A route to benzodithiophene systems by exploiting a ligand-free Suzuki-Miyaura coupling reaction in deep eutectic solvents

Benzo[1,2-b:4,3-b\u2019]dithiophene (BDT) and its derivatives belong to an interesting class of thiophene-based aromatic \uf070-conjugated compounds that are widely studied as functional organic materials inserted, for instance, as units in mono and polydisperse oligomers [1], or as \uf070-spacers in push-pull organic chromophores for photovoltaic applications [2]. Moreover, BDTs are key intermediates for the synthesis of inherent chiral tetrathia[7]helicenes, which are an attractive class of heterohelicenes with unique physicochemical and chiroptical properties due to their helix-like structure [3]. Thus, BDT is a key starting molecule which can allow access to more complex and interesting systems through a selective and judicious functionalization of the \uf061 and \uf062-positions of the terminal thiophene rings. Building on our recent studies on the synthesis and functionalization of BDTs [4], we questioned whether a novel class of 2,7-diarylsubstituted BDTs 1 (Figure 1) could be synthesized via a palladium-catalysed Suzuki-Miyaura reaction between heteroaryl halides 2 and organoboron derivatives 3 in Deep Eutectic Solvents (DESs), which have proven to be effective as sustainable and environmentally responsible reaction media in several transition-metal-catalyzed reactions [5].In this communication, we report our preliminary results on the preparation of diarylsubstituted BDTs 1, and discuss the substrate scope of the proposed protocol. Some of the compounds so far obtained display interesting photophysical properties, which are currently under investigation

Ligand-Free Cobalt-Catalyzed Cross-Coupling Reaction Between Organoaluminum Reagents and (Hetero)Aryl and Alkyl Bromides

Transition-metal catalyzed cross-coupling reactions are some of the most important C−C bond-forming protocols and have been widely applied both in academic research and in industry. Since the discovery of cross-coupling reactions in the early 1970’s, a great number of catalytic systems using organoboron, organotin, organosilicon, organozinc or organozirconium, and organomagnesium as coupling reagents have been developed. In contrast, coupling reactions employing organoaluminum reagents are very rare. These reagents exhibited high chemoselectivity and good compatibility of functional groups in C−C bond formation reactions. Moreover, aluminum exhibits low toxicity and is one of the most inexpensive and earth-abundant metals. As part of our current research interest in developing new catalytic synthetic methodologies, in this communication we report a very general, cobalt catalyzed cross coupling reaction between alkyland aryl-aluminum compounds with alkyl- and (hetero)aryl bromides, affording the C(sp2)−C(sp2) and C(sp3)−C(sp2) cross-coupled products in good to excellent yields. Catalyzed by the cheap and commercially available CoCl2, without external ligands or bases, the reactions proceed smoothly with a wide range of substituted bromides, decorated by electrodonating and electro-withdrawing group, providing a versatile methodology for cobalt-mediated cross-coupling processes

Cobalt-catalyzed cross-coupling reactions of aryl- And alkylaluminum derivatives with (hetero)aryl and alkyl bromides

A simple cobalt complex, such as Co(phen)Cl2, turned out to be a highly efficient and cheap precatalyst for a host of cross-coupling reactions involving aromatic and aliphatic organoaluminum reagents with aryl, heteroaryl and alkyl bromides. New C(sp2)-C(sp2) and C(sp2)-C(sp3) bonds were formed in good to excellent yields and with high chemoselectivity, under mild reaction conditions

Reazioni Mediate e Catalizzate Da Metalli In Solventi Non Convenzionali: Aspetti Sintetici e Meccanicistici

Green chemistry integrates environmentally safe and sustainable technologies for chemical research and production. Classical synthetic protocols, even with widespread applicability, have various drawbacks due to the use of harsh conditions, long reaction times, and the generation of large amounts of waste. Over the past few years, our research group has been focusing on the development of methodologies with a low ecological footprint using the so-called Deep Eutectic Solvents (DESs) and water as environmentally responsible reaction media and catalysts, thereby reshaping several organic transformations, which are traditionally carried out using toxic and often harmful petroleum-based volatile organic compounds. In this context, metal-mediated and metal-catalysed organic reactions have been successfully accomplished in the aforementioned reaction media under mild conditions and under airLa chimica verde comprende tecnologie sostenibili e sicure per l’ambiente, la ricerca e la produzione chimica industriale. I protocolli sintetici classici, presentano vari inconvenienti dovuti all’uso di condizioni di reazione drastiche, tempi lunghi e produzione di grandi quantità di rifiuti. Negli ultimi anni, il nostro gruppo di ricerca si è concentrato sullo sviluppo di metodologie a basso impatto ambientale, basate sull’utilizzo di acqua o miscele eutettiche a basso punto di fusione sia come mezzi di reazione che come catalizzatori. In questo contesto, reazioni organiche mediate e catalizzate da metalli sono state realizzate con successo nei suddetti mezzi in condizioni blande, all’aria e in tempi brev

