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Cycloaddition reactions of N ‐ p ‐toluenesulfonylimino derivatives of quinoline and isoquinoline. A route to pyrazolo[1,5‐ a ]quinolines and pyrazolo[5,1‐ a ]isoquinolines
Author(s) -
Sundberg Richard J.,
Ellis James E.
Publication year - 1982
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570190324
Subject(s) - chemistry , isoquinoline , cycloaddition , quinoline , phenylacetylene , medicinal chemistry , electrophile , 1,3 dipolar cycloaddition , adduct , organic chemistry , stereochemistry , catalysis
N ‐ p ‐Toluenesulfonylimino ylides of quinoline and isoquinoline give cycloadducts with electrophilic acetylenes at 105°. The adducts are spontaneously aromatized under the conditions of their formation by elimination of p ‐toluenesulfmic acid to give pyrazolo[1,5‐ a ]quinolines and pyrazolo[5,1‐ a ]isoquinolines, respectively. The orientation of cycloaddition is the same as for N ‐amino ylides for acetylenic esters. The ad‐ducts from p ‐nitrophenylacetylene are formed by addition of the imino nitrogen to the unsubstituted acetylenic carbon. The orientation and unreactivity of phenylacetylene indicate that the cycloaddition is controlled by dipole HOMO‐dipolarophile LUMO interactions.