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Asymmetric Synthesis of Diazepino‐β‐lactams by [2 + 2] Cycloaddition of an ‘ Evans ‐ Sjogven ’ Ketene with 1 H ‐1,2‐Diazepines
Author(s) -
Muller Marc,
Bur Daniel,
Tschamber Théophile,
Streith Jacques
Publication year - 1991
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19910740410
Subject(s) - chemistry , ketene , cycloaddition , steric effects , moiety , adduct , stereochemistry , imine , lactam , derivative (finance) , medicinal chemistry , organic chemistry , catalysis , financial economics , economics
The ketene derivative of the chiral oxazolidinone 1 underwent non‐concerted stereo specific [2 + 2] cycloadditions with the ( Z )‐imine moiety of diazepines 2 , leading thereby with good diastereoselection to the trans ‐β‐lactam adducts 3 (major) and 4 (minor). The absolute configuration of the major cycloadduct 3a was determined by an X‐ray analysis. Its formation is discussed in terms of minimisation of steric interaction in the two transition states which give sequencially the zwitterionic intermediates and the final cycloadducts.