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Rhodium‐Katalysierte Isomerisierungen von 2‐Methylidenglutarsäureestern zu Methylglutaconsäureestern
Author(s) -
Weis Claus D.,
Winkler Tammo
Publication year - 1974
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.19740570343
Subject(s) - chemistry , saponification , isomerization , rhodium , enol , catalysis , medicinal chemistry , hydrogen chloride , distillation , organic chemistry
The Rhodium(III)‐catalyzed thermal isomerization of 2‐methylidenglutaric acid esters affords predominantly mixtures of cis/trans ‐2‐methylglutaconic acid esters ( 2, 3 ) which upon slow distillation isomerize completely into the cis ‐esters ( 2 ). Saponification of 2 yields trans ‐2‐methylglutaconic acid ( 5 ). Attempts to prepare the acid chloride of 5 produces 6‐chloro‐5‐methylpyrone‐2 ( 9 ) or 6‐chloro‐3‐methylpyrone‐2 ( 10 ) which react with anilines to N‐substituted derivatives of trans ‐4‐methylglutaconic acid amides ( 11 ). The thermal isomerizations of the respective esters are discussed in terms of 1,5‐hydrogen shifts in their ester enol structures.