Preparation and Selected Reactions oft-Butyl 2-Methylene-3-oxoalkanoates

✍ Scribed by Martin, H. ;Hoffmann, R. ;Gassner, Andreas ;Eggert, Ulrike

• Publisher: Wiley (John Wiley & Sons)
• Year: 1991
• Tongue: English
• Weight: 699 KB
• Volume: 124
• Category: Article
• ISSN: 0009-2940
• DOI: 10.1002/cber.19911241118

✦ Synopsis

The title class of 1,l-diactivated ethylenes has been prepared in two steps from aldehydes and t-butyl acrylate by (i) DABCO-catalyzed coupling to give t-butyl 2-(hydroxyalky1)-2-propenoates 11 and (ii) low-temperature Jones oxidation, followed by swift work up at low temperature. The resulting t-butyl 2-methylene-3-oxoalkanoates 12 are stabilized by sterically demanding and also by aromatic groups R. For primary unhindered alkyl groups, stability is low. The compounds enter into Michael reactions, hetero Diels-Alder additions with enol ethers, and self-dimerization.

2-Methylene-l,3-dicarbonyl compounds have been of interest For a long time. More than 100 years ago W. H. Perkin, Jr., suggested a low-boiling fraction of the reaction of formaldehyde with malonic esterla,C'. Diester 1 is a plausible intermediate en route to the teformaldehyde with malonic esters was investigated by Bachman and Tanner2) and also by R ~b e r t s ~" ~) , who showed that the bulky di-t-butyl 2-methylenemalonate (4 R = R' = t-butyl) can be handled more readily than simple ester analogs. Recently, a variety of a-methylenemalonic esters was obtained by retro Diels-Alder reaction (3 -+ 4)4).