E versus Z Diazeniumdiolation of Acetoacetate-Derived Carbanions

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• 作者：Navamoney Arulsamy ; D. Scott Bohle ; Carla L. Holman ; Inna Perepichka
• 刊名：The Journal of Organic Chemistry
• 出版年：2012
• 出版时间：September 7, 2012
• 年：2012
• 卷：77
• 期：17
• 页码：7313-7318
• 全文大小：279K
• 年卷期：v.77,no.17(September 7, 2012)
• ISSN：1520-6904

文摘

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 (K₂2) from a (Z)-diazeniumdiolation. A study of the reaction with LiOH, NaOH, and NMe₄OH and with ethyl acetate substrate reveals that the temperature of the reaction greatly influences the nitric oxide reactivity. At 23 掳C, nitric oxide adds to give both E and Z products, whereas at 鈭? 掳C the gas reacts almost exclusively to give Z addition. The (Z)-diazeniumdiolation products, namely, the alkali metal and NMe₄⁺ salts of methyl and ethylbutenoate-2-diazeniumdiolate-3-hydroxylate (3^2鈥?/b> and 4^{2鈥?/sup>), are isolated in good yields. The alkali metal salts are not amenable for recrystallization because of their ready decomposition in aqueous solutions. However, [NMe₄]₂[MeC(O)C(N₂O₂)CO₂Me] is readily recrystallized from a methanol/acetonitrile solvent mixture. The crystals are unambiguously characterized by X-ray crystallography. NMR spectra for all of the 32鈥?/b> and 42鈥?/b> salts reveal the presence of two isomers in aq solutions. But the structure of the NMe₄+ 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 N₂O among other gases.}