title: E versus Z diazeniumdiolation of acetoacetate-derived carbanions.
abstract: Nitric oxide adds to methyl acetoacetate in the presence of KOH in methanol at room temperature to form potassium acetylsydnonate N-oxide (K1) with an (E)-diazeniumdiolation and potassium acetate diazenium diolate (K(2)2) from a (Z)-diazeniumdiolation. A study of the reaction with LiOH, NaOH, and NMe(4)OH and with ethyl acetate substrate reveals that the temperature of the reaction greatly influences the nitric oxide reactivity. At 23 °C, nitric oxide adds to give both E and Z products, whereas at -5 °C the gas reacts almost exclusively to give Z addition. The (Z)-diazeniumdiolation products, namely, the alkali metal and NMe(4)(+) salts of methyl and ethylbutenoate-2-diazeniumdiolate-3-hydroxylate (3(2-) and 4(2-)), are isolated in good yields. The alkali metal salts are not amenable for recrystallization because of their ready decomposition in aqueous solutions. However, [NMe(4)](2)[MeC(O)C(N(2)O(2))CO(2)Me] is readily recrystallized from a methanol/acetonitrile solvent mixture. The crystals are unambiguously characterized by X-ray crystallography. NMR spectra for all of the 3(2-) and 4(2-) salts reveal the presence of two isomers in aq solutions. But the structure of the NMe(4)(+) salt contains only one of the isomers. Our attempts to cyclize the isolated and purified butenoatediazeniumdiolates from the (Z)-diazeniumdiolation to the E-containing sydnonate products were unsuccessful. TGA/DSC data for all of the products demonstrate the thermal instability of the salts at high temperatures. The salts decompose exothermally possibly with the release of N(2)O among other gases.
authors.affiliation: Department of Chemistry, University of Wyoming, 1000 East University Avenue, Laramie, Wyoming 82072-2000, USA. arulsamy@uwyo.edu
authors.forename: Navamoney
authors.initials: N
authors.lastname: Arulsamy
authors.forename: D Scott
authors.initials: DS
authors.lastname: Bohle
authors.forename: Carla L
authors.initials: CL
authors.lastname: Holman
authors.forename: Inna
authors.initials: I
authors.lastname: Perepichka
mesh_terms: D000090:Acetoacetates / Q000737:chemistry*; D000838:Anions / Q000737:chemistry; D018360:Crystallography, X-Ray; D006878:Hydroxides / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry; D010087:Oxides / Q000138:chemical synthesis / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000090:Acetoacetates; D000838:Anions; D006878:Hydroxides; D010087:Oxides; D017680:Potassium Compounds; D009569:Nitric Oxide; C005217:methyl acetoacetate; C029943:potassium hydroxide