New spirocyclic nitroxides of 2,5-dihydroimidazole series flanked by two mesogenic fragments

Abstract

N/C-Hydroxylated spirofused derivatives of 2,5-dihydroimidazole which were synthesized by condensation of 4-(4-hydroxyphenyl)cyclohexanone with aryl hydroxylaminoalkyl ketones in the presence of ammonia were determined to be trans-ee-isomers of 1,4-cyclohexane framework by NMR spectroscopy. Oxidation of the cyclic hydroxylamino moiety followed by acylation of the phenolic hydroxyl group with 4-alkyloxybenzoic acid chlorides led to the corresponding spirocyclic nitroxides bearing two mesogenic fragments.

The synthesis of new functionalized 1,3,5-triazine-based stable bi- and trinitroxides of the 2,5-dihydroimidazole series

“…In our previous publication, 8 was found to have a trans-ee-configuration. 36 Because the corresponding chemical shifts and coupling constants (see the Experimental section) of 7 were identical to those obtained for debenzylated analogue 8, we assigned the structure of a trans-ee-isomer to 7. Oxidation of hydroxylamine 7 with manganese dioxide in chloroform gave nitroxide 9 with an 80% yield.…”

“…4-(4-Hydroxyphenyl)cyclohexanone (6) was purchased from Aldrich. 3-(4-Hydroxyphenyl)-2,2-dimethyl-1,4-diazaspiro[4.5]dec-3-ene-1-oxyl (3), 34 1-(4benzyloxyphenyl)-2-(hydroxylamino)-2-methyl-1-propanone hydrochloride (5), 35 3-(4-benzyloxyphenyl)-2,2dimethyl-1,4-diazaspiro[4.5]dec-3-ene-8-ol 1-oxyl (11), 36 3,4,5-tris(dodecyloxy)benzoic acid, 40 and 1-methoxy-3,5-dichloro-1,3,5-triazine 41 were obtained by the procedures described in the literature.…”

“…33 The present report continues our research on the synthesis of functional derivatives of spirocyclic monoand oligoradicals of the azole series. [34][35][36] The present paper describes the synthesis as well as structural characterization of new paramagnetic derivatives of 2,4,6-tris(aryloxy)-1,3,5-triazine (1a-c) and of 2,4bis(aryloxy)-6-methoxy-1,3,5-triazine (2a-c; Figure 1).…”

Spirocyclic Nitroxides as Versatile Tools in Modern Natural Sciences: From Synthesis to Applications. Part I. Old and New Synthetic Approaches to Spirocyclic Nitroxyl Radicals

“…HAK 250 (R = H), bearing an additional functional phenolic group, has been employed for the synthesis of SNRs possessing one or two mesogenic groups. For this purpose, compounds 250 (R = H, C n H 2n+1 ) are condensed with a cycloxexanone [ 157 ] or with its four-substituted functional derivatives, 4-(4-hydroxyphenyl)cyclohexanone [ 158 ] and 4-hydroxycyclohexanone [ 159 ]. After the oxidation of intermediate N -hydroxy derivatives to SNRs 251 , the latter are acylated by means of one or two residues of 4-alkoxybenzoic acids to form corresponding paramagnetic esters 252 (one of examples is shown in Scheme 44 ).…”