Cycloalkane-1,3-dione

Preparation of 2-Cycloalkenones and Cycloalkane-1,3-diones BY Iron(III) Chloride-Induced Ring Opening of 1-Trimethyi,-siLYLOxY- AND 1,2-Bis(trimethylsilyloxy)bicyclo[w.1.0]alkanes... 

In the Diels-Alder reaction with inverse electron demand, the overlap of the LUMO of the 1-oxa-l,3-butadiene with the HOMO of the dienophile is dominant. Since the electron-withdrawing group at the oxabutadiene at the 3-position lowers its LUMO dramatically, the cycloaddition as well as the condensation usually take place at room or slightly elevated temperature. There is actually no restriction for the aldehydes. Thus, aromatic, heteroaromatic, saturated aliphatic and unsaturated aliphatic aldehydes may be used. For example, a-oxocarbocylic esters or 1,2-dike-tones for instance have been employed as ketones. Furthermore, 1,3-dicarbonyl compounds cyclic and acyclic substances such as Meldmm s acid, barbituric acid and derivates, coumarins, any type of cycloalkane-1,3-dione, (1-ketoesters, and 1,3-diones as well as their phosphorus, nitrogen and sulfur analogues, can also be ap-... 

The bis(trimethylsiloxy)bicyclo[n.l.O]alkane 231 undergoes the FeCl3-induced ring expansion to the cycloalkane-1,3-dione 232. This method has been applied to the synthesis of macrocyclic tetraketones [128]. (Scheme 92)... 

Products of ethylation and methylation of enolates of cycloalkane-1,3-diones with ring sizes 7-10 have been studied under a variety of alkylating reagent-solvent systems. Decrease in the 0 C alkylation ratios with increase in ring size is believed to be a consequence of greater steric strain in the conjugated enolate resonance contributor and consequent diminution in the proportion of D-attack. 

In solution, open-chain 1,3-dicarbonyl compounds enolize practically exclusively to the czls-enolic form (4b), which is stabilized by intramolecular hydrogen bonding. In contrast, cyclic 1,3-dicarbonyl compounds e.g. cycloalkane-1,3-diones [46]), can give either trans-Qnols (for small rings) or czk-enols (for large rings). As the diketo form is usually more dipolar than the chelated cu-enolic form, the keto/enol ratio often depends on solvent polarity. This will be discussed in more detail for the cases of ethyl acetoacetate and acetylacetone [47-50, 134, 135]. 

Similar reactions with bis(trimethylsiloxy)bicyclo[4.1.0]alkanes afford cycloalkane-1,3 diones . ... 

The synthesis of cycloalkane-1,3-diones starts from bis(trimethylsilyloxy) bicyclo[n.l.O]alkanes and FeCl3, followed by treatment with Na02CCH3 in MeOH (Equation (lO)) 60... 

B. Eistert, G. Kilpper, and J. Goring, The reaction of cycloalkane-1,3-diones with hydrazine, Chem. Ber., 102(1969) 1379-1396. 

This homologation has been applied to bis(triracthyIsilyloxy)bicyclo[n.l.O]-alkancs (4) to obtain cycloalkane-1,3-diones (5) in moderate yields (two examples 68 and 727 ).i... 

Cyclic anhydrides, 99 Cycloalkane-1,3-diones, 154 Cydoalkanoic acids, 138 Cycloalkcncs, 298... 

N-condensed 19, 463 cycloalkane-1,3-diones, 2-acyl- 19, 841 dicarboxylic acid chloride esters 17, 619... 

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