Abstract
AbastractWe developed an efficient one-pot metal-free click polymerization procedure for the synthesis of 3,5-disubstituted polypyrazoles with high yields, high molecular weights, and narrow molecular weight distribution. The method involved two click reactions in a one-pot synthesis. The first reaction was the carbonyl chemistry of “non-aldol” type (condensation reaction of aldehydes with p-toluenesulfonylhydrazide), and the second was a click polymerization reaction of diazo compounds with alkynes. The reactions occurred sequentially by adding the reactants step by step. The diazo compound needed for the second click reaction was generated in situ by the first click reaction. The structures of the polypyrazoles were characterized by IR and 1H NMR analyses. And their thermal properties and solubility were also tested.
Highlights
The development of new polymerization reactions for the preparation of heterocyclic polymers is an important area in polymer research
Aggarwal et al succeeded in using the condensation reaction of aldehydes with p-toluenesulfonyl hydrazine and 1,3-dipolar cycloaddition of diazo compounds with alkyne or N-vinylimidazole to prepare pyrazoles in a one-pot process[13,14,15]
Polyisoxazoles were successfully synthesized by click reaction in one-pot manner in our laboratory[20], which benefited from the high efficiency and regioselectivity of click chemistry
Summary
The development of new polymerization reactions for the preparation of heterocyclic polymers is an important area in polymer research. Moore and Mehta have developed a new route to produce polypyrazoles by reacting bis-chlorovinylidene cyanides with diamines[8] They improved the thermostability of polypyrazoles by employing a vinylic nucleophilic substitution reaction[2]. “Click reactions”, first introduced by Sharpless et al in 20019, are chemical transformations with remarkable advantages, including high efficiency, regioselectivity, and atom economy, fast reaction rates, mild reaction conditions, and simple product isolation They have quickly found widespread applications in various research areas[10,11,12]. Two click reactions (carbonyl chemistry of the “non-aldol” type and a 1,3-dipolar cycloaddition reaction)[9] were involved in the one-pot procedure, and no isolation and purification of the in situ generated diazo compounds is needed, which avoids the very cumbersome and lengthy process and the toxicity and potential explosion of diazo compounds. Correspondence and requests for materials should be addressed to www.nature.com/scientificreports/
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