96506-59-1

The present contribution describes the synthesis and characterization of a family of robust ruthenium complexes, supported by a tridentate pincer ligand of the type bis-phenolate-N-heterocyclic carbene [ tBu(OCO) 2-] (NHC). Ruthenium(II) complexes (1-3) bearing bis-phenolate-N-heterocyclic carbene ligand were synthesized in good yields by the reaction of imidazolinium proligand (HL) with metal precursors [RuHCl(CO)(EPh3)2(B)] (E = P or As; B = PPh3, AsPh3 or Py) by transmetalation from the corresponding silver carbene complex. All the Ru(II)-NHC complexes have been characterized by elemental analyses, spectroscopic methods as well as ESI mass spectrometry. Based on the spectral results, an octahedral geometry was assigned for all the complexes. The tridentate nature of the tBu(OCO) 2- ligand as well as some level of steric protection provided by the t Bu groups may rationalize the excellent stability of the Ru-Ccarbene bond in the present systems. Moreover, for the explorations of catalytic potential of the synthesized compounds, all the three [Ru-NHC] complexes (1-3) were tested as catalysts for amidation of alcohols with amines. Notably, the complex 1 was found to be very efficient and versatile catalyst towards amidation of a wide range of alcohols with amines. [Figure not available: see fulltext.].

Alkylated 1,3-benzodioxane, 1,3-benzoxathiole, o-aminophenols, and 2,3-dihydro-1,3-benzoxazoles were obtained from 3,5-di-tert-butylbenzene-1,2-diol. The antiradical and antioxidant activities of these compounds were examined in the model oxidation of hexane, initiated by γ irradation. The antiradical activity of the ortho analog of tocopherol with a five-membered ring, 7-hydroxy-4,6-di-tert-butyl-1,3-benzoxathiole-2-thione, exceeds fourfold that of the six-membered analog, 8-hydroxy-5,7-di-tert-butyl-1,3-benzodioxane.

The reaction of sterically hindered 1,2- and 1,4-benzoquinones with aliphatic amines leads to sterically hindered 1,2- and 1,4-aminophenols.