Studies on the Generation of Metalating Species Equivalent to the Knochel–Hauser Base in the Dehydrobrominative Polymerization of Thiophene Derivatives

Abstract

Dehydrobrominative polycondensation of 2-bromo-3-hexylthiophene proceeded with TMPMgBr•LiBr and (TMP) 2 Mg•2LiBr, formed by LiTMP and MgBr 2 , which was found to serve as a surrogate of the Knochel−Hauser base TMPMgCl•LiCl, and head-to-tail-type regioregular poly(3-hexylthiophene) was obtained with high efficiency. The regioregular poly(3-hexylthiophene) was also found to be obtained by one-shot addition of 2-bromo-3-hexylthiophene as a monomer, magnesium amide, and a nickel catalyst, suggesting that complete formation of metalated thiophene species is not an essential requisite for the successful polymerization with a nickel catalyst. This method was employed for the preparation of tolylterminated polythiophene by an aryl group with narrow molecular weight distribution using (o-tolyl)NiCldppp as a catalyst.

Dehalogenative or Deprotonative? The Preparation Pathway to the Organometallic Monomer for Transition‐Metal‐Catalyzed Catalyst‐Transfer‐Type Polymerization of Thiophene Derivatives

“…The obtained solution of the Knochel–Hauser base can be stored as a THF solution. The related deprotonating reagent was found to be prepared by the reaction of LiTMP and MgBr 2 , which allowed several deprotonative metalation species with different ratios of Mg/nitrogen, as summarized in Scheme . Deprotonation with TMPMgCl, TMP 2 Mg, and TMP 3 Mg − Li + was revealed to take place, with which all of such reagents were available for the deprotonative metalation and thus obtained metalated thiophene allowed for polymerization catalyzed by nickel(II).…”

Recent developments in the synthesis of regioregular thiophene-based conjugated polymers for electronic and optoelectronic applications using nickel and palladium-based catalytic systems

“…170,[172][173][174] Employment of 2-halo-3-substituted thiophenes instead of 2,5-dihalothiophenes along with the Knochel-Hauser 167,175 base have been the key for the successful synthesis of thiophenebased polymers. 170,[176][177][178][179][180][181][182] Magnesium amide does not interfere with the propagation of the polymer during the course of the reaction. 164 Dehydrobrominative polycondensation proceeds with the higher atom efficiency compared to the dehalogenative polycondensation employing Grignard reagent.…”

Modern Developments in Magnesium Reagent Chemistry for Synthesis

“…The more complex thienothiophene subunit, which boasts applications in materials chemistry due to its conjugated  system, can also be magnesiated directly with Turbo-A, while this protocol can be applied for the preparation of linear oligomeric thienothiophene molecules (Figure 14) [35]. Mori has also recently used Turbo-A as well as the bromo congeners (TMP)MgBr•LiBr and (TMP)2Mg•2LiBr as selective deprotonating agents with substituted thiophenes to efficiently prepare well-defined head-to-tail oligomers [36][37]. The synthetic utility of reagent A has also been exploited by Maes and coworkers, who have studied its reaction with pyridazin-3(2H)-ones (Figure 15) [38].…”