Sustainable Ligand-Free Heterogeneous Palladium-Catalyzed Sonogashira Cross-Coupling Reaction in Deep Eutectic Solvents

The commercially available and cheap Pd/C was found to promote Sonogashira couplings in the environmentally friendly choline chloride/glycerol eutectic mixture in the absence of external ligands. Under heterogeneous conditions, (hetero)aryl iodides were successfully coupled with both aromatic and aliphatic alkynes in yields ranging from 50 to 99 % within 3 h at 60 °C. The aforementioned catalytic system proved to be effective also towards electron-rich iodides, which are notoriously known to be poorly reactive in Pd-catalyzed Sonogashira coupling reactions. The eutectic mixture and the catalyst could easily and successfully be recycled up to four times with an E-factor as low as 24.4

Sustainable Ligand-Free Heterogeneous Palladium-Catalyzed Sonogashira Cross-Coupling Reaction in Deep Eutectic Solvents

The commercially available and cheap Pd/C was found to promote Sonogashira couplings in the environmentally friendly choline chloride/glycerol eutectic mixture in the absence of external ligands. Under heterogeneous conditions, (hetero)aryl iodides were successfully coupled with both aromatic and aliphatic alkynes in yields ranging from 50 to 99 % within 3 h at 60 °C. The aforementioned catalytic system proved to be effective also towards electron-rich iodides, which are notoriously known to be poorly reactive in Pd-catalyzed Sonogashira coupling reactions. The eutectic mixture and the catalyst could easily and successfully be recycled up to four times with an E-factor as low as 24.4

Synthesis of benzodithiophene systems by a ligand-free Suzuki-Miyaura coupling reaction in Deep Eutectic Solvents

Benzo[1,2-b:4,3-b\u2019]dithiophene (BDT) and its derivatives belong to an interesting class of thiophene-based aromatic \u3c0-conjugated compounds that are widely studied as functional organic materials inserted, for instance, as units in mono and polydisperse oligomers, or as \u3c0-spacers in push-pull organic chromophores for photovoltaic applications1. Moreover, BDTs are key intermediates for the synthesis of inherent chiral tetrathia[7]helicenes, which are an attractive class of heterohelicenes with unique physicochemical and chiroptical properties due to their helix-like structure2. Thus, BDT is a key starting molecule which can allow access to more complex and interesting systems through a selective and judicious functionalization of the \u3b1 and \u3b2-positions of the terminal thiophene rings. Building on our recent studies on the synthesis and functionalization of BDTs3, we questioned whether a novel class of 2,7-diarylsubstituted BDTs 1 (Figure 1) could be synthesized via a palladium-catalysed Suzuki-Miyaura reaction between heteroaryl halides 2 and organoboron derivatives 3 in Deep Eutectic Solvents (DESs), which have proven to be effective as sustainable and environmentally responsible reaction media in several transition-metal-catalyzed reactions4. In this communication, we report our preliminary results on the preparation of diarylsubstituted BDTs 1, and discuss the substrate scope of the proposed protocol. Some of the compounds so far obtained display interesting photophysical properties, which are currently under investigation

Directed ortho-metalation–nucleophilic acyl substitution strategies in deep eutectic solvents: the organolithium base dictates the chemoselectivity

Directed ortho metalation (DoM) or nucleophilic acyl substitution (SNAc) can be efficiently programmed on the same aromatic carboxylic acid amide, in a choline chloride-based eutectic mixture, by simply switching the nature of the organolithium reagent. Telescoped, one-pot ortho-lithiation/Suzuki-Miyaura cross-couplings have also been demonstrated for the first time in Deep Eutectic Solvents