The Heck Reaction in Ionic Liquids: Progress and Challenges

As   the   interest   for   environmental   increases   and   environmental   laws   become   more   stringent,   the   need   to   replace   existing   processes   with   new   more   sustainable   technologies   becomes   a   primary   objective.   The   use   of   ionic   liquids   to   replace   organic   solvents  in  metal  catalyzed  reactions  has  recently  gained  much  attention  and  great  progress   has   been   accomplished   in   this   area   in   the   last   years.   This   paper   reviews   the   recent   developments   in   the   application   of   ionic   liquids   and   related   systems   (supported   ionic   liquids,  ionic  polymers,  and  so  on)  in  the  Heck  reaction.  Merits  and  achievements  of  ionic   liquids   were   analyzed   and   discussed   considering   the   possibility   of   increasing   the   effectiveness  of  industrial  processes

Development and applications of highly selective palladium-catalyzed monocoupling reactions of (cyclo)alkenes and 1,3-alkadienes bearing two or three electrophilic sites and bis(enol triflates) with terminal alkynes

The motivation for writing this review with 558 references, which covers the literature up to the end of September 2012, is to fill a part of this gap by illustrating highly selective Pd/Cu-catalyzed and Cu-free Pd-catalyzed monoalkynylation reactions of (cyclo)alkenes and 1,3-butadienes bearing two or three identical or different electrophilic sites and bis(enol triflates) with terminal alkynes. However, Pd-catalyzed selective monocoupling reactions of 1-alkynes with (hetero)aryl halides or pseudohalides with two identical or different electrophilic sites will not be covered. Moreover, Pd-catalyzed monocoupling reactions of 1-alkynes with non-conjugated diene systems bearing an electrophilic site on each carbon–carbon double bond have also been considered to be beyond the scope of this review. In addition to describing and commenting on the aforementioned monoalkynylation reactions of (cyclo)alkenes and 1,3-dienes with two or three identical or different electrophilic sites and bis(enol triflates), emphasis has been placed on the use of Pd-catalyzed monoalkynylations of (cyclo)alkenes and 1,3-butadienes bearing two or three identical or different electrophilic sites and bis(enol triflates) as key steps of the syntheses of core structures and models of enediyne antitumor antibiotics, pharmacologically active compounds, and bioactive naturally occurring compounds including insect sex pheromone components, and fungal and plant metabolites. Moreover, the review has been focused on the formation of disubstituted acetylenic derivatives by one-pot site-selective Pd-catalyzed consecutive alkynylation reactions of di(pseudo)halogenated olefinic substrates with two different terminal alkynes. Where appropriate, the reasons for the observed stereo-, site-, and/or chemoselectivities of the reported Sonogashira-type monoalkynylation reactions have been mentioned and discussed

Transition Metal-Free Direct C-H (Hetero)arylation of Heteroarenes: A Sustainable Methodology to Access (Hetero)aryl-Substituted Heteroarenes

In recent years, environmental and economic reasons have motivated the development of transition metal-free carbon-carbon bond forming reactions and some excellent reviews have covered this research area of particular interest for the pharmaceutical industry. However, none of these reviews has been specifically dedicated to summarize and discuss the results achieved in the rapidly growing field of the transition metal-free direct (hetero)arylation reactions of heteroarenes. This review, which covers the literature from 2008 to 2014, aims to provide a thorough insight into the synthetic and mechanistic aspects of these atom economic and environmentally benign reactions also highlighting their advantages and possible disadvantages compared to conventional methods for the synthesis of arylheteroarenes and biheteroaryls via transition metal-catalyzed reactions

Synthesis and Biological Properties of 2(5H)-Furanones Featuring Bromine Atoms on the Heterocyclic Ring and/or Brominated Substituents

This review deals with the synthesis of unnatural and natural 2(5H)-furanone derivatives featuring bromine atoms on the heterocyclic ring and/or brominated substituents, which have been described in the literature since 1951 up to February 2016. The review has been organized on the basis of six classes of brominated furanone derivatives that were synthesized: i) 2(5H)-furanone derivatives with one bromine atom on the heterocyclic ring; ii) 2(5H)-furanone derivatives with two bromine atoms on the heterocyclic ring; iii) 2(5H)-furanone derivatives featuring one bromine atom on the heterocyclic ring and monobrominated substituents; iv) 2(5H)- furanone derivatives featuring one bromine atom on the heterocyclic ring and dibrominated substituents; v) 2(5H)-furanone derivatives with monobrominated substituents; and vi) 2(5H)-furanones featuring dibrominated substituents. Where possible, experimental details of the syntheses have been reported. Furthermore, the biological properties of the target compounds, including their mutagenic, cytotoxic, enzymatic, anti-inflammatory and photosynthetic inhibitory activities have been summarized, paying particular attention on the compounds that have demonstrated antimicrobial properties via inhibition of quorum sensing and biofilm formation

Imidazole-Fused Enediynes by Selective C5–C4 Alkynylations of 4,5-Dibromoimidazoles

An efficient synthesis of symmetrical 1,2-disubstituted 4,5-dialkynylimidazoles by Sonogashira alkynylation of the corresponding 4,5-dibromo derivatives was developed. Moreover, through a careful tuning of the palladium ligand, unsymmetrical 1,2-disusbtituted 4,5-dialkynylimidazoles were also prepared through a regioselective C5 alkynylation of 4,5-dibromoimidazoles, followed by a second alkynylation involving the 4-bromo derivatives so obtained. This interesting class of imidazole-fused enediynes is also able to give thermal Bergman cycloaromatization (BC), as proved by DSC experiments

Vascular Disrupting Activity of Tubulin-Binding 1,5-Diaryl-1H-imidazoles

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“N-alkyl diketopyrrolopyrrole-based fluorophores for luminescent solar concentrators: effect of the alkyl chain on dye efficiency”

We report on the preparation of luminescent solar concentrators (LSCs) made of poly(methyl methacrylate) (PMMA) thin films doped with six new diketopyrrolopyrrole (DPP) fluorophores obtained in good yields by using simple N-alkylation and direct C-H arylation synthetic strategies. Spectroscopic investigations in solution and in PMMA thin films combined with photocurrent measurements revealed that the branched alkyl chains were efficient in preventing DPP segregation from the PMMA matrix thanks to their higher steric hindrance. The aromatic substituent was found to expand DPP conjugation but favoured DPP adverse aggregation, thus affecting fluorescence emission and photocurrents of PMMA films. The worthwhile combination of the appropriate alkyl chain and aromatic moieties assured to achieve optical efficiency of 6.8% that was comparable to that of PMMA LSCs of the state-of-the art (7.2%)

Tuning of dye optical properties by environmental effects: a QM/MM and experimental study

The present work is aimed to a deeper investigation of two recently synthesized heteroaromatic fluorophores by means of a computational multilayer approach, integrating quantum mechanics (QM) and molecular mechanics (MM). In particular, dispersion of the title dyes in a polymer matrix is studied in connection with potential applications as photoactive species in luminescent solar concentrators (LSCs). Molecular dynamics simulations, based on accurate QM-derived force fields, reveal increased stiffness of these organic dyes when going from CHCl3 solution to polymer matrix. QM/MM computations of UV spectra for snapshots extracted from MD simulations show that this different flexibility permits to explain the different spectral shapes obtained experimentally for the two different environments. Moreover, the general spectroscopic trends are well reproduced by static computations employing a polarizable continuum description of environmental effects