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[2+3] Cycloadditions of Azomethine Ylides with 1,3‐Thiazole‐5(4 H )‐thiones
Author(s) -
Mlostoń Grzegorz,
Linden Anthony,
Heimgartner Heinz
Publication year - 1998
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.19980810309
Subject(s) - chemistry , azomethine ylide , stereoselectivity , thiazole , isomerization , aziridine , ylide , cycloaddition , medicinal chemistry , electrocyclic reaction , ring (chemistry) , toluene , stereochemistry , 1,3 dipolar cycloaddition , organic chemistry , bicyclic molecule , catalysis
Thermal reactions of 1,2,3‐trisubstituted aziridines 1 with 1,3‐thiazole‐5(4 H )‐thiones 6 in toluene yielded, in general, a mixture of two diastereoisomeric spirocyclic [2+3] cycloadducts. The formation of these products can be explained by a stereoselective electrocyclic ring opening of 1 to give an azomethine ylide 2 as the reactive intermediate, which is trapped immediately by 6 via a stereoselective 1,3‐dipolar cycloaddition. Only in the case of trans ‐dimethyl 1‐(4‐methoxyphenyl)aziridine‐2,3‐dicarboxylate ( trans ‐ 1a ), four diastereoisomeric cycloadducts were formed ( Scheme 4 ). This result is rationalized by an isomerization of the intermediate azomethine ylide cis ‐ 2a to trans ‐ 2a .