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Updated: Sep 29, 2026

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
Published on: February 7, 2019
A convenient synthetic method of a 5,7-diarylcyclopenteno-[1,2-b]pyridine-6-carboxylate: a key intermediate for
Kenji Niiyama1, Takashi Yoshizumi, Hirobumi Takahashi
1Tsukuba Research Institute, Banyu Pharmaceutical Co., Ltd., 3 Okubo, Tsukuba, Ibaraki, Japan. niiymakj@banyu.co.jp
Abstract:
A convenient method for the synthesis of the title intermediate 4 was described. The key steps of this synthesis involved: (1) regioselective addition reaction of arylzinc reagent to quinolic anhydride in 42% isolated yield, (2) conversion of a ketoacid to an enone, which was achieved in 65% yield by intramolecular Knoevenagel reaction of beta-ketoester generated by condensation of an acid imidazolide with an ester enolate, followed by dehydration assisted with silica gel, and (3) stereoselective reduction of an allyl alcohol in 75% yield with zinc under acidic conditions. This synthesis enabled us to provide hundreds of grams of without chromatographic purification.
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