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[2+2] Cycloaddition Reactions of Imines with Cyclic Ketenes: Synthesis of 1,3‐Thiazolidine Derived Spiro‐ β ‐lactams and Their Transformations
Author(s) -
Cremonesi Giuseppe,
Dalla Croce Piero,
La Rosa Concetta
Publication year - 2005
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.200590125
Subject(s) - chemistry , thiazolidine , cycloaddition , ketene , ring (chemistry) , reagent , staudinger reaction , imine , stereoselectivity , lactam , stereochemistry , medicinal chemistry , organic chemistry , catalysis
Unsymmetric cyclic ketenes were generated from N ‐acyl‐1,3‐thiazolidine‐2‐carboxylic acids 1a – c by means of Mukaiyama 's reagent, and then reacted with imines 2a – c to the new, isomeric spiro‐ β ‐lactams 3 and 4 via [2+2] cycloaddition ( Staudinger ketene–imine reaction; Scheme 1 ). The reactions were stereoselective ( Table 1 ) and mainly afforded the spiro‐ β ‐lactams with a relative trans configuration. The spiro‐ β ‐lactams could be transformed into the corresponding monocyclic β ‐lactams by means of thiazolidine ring opening or into substituted thiazolidines via hydrolysis of the β ‐lactam ring.