiral repeating unit (S)-6,6′-dibutyl-2,2′-binaphtho-20-crown-6 and the conjugated linker 2,3-dibutoxynaphthyl group via acetylene bridge. The responsive properties of the chiral polymer on K+, Pb2+, Hg2+, and AsIII were investigated by fluorescent spectra. The results show that Hg2+ and AsIII can cause effective fluorescent quenching of the polymer, whereas, K+ and Pb2+ do not produce obvious changes in the polymer fluorescence. The obvious fluorescent influence shows that the 2,2′-binaphtho-20-crown-6 moiety plays an important role in fluorescent recognition for Hg2+ and AsIII due to the effective photoinduced electron transfer (PET) and charge transfer (PCT) between the conjugated polymer backbone and receptor species.