Abstract
The easily available diethyl ethynylphosphonate reacts with diverse aldonitrones under Kinugasa reaction conditions at room temperature, providing 3-phosphonylated beta-lactams in good yields. In all cases, the reaction led to the trans-isomer exclusively. The trans-configuration was assigned based on 1H-NMR spectroscopic analysis.
Highlights
The importance of modified β‐lactams is well documented
3‐Phosphonylated β‐lactams have never been prepared via Kinugasa reactions starting with diethyl ethynylphosphonate (4)
In a recent publication we described a new approach to the synthesis of fluorinated β‐lactams via Kinugasa reactions with fluorinated nitrones and diverse monosubstituted acetylenes, including methyl propiolate.[21]
Summary
The importance of modified β‐lactams is well documented. They are known as important drugs with antimicrobial activity[2] and as inhibitors of cholesterol absorption[3] and thrombin,[4] as well as antitumor[5] and anti‐HIV agents.[6]. There are different methods known for the preparation of 4‐phosphonylated β‐lactams,[9,10,11] including the recently reported Kinugasa approach.[12] In the latter case, the C‐phosphonylated N‐methyl nitrone 1 was reacted with mono‐substituted acetylenes 2 yielding azetidin‐2‐ones 3 as mixtures of cis/trans‐isomers (Scheme 1). Kinugasa reaction with a phosphonylated nitrone leading to 4‐phosphonylated β‐lactams.12
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