[1515-75-9] · C6H8O2 · (E)-Methyl 2,4-Pentadienoate · (MW 112.14)
(electron-poor diene capable of cycloaddition reactions with activated dienophiles to form carbocyclic1 and heterocyclic2 compounds; metal-promoted [6 + 4] cycloadditions3 and metal-promoted chain extensions4)
Physical Data: bp 55-57 °C/14 mmHg.
Solubility: sol most organic solvents.
Form Supplied in: colorless liquid.
Analysis of Reagent Purity: NMR.
Handling, Storage, and Precautions: polymerizes easily.
As an electron-poor diene, the cycloaddition reactions of (E)-methyl 2,4-pentadienoate are optimal when combined with electron-rich dienophiles such as enamines (eq 1).1 When electron-deficient dienophiles such as benzyljuglone,7 or relatively nonpolarized dienophiles are employed (eq 2),8 more forcing conditions are needed.
Nitroso compounds can react with the dienoate to afford 3,6-dihydro-1,2-oxazines (eq 3).2 The 3,4-double bond can act as a 2p component in reactions with diphenylnitrilimine (eq 4).9
The diene is a useful acceptor in the Heck reaction (eq 5).4 It should be noted that the metal acts in a catalytic fashion in this reaction. When other reactants are not included in the reaction mixture, dimerization and further oligomerization is observed.10-12 Other metal-promoted reactions can induce cycloaddition processes. In a noncatalytic process, complexation of thiepin dioxide with chromium tricarbonyl brings about [6 + 4] cycloaddition (eq 6).3
Richard T. Taylor
Miami University, Oxford, OH, USA