Synthesis and characterization of two dehydroacetic acid derivatives and molybdenum(V) complexes: an NMR and crystallographic study

Two enaminones ethyl 4-(4-hydroxy-6-methyl-2H-pyran-2-on-3-yl)-2-(tryptamino)-4-oxo-2-butenoate (HL1) and 3-(1-tryptaminoetylidene)- 6-methyl-2H-pyran-2,4(3H)-dione (HL2) have been prepared by the reactions of tryptamine with 2-hydroxy-4-(4-hydroxy)-6- methyl)-2Hbb-pyrane-2-on-3-yl)-4-oxo-2-butenoate (ehmpb) or with dehydroacetic acid (dha). The NMR spectroscopy confirmed that both tautomeric forms of HL1: endo-enol (tautomer A with hydroxyl group at position 4) and exo-enol form (tautomer B with hydroxyl group at position 7) are present in the DMSO-d6 solution. The molecular and crystal structure as well as the NMR data of HL2 showed that the condensation of dha and tryptamine occurs at acetyl-carbonyl and not at the pyrone-carbonyl group. Also new dinuclear [Mo2O4(L1)2(CH3OH)2] (1) and hexanuclear molybdenum(V) complexes (C10H12NH)[Mo6O12(OCH3)4(acac)3] (2) have been prepared by the reactions of [Mo2O3(acac)4] (acac ¼ acetilacetonate ion) with HL1 or with tryptamine. All compounds have been characterized also by means of elemental analyses, IR spectroscopy as well as by thermal analyses. q 2004 Elsevier B.V. All rights reserved.