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Medium‐Sized Rings versus Macrocycles through Rhodium‐Catalyzed Ring‐Expansion Reactions of Cyclic Acetals
Author(s) -
BallesterosGarrido Rafael,
Rix Diane,
Besnard Céline,
Lacour Jérôme
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201103870
Subject(s) - oxonium ion , oxocarbenium , chemistry , regioselectivity , electrophile , ylide , ring (chemistry) , intramolecular force , catalysis , rhodium , nucleophile , medicinal chemistry , stereochemistry , organic chemistry , ion
α‐Diazo β‐ketoesters and diketones react with cyclic acetals under Rh II catalysis to yield unprecedented polyoxygenated 8‐ and 9‐membered rings in one pot. The reactions occur under mild conditions with yields up to 90 %. A perfect regioselectivity is obtained, which can be rationalized through a mechanistic hypothesis that considers 1) the formation of an oxonium ylide, 2) its transformation into an unsaturated acyclic oxocarbenium electrophilic intermediate, and 3) an intramolecular nucleophilic attack in a direct application of Baldwin’s rules.