Cycloalkanes reaction with 3-ketoesters

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-... 

In a seminal contribution, C.-J. Li reported in 2007 the first iron-catalyzed CDC reaction between alkanes and activated methylene derivatives such as p-ketoesters or p-diketones. A simple FeCl2 catalytic system (20 mol%) can promote the coupling reaction in the presence of 2 equiv. of di-fert-butyl peroxide ( BuOO Bu) as the oxidant in an alkane as the solvent (Scheme 4.2). The CDC reaction is efficient with cycloalkanes and p-ketoesters (48-88% yields). It is worth mentioning that linear alkanes such as n-hexane produce moderate yields (42%) with a mixture of two regio-isomers in a 1.2 1 ratio. By contrast, the reaction with p-diketones is a more difficult task, and only low yields (10-15%) are obtained. 

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