Self Cycloaddition of o‐Naphthoquinone Nitrosomethide to (±) Spiro{naphthalene(naphthopyranofurazan)}‐one Oxide: An Insight into its Formation. Issue 12 (8th December 2022)

• Record Type: Journal Article
• Authors: Tzeli, Demeter; Gerontitis, Ioannis E.; Petsalakis, Ioannis D.; Tsoungas, Petros G.; Varvounis, George
• Is Part Of: ChemPlusChem. Volume 87:Issue 12(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-12-08
• Subjects: cycloaddition -- DFT calculations -- oxidation -- oximes -- spiro naphthoquinone; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/cplu.202200313
• Languages: English
• ISSNs: 2192-6506

Abstract

Abstract: 2‐Hydroxy‐1‐naphthaldehyde oxime was oxidized by AgO (or Ag2 O), in presence of N‐methyl morpholine N‐oxide (NMMO), to the title spiro adduct‐dimer (±)‐ Spiro {naphthalene‐1(2 H ), 4′‐(naphtho[2′, 1′:2, 3]pyrano[4, 5‐ c ]furazan)}‐2‐one‐11′‐oxide by a Diels‐Alder(D−A) type self‐cycloaddition, through the agency of an o ‐naphthoquinone nitrosomethide ( o ‐NQM). Moreover, 2‐hydroxy‐8‐methoxy‐1‐naphthaldehyde oxime was prepared and subjected to the same oxidation conditions. Its sterically guided result, 9‐methoxynaphtho[1, 2‐ d ]isoxazole, was isolated, instead of the expected spiro adduct. The peri intramolecular H bonding in the oxime is considered to have a key contribution to the outcome. Geometry and energy features of the oxidant‐ and stereo‐guided selectivity of both oxidation outcomes have been explored by DFT, perturbation theory and coupled cluster calculations. The reaction free energy of the D−A inter molecular cycloaddition is calculated at −82.0 kcal/mol, indicating its predominance over the intra molecular cyclization of ca . −37.6 kcal/mol. The cycloaddition is facilitated by NMMO through dipolar interactions and hydrogen bonding with both metal complexes and o ‐NQM. The 8( peri )‐OMe substitution of the reactant oxime sterically impedes formation of the spiro adduct, instead it undergoes a more facile cyclodehydration to the isoxazole structure by ca . 4.9 kcal/mol. Abstract : 2‐Hydroxy‐1‐naphthaldehyde oxime was oxidized by a D−A type self cycloaddition to spiro compound. Free reaction energy is calculated at −82.0 kcal/mol indicating its predominance over the intramolecular cyclization of −37.6 kcal/mol. 8‐methoxy substituted oxime is sterically guided to 9‐methoxynaphtho[1, 2‐d] instead of spiro adduct resulting to the formation of the isoxazole structure.