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Dérivés C‐glycosyliques VIII . Synthèse de C‐glycosyl‐3‐pyrazoles à partir d'une nitrilimine dérivée de l'anhydro‐2,5‐ D ‐ribose. Compétition entre cyclo‐additions dipolaires‐1,3 et cyclisations non concertés
Author(s) -
Tronchet J. M. J.,
Perret Melle F.
Publication year - 1972
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19720550631
Subject(s) - chemistry , phenylacetylene , bromide , electrophile , nucleophile , medicinal chemistry , glycosyl , pyrazole , stereochemistry , organic chemistry , catalysis
Several 3‐(2,5‐anhydro‐ribosyl)‐pyrazoles of potential medicinal interest have been synthesized by reacting alkynes or alkynylmagnesium bromides with the p ‐nitrophenylhydrazone of 2,5‐anhydro‐ribonyl bromide. From a mechanistic standpoint, it has been shown that the sugar‐nitrilimine used in these studies reacts more readily as an electrophile than as a dipole. Thus, the hydrazonyl bromide gave exclusively the corresponding phenylethynylhydrazone when treated with phenylethynylmagnesium bromide and led to a 1:1 mixture of phenylethynylhydrazone and pyrazole when reacted with phenylacetylene. This proves that nucleophilic additions onto nitrilimines are much faster than Huisgen's 1,3‐dipolar cycloadditions.