Imidazoles. II. A General Synthesis for 1-Hydroxyimidazoles

Abstract

synthetic route to 1-hydroxyimidazoles. By selection of the starting materials substituents can be readily introduced into the 2,4 and/or 5 positions of the imidazole ring which is formed via the intermediacy of a gem-aminoalcohol. The reactions of the N-hydroxyl function are discussed.In a study of cellulosic fiber-polymer interactions4,5) we have been concerned with the synthesis of imidazoles6-9) and other polyaza heterocycles suitable for the attachment of vinylic moieties having differing reactivity ratios.10) Thus, although 4(5)-vinylimidazole has been described,11-15) the procedure is not amenable to facile variation and this alkene does not readily copolymerize with a wide range of monomens.13) Our attention was thus directed to the fact that almost exactly half a century ago Diels discovered16) that when aldehydes (RCHO) and butane-2,3-dione monoxime (I) are shaken with aqueous ammonia, a clan of compounds is formed by the elimination of two moles of water. Their reductive conversion into trisubstituted imidazoles (III) and their reversible hydrolysis to products considered to be the diols (IV) led16) to their formulation as II.Although the synthesis of the somewhat labile oxaziridine ring system has been achieved17,18) by several, usually oxidative, procedures, its generally limited stability in alkaline solutions and its apparent ease of formation in this alkaline condensation suggested that a re-examination of this group of products was merited.Repetition of the prescribed procedure smoothly afforded II in good yield. Examination of this compound then disclosed (for R=Ph) that IV is a simple hydrate of II and that the transformations

Synthesis and study of prototropic tautomerism of 2-(2-hydroxyphenyl)-1-hydroxyimidazoles

“…It is of interest that in the 1 H NMR spectrum one can observe the overlap of signals for two methyl groups (2.574 ppm and 2.571 ppm). At the same time the 13 A comparison of the 1 H NMR spectra of the model compounds (i.e., imidazole N-oxide 11 and 1-methoxyimidazole 16) reveals a difference in the chemical shifts of protons in position 6 of the hydroxyphenyl substituent (H6'). For imidazole N-oxide 11 this signal appears at 7.20 ppm.…”

“…[10][11][12][13][14][15] This discussion was summarized in A.R. Katrizky's paper 15 in which the results of previous papers have been considered.…”

“…1,[10][11][12][13][14][15][23][24][25] ) that 1-hydroxyimidazoles may exist in the two tautomeric forms (Scheme 1). Taking into consideration possible hydrogen M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT Tetrahedron 4 bonding in the molecules under study, the following utmost forms of the prototropic tautomers of 2-(2-hydroxyphenyl)substituted 1-hydroxyimidazoles 2-4 could be proposed: Scheme 7.…”

“…Tetrahedron 1213 C NMR (75.47 Hz, DMSO-d 6 ): δ= 158.1 (C=O), 157.5 (C2'), 141.1 (C2), 140.9 (C4), 131.7 (C4'), 126.4 (C6'), 119.3 (C5'), 117.2 (C3'), 115.1 (C5), 111.2 (C1'), 66.7 (OCH 3 ), 60.4 (OCH 2 CH 3 ), 15.3 (4-CH 3 ), 14.0 (OCH 2 CH 3 ) ppm. MS(EI): m/z=276[M] + .…”

Crystal Structures of 1-Hydroxyimidazole and Its Salts

“…Early reports on the preparation of 2,4,5-trisubstituted 1-hydroxyimidazoles [1][2][3] showed considerable uncertainty about the constitution of the product (an epoxide structure was assumed). Then, an unambiguous synthesis of 4,5-disubstituted 1-hydroxyimidazoles has been described [4].…”