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Benzylidène‐5‐hydroxy‐4‐dihydro‐2,5‐thiophènecarboxanilides‐3‐( Z ): Synthèse et isomérisation en benzyl‐5‐hydroxy‐4‐thiophènecarboxanilides‐3
Author(s) -
Jaunin Roland
Publication year - 1980
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.19800630623
Subject(s) - chemistry , isomerization , thiophene , yield (engineering) , medicinal chemistry , xylene , boiling , stereochemistry , catalysis , organic chemistry , toluene , materials science , metallurgy
( Z )‐5‐Benzylidene‐2,5‐dihydro‐4‐hydroxy‐3‐thiophenecarboxanilides: Synthesis and Isomerization into 5‐Benzyl‐4‐hydroxy‐3‐thiophenecarboxanilides Upon treatment with an arylamine in boiling xylene, the esters I yield predominantly the corresponding anilides II, along with a small but variable amount of the isomeric thiophene derivatives III ( Table 1 ). On the other hand, the derivatives III can be readily prepared by base‐ or acid‐catalyzed isomerization of II . Esters I can also be isomerized to the corresponding thiophene derivatives IV (Scheme 6) , but only in the presence of a strong acid (Table 4) . The two series of isomers reported in Tables 2 and 3 present spectral differences which allow unambiguous structural assignments. The ( Z )‐configuration for compounds of Table 2 is confirmed by a NOE study carried out on the O ‐methyl derivatives 6a and 7a .