1678-71-3Relevant articles and documents
Kinetics and mechanism of hydrolysis of 3-diazobenzofuran-2-one and its hydrolysis product (3-hydroxybenzofuran-2-one)
Chiang,Kresge,Meng
, p. 82 - 88 (2002)
Rates of acid-catalyzed hydrolysis of 3-diazobenzofuran-2-one, measured in concentrated aqueous perchloric acid and hydrochloric acid solutions, were found to correlate well with the Cox-Yates Xo excess acidity function, giving kH+ = 1.66 × 10-4 M-1 s-1, m? = 0.86 and kH+/kD+ = 2.04. The normal direction (kH/kD > 1) of this isotope effect indicates that hydrolysis occurs by rate-determining protonation of the substrate on its diazo-carbon atom. It was found previously that the next higher homolog of the present substrate, 4-diazoisochroman-3-one, also undergoes hydrolysis by this reaction mechanism but with a rate constant 15 times greater than that for the present substrate; this difference in reactivity can be understood in terms of the various resonance forms that contribute to the structures of these substrates. The product of the present hydrolysis reaction is 3-hydroxybenzofuran-2-one, which itself quickly undergoes subsequent acid-catalyzed hydrolysis to 2-hydroxymandelic acid. The acidity dependence of this subsequent hydrolysis is much shallower than that of the diazo compound precursor, and rates of reaction correlate as well with [H+] as with Xo. This is due in part to incursion of a nonproductive protonation on the hydroxy group of 3-hydroxybenzofuran-2-one that impedes hydrolysis and produces saturation of acid catalysis. Rates of hydrolysis of the hydroxy compound were also measured in dilute HClO4 and NaOH solutions as well as in CH3CO2H, H2PO4-, (CH2OH)3CNH3-, and NH4- buffers, and the rate profile constructed from these data showed the presence of uncatalyzed and hydroxide ion-catalyzed reactions. This hydroxide-ion catalysis became saturated at [NaOH] ? 0.05 M, implying occurrence of yet another nonproductive substrate ionization.
Photoreactions of 3-Diazo-3H-benzofuran-2-one; Dimerization and Hydrolysis of Its Primary Photoproduct, A Quinonoid Cumulenone: A Study by Time-Resolved Optical and Infrared Spectroscopy
Chiang, Yvonne,Gaplovsky, Martin,Kresge, A. Jerry,Leung, King Hung,Ley, Christian,Mac, Marek,Persy, Gabriele,Phillips, David L.,Popik, Vladimir V.,Roedig, Christoph,Wirz, Jakob,Zhu, Yu
, p. 12872 - 12880 (2007/10/03)
Light-induced deazotization of 3-diazo-3H-benzofuran-2-one (1) in solution is accompanied by facile (CO)-O bond cleavage yielding 6-(oxoethenylidene)-2,4-cyclohexadien-1-one (3), which appears with a rise time of 28 ps. The expected Wolff-rearrangement product, 7-oxabicyclo[4.2.0]octa-1,3,5-trien-8-ylidenemethanone (4), is not formed. The efficient light-induced formation of the quinonoid cumulenone 3 opens the way to determine the reactivity of a cumulenone in solution. The reaction kinetics of 3 were monitored by nanosecond flash photolysis with optical (λ max ≈ 460 nm) as well as Raman (1526 cm-1) and IR detection (2050 cm-1). Remarkably, the reactivity of 3 is that expected from its valence isomer, the cyclic carbene 3H-benzofuran-2-one-3-ylidene, 2. In aqueous solution, acid-catalyzed addition of water forms the lactone 3-hydroxy-3H-benzofuran-2-one (5). The reaction is initiated by protonation of the cumulenone on its β-carbon atom. In hexane, cumulenone 3 dimerizes to isoxindigo ((E)-[3,3′ ]bibenzofuranylidene-2,2′-dione, 7), coumestan (6H-benzofuro[3,2-c][1]benzopyran-6-one, 8), and a small amount of dibenzonaphthyrone ([1]benzopyrano[4,3-][1]benzopyran-5,11-dione, 9) at a nearly diffusion-controlled rate. Ab initio calculations (G3) are consistent with the observed data. Carbene 2 is predicted to have a singlet ground state, which undergoes very facile, strongly exothermic (irreversible) ring opening to the cumulenone 3. The calculated barrier to formation of 4 (Wolff-rearrangement) is prohibitive. DFT calculations indicate that protonation of 3 on the β-carbon is accompanied by cyclization to the protonated carbene 2H +, and that dimerization of 3 to 7 and 9 takes place in a single step with negligible activation energy.
Separation of 2- and 4-hydroxymandelic acid
Hoefnagel,Peters,Van Bekkum
, p. 353 - 356 (2007/10/03)
Hydroxyalkylation of phenol with glyoxylic acid, catalyzed by AlIII, results, under neutral aqueous conditions, in ortho-rich mixtures of hydroxymandelic acids. Para-rich mixtures of hydroxymandelic acids are obtained by ZnII catalysis under slightly alkaline conditions. A new separation method of these mixtures into the pure alkali salts of 2- and 4-hydroxymandelic acid is presented. Formation of a complex between the alkali ion and three co-operating oxygen atoms of 2-hydroxymandelate explains the excellent solubility of the ortho isomer in acetone, enabling extraction of this isomer selectively from mixtures of alkali salts of 2- and 4-hydroxymandelic acid.
