Issue 48, 2015

Synthesis of pyrazolo[5,1-a]isoquinolines via a silver(i)-catalyzed reaction of (1-arylethylidene)hydrazides with N′-(2-alkynylbenzylidene)hydrazides

Abstract

A silver(I)-catalyzed reaction of (1-arylethylidene)hydrazides with N′-(2-alkynylbenzylidene)hydrazides is reported, which provides an efficient approach for the synthesis of pyrazolo[5,1-a]isoquinolines. During the reaction process, azo-alkene and isoquinolinium-2-yl amide acted as the key intermediates, which then underwent [3 + 2] cycloaddition and intramolecular rearrangement leading to the corresponding pyrazolo[5,1-a]isoquinolines. Azo-alkene would be formed in situ from (1-arylethylidene)hydrazide in the presence of I2 and TBHP, and isoquinolinium-2-yl amide would be generated in situ via a silver(I)-promoted 6-endo cyclization of N′-(2-alkynylbenzylidene)hydrazide. This transformation proceeds smoothly under mild conditions and tolerates a broad range of functional groups.

Graphical abstract: Synthesis of pyrazolo[5,1-a]isoquinolines via a silver(i)-catalyzed reaction of (1-arylethylidene)hydrazides with N′-(2-alkynylbenzylidene)hydrazides

Supplementary files

Article information

Article type
Paper
Submitted
22 Sep 2015
Accepted
07 Oct 2015
First published
08 Oct 2015

Org. Biomol. Chem., 2015,13, 11657-11662

Synthesis of pyrazolo[5,1-a]isoquinolines via a silver(I)-catalyzed reaction of (1-arylethylidene)hydrazides with N′-(2-alkynylbenzylidene)hydrazides

X. Gong and J. Wu, Org. Biomol. Chem., 2015, 13, 11657 DOI: 10.1039/C5OB01972A

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