A New Poly(3-alkylthiophene) Synthesis via Pd-Catalyzed Coupling of Thienyl Mercuric Chlorides

Abstract

A new coupling reaction based on the Pd-catalyzed reductive coupling of thienyl mercuric chlorides is described. A variety of substituted thiophenes react with HgCl2 to produce thienyl mercuric chlorides. The degree of substitution can be controlled by the choice of temperature, solvent, and reaction time, and the resulting chloromercuri thiophenes or bis(chloromercuri)thiophenes are stable to air and water. Heating the thienyl mercuric chlorides in pyridine solvent with Cu powder and PdCl2 catalyst gave good yields of the coupled thiophenes. Poly(alkyl)thiophenes, poly(alkyl thienylacetate esters), and copolymers of alkylthiophenes with unsubstituted thiophene were formed in good yields. Molecular weights, M w, were in the range 5300−83000. This coupling reaction was demonstrated to be compatible with the presence of an electrophilic substituent that is attacked by more nucleophilic intermediates, e.g., thienyllithium or thienyl Grignard reagents. Thus, this synthesis should be compatible with substituents known to be unreactive toward arylmercuric chlorides or arylpalladium compounds and is therefore complementary to the organometallic coupling schemes currently in use.

Oligothiophene Synthesis by a General C–H Activation Mechanism: Electrophilic Concerted Metalation–Deprotonation (eCMD)

“…Oligothiophenes are particularly attractive synthetic targets for oxidative dehydrogenative coupling given their privileged status among conjugated materials with optical, electronic, and packing properties appropriate for organic field effect transistors (OFET), organic light-emitting diodes (OLED), organic photovoltaics (OPV), electrochromic devices (ECD), and liquid crystals . Compared to classic methods, such as the representative cases illustrated in Scheme that require stoichiometric organolithium, hypervalent iodine, or mercury reagents, direct catalytic oxidative dehydrogenative coupling , can construct the C–C linkage of these important conjugated materials in a potentially milder and more sustainable fashion. Existing methods for the latter nevertheless have practical drawbacks, and mechanistic uncertainties about what catalyst and ligand structures can accelerate the key C–H cleavage step hinder progress in this area.…”

Synthesis of Poly(3-alkylthienylene ketone)s by the Pd-Catalyzed Copolymerization of Carbon Monoxide with Thienyl Mercuric Chlorides

“…We have recently reported the adaptation of the Pd-catalyzed coupling of organomercuric chlorides to the synthesis of poly(3-alkylthiophene)s ( PAT s) and poly(3-(carboalkoxymethyl)thiophene)s ( PATA s, eq 1). , This chemical coupling reaction ensures α,α‘ links between the thiophene rings and is compatible with the presence of functional groups on the pendant side chain that are attacked by strongly nucleophilic reagents, e.g., thienyllithium or Grignard reagents. The mechanism that was proposed (Scheme ) for the coupling reaction involves the intermediacy of thienylpalladium compounds.…”

Synthesis, Optical and Electrochemical Properties of High-Quality Cross-Conjugated Aromatic Polyketones

“…There are relatively few reports about novel polymerization methods to prepare cross-conjugated aromatic polyketones. Curtis and co-workers developed the synthesis of cross-conjugated aromatic poly­(3-alkylthiophene)­ketones by a Pd-catalyzed copolymerization of bis­(chloromercury)-thiophenes (highly toxic) with carbon oxides (high pressure) in hot pyridine. − Hudson and co-workers reported the synthesis of aromatic polyketones through an aldol condensation of cyclic ketones with aromatic dialdehydes . However, these aromatic polyketones materials suffered from low solubility because they were partially cross-linked.…”