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Enantioselective Formation of 2‐Azetidinones by Ring‐Assisted Cyclization of Interlocked N ‐(α‐Methyl)benzyl Fumaramides
Author(s) -
MartinezCuezva Alberto,
Bautista Delia,
Alajarin Mateo,
Berna Jose
Publication year - 2018
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201803187
Subject(s) - chemistry , intramolecular force , carbon atom , stereochemistry , enantioselective synthesis , ring (chemistry) , catalysis , organic chemistry
The synthesis of optically active interlocked and non‐interlocked 2‐azetidinones by intramolecular cyclization of N ‐(α‐methyl)benzyl fumaramide [2]rotaxanes is described. Two different strategies of asymmetric induction were tested in which the chiral group was located either proximal or distal to the reacting center of the thread. During these experiments, an interesting equilibration process inside the macrocyclic void occurred, thus leading to the cyclization through the (α‐methyl)benzyl carbon atom and giving rise to β ‐lactams, with a quaternary carbon atom, in an enantio‐ and diastereocontrolled manner. This cyclization also proceeds in kinetically stable chiral pseudo[2]rotaxanes, thus allowing further dethreading to provide enantioenriched 3,4‐disubstituted trans ‐2‐azetidinones. The stereochemical outcomes of the cyclizations inside and outside the macrocycle demonstrated noticeable differences.