Ring transformations of heterocyclic compounds. XXI. Diastereoselective built-up of an aroylcyclohexadiene moiety as second spiro-connected ring at spiroindolines by pyrylium ring transformation

✍ Scribed by Thomas Zimmermann

• Publisher: Journal of Heterocyclic Chemistry
• Year: 2002
• Tongue: English
• Weight: 82 KB
• Volume: 39
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570390202

✦ Synopsis

Abstract

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.