Multicomponent Tandem Polymerizations of Aromatic Diynes, Terephthaloyl Chloride, and Hydrazines toward Functional Conjugated Polypyrazoles

Abstract

Multicomponent tandem polymerizations (MCTPs) of alkynes enjoying concise procedure, operational simplicity, synthetic efficiency, large structural diversity, high atom economy, and environmental benefit are recently developed as efficient strategies to synthesize functional conjugated polymers, which have attracted much attention from polymer scientists. In this work, through combination of Sonogashira coupling–Michael addition–cyclocondensation reactions in a one-pot procedure, an efficient three-component tandem polymerization of alkyne, carbonyl chloride, and hydrazine hydrate was reported to proceed smoothly under mild conditions at room temperature, affording polypyrazoles with high molecular weights (M w up to 19 400 g/mol) in excellent yields (up to 95%). This MCTP also applies to various aromatic diynes and aromatic hydrazines, producing polypyrazoles with improved solubility and processability, higher M ws of up to 30 700 g/mol, and high yields. Structural characterization of the polymers such as IR, 1H NMR, and 13C NMR spectra suggested total consumption of monomers and complete conversion of the polymer intermediate, proving the desired well-defined structure of polypyrazoles. These polypyrazoles generally enjoy good solubility and film-forming ability, high thermal stability, high light refractivity, and luminescence behavior. Such MCTPs are not just a simple reaction to connect functional units together in a polymer chain; they can also build functional units such as the newly formed multisubstituted heterocyclics embedded in the polymer main chain at the same time.

Advanced functional polymer materials

“…12, Route 4). 113 Furthermore, the one-pot MCTPs of alkynes, carbonyl chloride, and Fischer's base were developed to afford conjugated poly(diene-merocyanine)s with satisfactory molecular weights (M w up to 10.9 Â 10 3 g mol À1 ) and higher yields (up to 81%) ( Fig. 12, Route 5).…”

Multicomponent Polymerization for π‐Conjugated Polymers

“…A π‐conjugated pyrazole‐based polymer ( 4‐P18 ) was produced in a similar one‐pot procedure (Sonogashira coupling−Michael addition−cyclocondensation) when 2‐mercaptoacetate was replaced with phenylhydrazine. [ 57,58 ] Moreover, when the active polyalkynone ( 4‐P15 ) was treated with Fischer's base as an enamine nucleophile, a π‐cross‐conjugated poly(diene merocyanine) ( 4‐P17 ) was generated via a consecutive addition‐cyclization‐ring opening pathway, as depicted in Figure 15b. [ 59,60 ]…”

Multicomponent Tandem Polymerization of Aromatic Alkynes, Carbonyl Chloride, and Fischer's Base toward Poly(diene merocyanine)s

“…To explore the general applicability of MCPs and their polymerization product structures, a popular tandem strategy in organic synthesis has been introduced to MCPs . The multicomponent tandem polymerizations (MCTPs) were developed to synthesize heteroatom or heterocycles‐containing conjugated polymers or sequence‐controlled polymers with well‐defined structures in one pot . For example, sulfur‐rich conjugated polymers with good stereoselectivity was prepared through the MCTP of alkynes, carbonyl chlorides, and thiols; conjugated polypyrazoles were prepared from the MCTP of alkyne, carbonyl chlorides, and benzohydrazines; polypyrimidines could be obtained from the coupling‐addition‐cyclization‐oxidation four‐step MCTP of alkyne, guanidine hydrochloride, DMSO, and O 2 ; most recently, poly(indolone)s with acid‐triggered fluorescence response property were synthesized through MCTP .…”