Synthesis of 4‐Alkenylated Pyrazolinones by 2,3‐Dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ)‐Mediated Oxidative Coupling Reaction

Abstract

1,3‐Diarylpropenes firstly serve as efficient alkenylated reagents for the functionalization of pyrazolinones. In the presence of 2,3‐Dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ), it undergoes oxidative coupling and final dehydrogenation to give the highly substituted E,E‐α,β,γ,δ‐dienpyrazolinones in moderate to excellent yields.

Tandem Oxidative Reaction of 1,3-Diarylpropenes and 5-Aminopyrazoles

“…11 Our group has developed a DDQ-mediated oxidative coupling/dehydrogenation reaction of pyrazolinones with 1,3-diarylpropenes which gives more stable (E,E)-,:,-alkadienylpyrazolinones, but not the expected cyclization products. 12 Based on this work, and with our interest in the synthesis of heterocycles, herein, we report a tandem oxidative reaction of 5-aminopyrazoles with 1,3-diarylpropenes to give pyrazolo [3,4-b]pyridines (Scheme 1; this work). It involves an oxidative coupling mediated by DDQ and a subsequent intramolecular cyclization and dehydroaromatization in the presence of Cu(OTf) 2 and TBHP.…”

“…No obvious electronic or steric effects were observed. Aminopyrazoles 1k-n containing an alkyl group at the 3-position gave the products 3k-n in yields of 42-75% (entries [11][12][13][14]. The yield decreased with increasing bulk of the alkyl group.…”

“…11 Our group has developed DDQ-mediated oxidative coupling/dehydrogenation reaction of pyrazolinones and 1,3-diarylpropenes, which gives more stable E,E-α,β,γ,δ-dienpyrazolinones, but not the expected cyclization products. 12 Based on this work and with our interest in the synthesis of heterocycles, herein, we will report a tandem oxidative reaction of 5-aminopyrazoles and 1,3-diarylpropenes,…”