Reaction of Electron-Deficient N=N, N=O Double Bonds, Singlet Oxygen, and CC Triple Bonds with Acyloxyketenes or Mesoionic 1,3-Dioxolium-4-olates: Generation of Unstable Mesoionic 1,3-Dioxolium-4-olates from Acyloxyketenes

摘要

Reactions of azodicarboxylates and nitrosobenzene derivatives with acyloxyketenes generated from dehydrochlorination of α-acyloxyarylacetyl chlorides were carried out to give triacylbenzamidine and N-arylimide derivatives, respectively, in good yields. The same compounds were obtained from the reaction with mesoionic 1,3-dioxolium-4-olates generated by Rh_2(OAc)_4-catalyzed decomposition of aryldiazoacetic anhydride derivatives. Formation of the same compounds from the different starting materials indicates that their reactions involve the same intermediates. The formation of triacylbenzamidine and N-arylimide derivatives is explained by 1,3-dipolar cycloaddition between electron-deficient N=N or N=O bonds and mesoionic 1,3-dioxolium-4-olates following by decarboxylation, ring opening of the resultant carbonyl ylides, and subsequent Mumm rearrangement of the corresponding imidates. The reaction with singlet oxygen composed of more electronegative atoms than N=N and N=O bonds also gave products arising from the singlet oxygen adducts with 1,3-dioxolium-4-olates. The generation of less stable mesoionic 1,3-dioxolium-4-olates from acyloxyketenes was also confirmed by isolation of furandicarboxylates on generation of acyloxyketenes from α-acyloxyarylacetyl chlorides in the presence of reactive dipolarophile dimethyl acetylenedicarboxylate.