Pyrolysis of 1-alkylazetidinone derivatives: A versatile route toward electron-rich alkenes, C-1 allylation and/or homologation of aldehydes

- β-Lactam pyrolysis as a route to electron rich Z-alkenes and 4-pentenal.
- Routes to convert aldehydes to aryloxyalkenes (a protected homologation).
- Routes to convert aldehydes to 4-pentenal (a C-1 allylation and homologation).

1-Alkyl-3-phenoxy-β-lactams have been synthesized by the standard Staudinger ketene-imine [2+2] cycloaddition. The corresponding β-thiolactams have readily been obtained in good yields by thiation with Lawesson's reagent. Static pyrolysis (STP) as well as FVP of these β-lactams and β-thiolactams led essentially to stereoselective synthesis of Z-alkenes. The 3-allyloxy-1-alkyl-β-lactams and β-thiolactams have also been prepared and gave upon pyrolysis 4-pentenal derivatives. Pyrolysis of 1-alkyl-β-lactams offers better yield than those reported from the corresponding 1-aryl derivatives, it also provides an easy access to the high energy electron-rich Z-alkenes and the synthetically important 4-pentenal.

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