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Synlett 2011(7): 964-968  
DOI: 10.1055/s-0030-1259704
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© Georg Thieme Verlag Stuttgart ˙ New York

Rapid Access to H-Pyrazolo[5,1-a]isoquinolines via Sequential Reaction of N′-(2-Alkynylbenzylidene)hydrazides

Zhiyuan Chena, Xiaolin Pana, Jie Wu*a,b
a Department of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433, P. R. of China
Fax: +86(21)65641740; e-Mail: jie_wu@fudan.edu.cn;
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, P. R. of China
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Publication History

Received 1 October 2010
Publication Date:
08 March 2011 (online)

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Abstract

Diverse H-pyrazolo[5,1-a]isoquinolines are efficiently synthesized via sequential reaction of N′-(2-alkynylbenzylidene)hydrazides. Bromo-containing isoquinolinium, generated from N′-(2-alkynylbenzylidene)hydrazide with bromine, reacts with α,β-unsaturated aldehyde and methanol under mild conditions, leading to 6-bromo-1-(methoxymethyl)-H-pyrazolo[5,1-a]isoquinolines in moderate to good yields. Further elaboration via palladium catalyzed Suzuki-Miyaura coupling or Heck reaction produces diverse H-pyrazolo[5,1-a]isoquinoline compounds.

Key words

alkynes - hydrazide - bromine - methanol - isoquinoline - α,β-unsaturated aldehyde