Cross-Coupling Polymerization of Organosodium for Polythiophene Synthesis

概要

Treatment of 2-chloro-3-hexylthiophene with sodium 2,2,6,6-tetramethylpiperidin-1-yl (TMPNa) in hexane resulted in deprotonation at the 5-position to afford the thiophene-sodium species, whose formation was confirmed by quenching with iodine, leading to 2-chloro-3-hexyl-5-iodothiophene in 85% yield. Addition of a nickel catalyst bearing an N-heterocyclic carbene (NHC) to the thus-formed thiophene-sodium species in cyclopentyl methyl ether induced a cross-coupling polymerization at −20 °C. After the reaction mixture was stirred for 24 h, poly(3-hexylthiophen-2,5-diyl) was obtained in 56% yield. The average molecular weight M-n was revealed to be 9700, which was close to the theoretical molecular weight (M = 8500) on the basis of the monomer feed/catalyst loading ratio (2.0 mol %), and the molecular weight distribution was found to be 2.1.

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