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Ring transformations of heterocyclic compounds. XVIII . Spiro[cyclohexadiene-indolines] with three stereocenters from pyrylium salts and chiral methyleneindolines — an example of a high diastereoselective ring transformation

✍ Scribed by Thomas Zimmermann; Ulrich Abram

Publisher
Journal of Heterocyclic Chemistry
Year
1999
Tongue
English
Weight
540 KB
Volume
36
Category
Article
ISSN
0022-152X

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✦ Synopsis

Abstract

The diastereoselective synthesis of 6‐aroyl‐3,5‐diarylspiro[cyclohexa‐2,4‐diene‐1,2′‐indolines] 4 possessing three stereocenters from 2,4,6‐triarylpyrylium perchlorates 1 and chiral methyleneindolines 3 (generated in situ by deprotonation of the corresponding 3__H__‐indolium perchlorates 2) in the presence of triethylamine/acetic acid in ethanol by a 2,5‐[C~4~+C~2~] pyrylium ring transformation is reported. Structure elucidation is performed by X‐ray structure determinations of the spiro[cyclohexadiene‐indolines] 4a, 4p and 4t. The influence of various substituents at C‐3 of the methyleneindolines 3 on the stereochemistry of the transformation, mechanistic details as well as spectroscopic data of the products 4 are discussed.

📜 SIMILAR VOLUMES

Ring transformations of heterocyclic com
Ring transformations of heterocyclic compounds. XVI. Spiro[cyclohexadiene-dihydroacridines]. A novel class of spirodihydroacridines by ring transformation of pyrylium salts with 9-methylacridine and its quaternary salts
✍ Thomas Zimmermann; Ulrich Abram; Klaus Schmidt 📂 Article 📅 1998 🏛 Journal of Heterocyclic Chemistry 🌐 English ⚖ 501 KB

## Abstract 2,4,6‐Triarylpyrylium salts 1 react with the __in situ__ generated anhydrobase of 9,10‐dimethylacridinium methosulfate (2a) in the presence of anhydrous sodium acetate in ethanol by a 2,5‐[C~4~+C~2~] pyrylium ring transformation to give the hitherto unknown 6‐aroyl‐3,5‐diaryl‐10′‐methyl