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Ring transformations of heterocyclic compounds. XXI . Diastereoselective built‐up of an aroylcyclohexadiene moiety as second spiro‐connected ring at spiroindolines by pyrylium ring transformation
Author(s) -
Zimmermann Thomas
Publication year - 2002
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.5570390202
Subject(s) - chemistry , ring (chemistry) , moiety , cycloalkene , triethylamine , cycloalkane , stereochemistry , transformation (genetics) , acetic acid , medicinal chemistry , organic chemistry , catalysis , biochemistry , gene
2,4,6‐Triarylpyrylium perchlorates 1 react with methyleneindolines 3 in situ generated from the corresponding methylindolium salts 2 , which are spiro‐fused with a cycloalkane, benzanellated cycloalkene or a heterocyclic system. These diastereoselective 2,5‐[C 4 +C 2 ] pyrylium ring transformations are carried out in the presence of triethylamine/acetic acid in boiling ethanol to give the dispiroindolines 4 with a trans configuration of the more bulky substituents at the cyclohexadiene ring. By the same type of transformation the dispiro compounds 7/10 with an additional fused benzene ring are obtained from the pyrylium salt 1a and 6/9 , the benzo‐fused analogues of 3 . Spectroscopic data of the transformation products as well as their mode of formation are discussed.