Polytetrahydrofuran-Grafted Polystyrene Resin Supports for Organic Synthesis

Significance

Polytetrahydrofuran-grafted polystyrene (PS-PTHF) resins 1 were prepared from 5-hydroxypentyl JandaJel by cationic polymerization using trifluoroacetic anhydride as an initiator. These PS-PTHF resins exhibited good swelling characteristics both at room temperature and at -78 ºC. PS-PTHF was used for the synthesis of 3-methyl-1-phenyl-2-pyrazolin-5-one (5). Thus, resin 1b reacted with acetic acid applying 1,3-diisopropylcarbodiimide (DIC) as a condensation ­reagent to afford 2, which reacted further with LiHMDS, and after treatment with acetyl chloride gave β-ketoester 3. Treatment of 3 with phenylhydrazine afforded 4, which was cleaved with TFA to form 5 in 47% (96% purity). On the other hand, TentaGel (PS-PEG) was shown to be ineffective in this synthesis.