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Synthesis of Strained Tricyclic β‐Lactams by Intramolecular [2+2] Cycloaddition Reactions of 2‐Azetidinone‐Tethered Enallenols: Control of Regioselectivity by Selective Alkene Substitution
Author(s) -
Alcaide Benito,
Almendros Pedro,
Aragoncillo Cristina,
Redondo María C.,
Torres M. Rosario
Publication year - 2006
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.200500807
Subject(s) - cycloaddition , regioselectivity , intramolecular force , chemistry , alkene , allene , stereochemistry , ring (chemistry) , combinatorial chemistry , organic chemistry , catalysis
A convenient metal‐free methodology for the preparation of structurally novel, strained tricyclic β‐lactams containing a cyclobutane ring has been developed. The first examples accounting for the intramolecular [2+2] cycloaddition reactions in β‐lactams have been achieved by the thermolysis of 2‐azetidinone‐tethered enallenols, which have been prepared in aqueous media by regio‐ and diastereoselective indium‐mediated carbonyl allenylation of 4‐oxoazetidine‐2‐carbaldehydes. Notably, the regioselectivity of the cycloaddition can be tuned in the allene component just by a subtle variation in the substitution pattern of the alkene component.