[2+2] Cycloaddition Reactions of Imines with Cyclic Ketenes: Synthesis of 1,3-Thiazolidine Derived Spiro-β-lactams and Their Transformations

✍ Scribed by Giuseppe Cremonesi; Piero Dalla Croce; Concetta La Rosa

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: German
• Weight: 190 KB
• Volume: 88
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.200590125

✦ Synopsis

Abstract

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.