Reaction of Superoxide with Aci-Reductones

Abstract

Three reductones, 2,3-dihydroxy-4,4-diphenyl-2,5-cyclohexadien-l-one (11), 3,4-dihydroxycoumarin (35), and 3,4-dihydroxyspiro[5.5]undecan-3-en-4-one (64), were prepared and subsequently reacted with superoxide anion radical (02*-), generated from K02 and 18-crown-6 polyether. The reactions were carried out in aprotic media and quenched with methyl iodide which facilitates the trapping of the various oxyanions formed. While a plethora of products were formed in each case [2-hydroxy-2-methyl-4,4-diphenyl-5-cyclohexene-l,3-dione (17), dimethyl 4,4-diphenylglutaconate (18), methyl 4,4-diphenyl-3-butenoate ( 19), phenylcinnamaldehyde (20), methyl 3-phenylcinnamate ( 21), and benzophenone (22) from 11; 3-hydroxy-2-methoxycoumarin (39), 2-carbomethoxy-2-hydroxy-3coumaranone (40), 2-hydroxy-2-methyl-3-coumaranone (41), methyl o-hydroxyphenylglyoxylate (42), methyl salicylate (43), and catechol (44) from 35; and 2,4-dihydroxyspiro[5.5]undeca-l,4-dien-3one (66), 2-hydroxyspiro[4.5]dec-l-en-3-one (70), dimethyl 1,1-cyclohexanediacetate ( 73), and dimethyl a-keto-l-[(methoxycarbonyl)methyl]cyclohexane-l-propionate) (75) from 64], an overall analysis of the product distribution indicates that the basic elements of the reaction sequence are the same. The first step involves facile deprotonation and the concomitant generation of the reductone monoanion, a process which lends support to the suggestion of Afanas'ev and co-workers (Afanas'ev, I. B.; Grabovetskii, V. V.; Kuprianova, N. S. J. Chem. Soc. Perkin Trans. 2 1987, 281-285). Oxidation of this monoanion yields the corresponding triketone. Of the various options available to this polyketone, superoxide attack at the most electrophilic central carbonyl followed by oxidative cleavage and/or benzylic acid rearrangement are clearly the most prominent. These are followed by a variety of base catalyzed autoxidative processes which are highly dependent on the nature of the substrate.

Photochromism of o-Nitrophenyl-Substituted Oxazabicycles

“…Further, the diketo form 12a was found to be the major isomer in CDCl 3 , with a diketo to lactol ratio of approximately 10:1. This observation is in contrast to previous studies, which suggested that the lactol form of 1-(2-hydroxyphenyl)propane-1,2-dione is the major isomer in aprotic solvents.…”

Photochemical Cleavage and Release of Para-Substituted Phenols from α-Keto Amides

“…Conversion was essentially complete after 24 h at 25 °C. In the 13 C NMR spectra (CDCl 3 ) the characteristic feature of products 16a was a quaternary carbon at δ 98, which was very similar to quaternary carbon chemical shifts reported for model compounds 17 and 18 (vide infra). The structures proposed for 16a (Y = CH 3 , OCH 3 ) were also consistent with elemental analyses.…”

The Chemistry of Vicinal Polycarbonyl Compounds

“…Triones were assumed by Frimer et al to be intermediates in the superoxide oxidation of several dihydro derivatives of triones. See section III for similar experiments with tetraketone derivatives.…”