A diketones, cyclic

ZnIMnO,), effects several known oxidations such as oxidation of alkynes to a-diketones, cyclic ethers to lactones, and cycloalkanones to dicarboxylic acids. The paper reports one novel transformation Oxidation of a cyclohexcne to a ketol in moderate yield (36%), equation (1). 

Polyfluorinated a-diketones react with 1,2-diainino compounds, such as ortlio-phenylenediamine, to give 2,3-substituted quinoxalmes [103] Furthermore, the carboxyl function of trifluoropyruvates offers an additional electrophilic center. Cyclic products are obtained with binucleophiles [13, 104] With aliphatic or aromatic 1,2-diamines, six-memhered heterocycles are formed Anilines and phenols undergo C-alkylation with trifluoropyruvates in the ortho position followed by ring closure to form y-lactams and y-lactones [11, 13, 52, 53, 54] (equation 23). 

Infrared and nuclear magnetic resonance spectral evidence led Kendall and Hajos to conclude that furan-3,4-dione (37) exists as such, which is surprising since cyclic a-diketones with five-membered rings are usually monoenolized. The 2,5-dicarbethoxy derivative 38 was earlier stated to exist in the dihydroxy form. ... 

For the latter case an acid-catalyzed decomposition of intermediate 4 is assumed to give the carbonyl products 2 and 3, or a diketone as shown above, without going through a cyclic intermediate ... 

They have also carried out the oxidation of selinene by means of ozone and potassium permanganate and have thus been able to establish that the regenerated selinene is not absolutely identical with the natural selinene. They are the first to record the existence of a hemi-cyclic-sesquiterpene this compound is termed pseudo-()3)-selinene. By passing a current of ozone into a solution of natural selinene (pseudo-( 8)-selinene). in acetic acid, there is obtained a diketone, CjjHogOj, which is purified by treatment with permanganate in acetone solution. Its properties are as. follows —... 

Cyclic 1,2-diamines are cleaved to diketones with dimethyl dioxirane. a-Diketones and a-hydroxy ketones are also cleaved by alkaline H202. HIO4 has... 

Certain other combinations of adjacent functional groups are also cleaved by periodate. Diketones are cleaved to carboxylic acids, and it is proposed that a reactive cyclic intermediate is formed by nucleophilic attack on the diketone.263... 

These developments are derived from the early work of Ramirez and coworkers16 17, which was concerned with the formation of a type of cyclic oxyphosphorane that is formed by the addition of a trialkyl phosphite to either a diketone (Figure 5.8) or an a, 3-imsaturated carbonyl compound (Figure 5.9). Initially, developments from this effort... 

Aldol reactions are often used to close five- and six-membered rings. Because of the favorable entropy (p. 211), such ring closures generally take place with ease, even where a ketone condenses with a ketone. An important example is the Robinson annulation reaction which has often been used in the synthesis of steroids and terpenes. In this reaction a cyclic ketone is converted to another cyclic ketone, with one additional six-membered ring containing a double bond. The substrate is treated with methyl vinyl ketone (or a simple derivative of methyl vinyl ketone) and a base.551 The enolate ion of the substrate adds to the methyl vinyl ketone in a Michael reaction (5-17) to give a diketone that undergoes or... 

The earliest methods for preparing cyclic a-diazo ketones involved the oxidation of the monohydrazones prepared from a-diketones, generally using mercuric oxide.7,8 Recent modifications of this procedure include the use of calcium hypochlorite in aqueous sodium hydroxide or activated manganese dioxide as oxidants.1 The latter reagent, especially, hoc ms preferable to mercuric oxide. The base-catalyzed decomposition of tile monotosylhydrazoneH of a-diketones has been... 

JOC 47 2820 (1982) (/1-diketones to hydroxy ketones) 50 127 (fi-keto carboxylate), 3411 (fi-diketones to hydroxy ketones) (1985) 51 1253 (2,2-dithioalkan-l-ones), 2795 (a-flooro ketones) (1986) 52192 (fi-keto esters), 256,1141,1359 (fi-keto esters), 2036 (/1-diketones to hydroxy ketones), 2086 (a-acetoxy ketone), 2244 (fi-keto ester), 3223 (cyclic /1-diketones to hydroxy ketones), 4363 (y- arid 5-keto acids) (1987) 53 860, 1969, 2589 (x-keto ester), 4405 (a-acyloxy ketone), 4962 (1988) 54 2238 (/S-diketone to fi-hydroxy ketone), 2274, 3221 (a-diketone to a-hydroxy ketone) (1989) 55 3917 (1990)... 

Condensation of 4,5-diaminoacenaphthene with cyclic a-diketones (acenaphthenequinone, phenanthrenequinone) gives rise to b-side anne-lated acenaphtho [4,5- >/]-l,4-diazepine derivatives 523 (IICB2852 ... 

Ordinarily, only the keto form of o-diketones such as 2,3-butanedione is seen in NMR spectra. However, if the enol form of an a-diketone is stabilized by hydrogen bonding-as in the following cyclic a-diketones— only the stabilized enol form appears in the NMR spectra. 

---