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Recent Advances in Ring Transformations of Five‐Membered Heterocycles and Their Fused Derivatives
Author(s) -
Hajós György,
Riedl Zsuzsanna,
Kollenz Gert
Publication year - 2001
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200109)2001:18<3405::aid-ejoc3405>3.0.co;2-y
Subject(s) - ring (chemistry) , chemistry , heteroatom , reduced ring , transformation (genetics) , primitive ring , chain (unit) , stereochemistry , principal ideal ring , pure mathematics , mathematics , physics , commutative ring , organic chemistry , biochemistry , astronomy , commutative property , gene
Ring transformations of five‐membered heterocycles and their benzologues for the recent 10 years are discussed and reviewed. These transformations are classified into four groups: (a) “classical ring transformations”, where the starting and resulting ring system is of the same size, but the heteroatoms and/or their positions have been changed; (b) “degenerate ring transformations”, where during the course of the transformation the starting compound and product have the same ring system, but the reaction proceeds by a ring opening and subsequent ring closure process; (c) “ring contractions” and “ring enlargements”, where the sizes of the product rings are smaller or larger, respectively, than those of the starting compound; and (d) “pseudo ring transformation” or “ring‐chain transfer”, where the process is formally a ring transformation, but is realised by a ring closure of a side chain of the starting heterocycle and opening of the original ring. Reaction mechanisms of the most interesting ring transformations are also discussed.