Pyrolysis of b-lactams and b-thiolactams led essentially to stereoselective synthesis of the high energy electron-rich Z-alkenes. Extension of this methodology to the pyrolysis of 3-allyloxy derivatives gave a simple direct route to the synthetically important 4-pentenal. These pyrolytic transformations convert aldehydes to aryloxyalkenes (a protected homologation) and 4-pentenal (a C-1 allylation and homologation). The starting 3-aryloxy and 3-allyloxy-b-lactams were synthesized by the standard

Alkenes, C-1 Allylation and/or Homologation of Aldehydes. -Azetidinone and azetidinthione derivatives are transformed into valuable intermediates including electron-rich Z-olefins (III) and 4-pentenal derivatives [e.g. (VII)]. -(AL-HAMDAN, N. S.; HABIB, O. M.; IBRAHIM, Y. A.; AL-AWADI*, N. A.; EL-DUSOUQUI, O. M. E.; RSC Adv. 4 (2014) 40, 21023-21031, http://dx.

The kinetics of the gas-phase thermolysis reaction of seven β-lactams and their thione analogues were investigated over the temperature range 533–603 K for the β-lactams and 463–542 K for the β-thiolactams. The average values of the energy of activation (Ea) (kJ mol−1) and Arrhenius log A (s–1) were, respectively, 170.8 ± 18.6 and 12.4 ± 1.6 for the lactams and 131.7 ± 18.2 and 11.0 ± 2.0 for the thione analogues. The entropy of activation (ΔS#) was negative for of the substrates and slightly positive for three. The rate constants (k) (s−1) were calculated for 510 K and compared for the two series of azetidinones. The effects of substituents on rates and the novel role played by the C=O and C=S moieties on the relative reactivities of the cyclic amides are rationalized on the basis of a formal retro[2+2]cycloaddition mechanism used earlier to explain the products of the gas-phase thermolysis reaction of the present azetidinones.