2.2.4.4- Tetramethyl-1,3-cyclobutanedione

The most obvious features of this synthesis are its simplicity and overall yield, which appear to be superior to those of any other published report. An important merit lies in the generality of the reaction, and the fact that it is an example of a reasonably large-scale photochemical preparation. Tetramethylethylene is readily produced from commercially available tetramethyl-1,3-cyclobutanedione by an identical route.7... 

The isomerization is usually complete in 5 hours and can easily be followed by vapor-phase chromatography. Heating periods up to 20 hours are not detrimental. The only failure among numerous preparations occurred when tetramethyl-1,3-cyclobutanedione contaminated with 4% of isobutyric acid was used. In case of partial conversion after 5 hours, additional increments (0.5 g.) of aluminum chloride should be added to complete the reaction. 

Tetramethyl-1,3-cyclobutanedione, reaction with aluminum chloride, 48,72... 

Irradiation of tetramethyl-1,3-cyclobutanedione in nonhydroxylic solvents results in decarbonylation as the major course of reaction with g-cleavage being observed as a minor reaction path. A low yield of the lactone [115] has also been reported (73) however, since this material might result from dimerization of dimethyl-ketene, it may not be a primary photoproduct (i.e., ketene dimer is isolated from irradiation of [69]. 

Hydrogenation of diketones to diols yields mixtures of stereoisomers. Tetramethyl-1,3-cyclobutanedione hydrogenates rapidly over Ru-on-carbon, nearly quantitative yielding an about equimolar mixture of the cis and rra s-diol ... 

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